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ARTIGOS 
 
Abdominal Muscle Response During
Curl-ups on Both Stable and
Labile Surfaces
Background and Purpose. With the current interest in stability training for
the injured low back, the use of labile (movable) surfaces, underneath the
subject, to challenge the motor control system is becoming more popular.
Little is known about the modulating effects of these surfaces on muscle
activity. The purpose of this study was to establish the degree of
modulating influence of the type of surface (whether stable or labile) on
the mechanics of the abdominal wall. In this study, the amplitude of
muscle activity together with the way that the muscles coactivated due to
the type of surface under the subject were of interest. Subjects. Eight men
(mean age523.3 years [SD54.3], mean height5177.6 cm [SD53.4],
mean weight572.6 kg [SD58.7]) volunteered to participate in the study.
All subjects were in good health and reported no incidence of acute or
chronic low back injury or prolonged back pain prior to this experiment.
Methods. All subjects were requested to perform 4 different curl-up
exercises—1 on a stable surface and the other 3 on varying labile surfaces.
Electromyographic signals were recorded from 4 different abdominal
sites on the right and left sides of the body and normalized to maximal
voluntary contraction (MVC) amplitudes. Results. Performing curl-up
exercises on labile surfaces increased abdominal muscle activity (eg, for
curl-up on a stable surface, rectus abdominis muscle activity was 21% of MVC
and external oblique muscle activity was 5% of MVC; for curl-up with the
upper torso on a labile ball, rectus abdominis muscle activity was 35% of
MVC and external oblique muscle activity was 10% of MVC). Furthermore,
it appears that increases in external oblique muscle activity were larger than
those of other abdominal muscles. Conclusion and Discussion. Performing
curl-ups on labile surfaces changes both the level of muscle activity and the
way that the muscles coactivate to stabilize the spine and the whole body. This
finding suggests a much higher demand on the motor control system, which
may be desirable for specific stages in a rehabilitation program. [Vera-Garcia
FJ, Grenier SG, McGill SM. Abdominal muscle response during curl-ups on
both stable and labile surfaces. Phys Ther. 2000;80:564–569.]
Key Words: Abdominal muscle, Gym ball, Low back, Rehabilitation, Stable/labile, Swiss ball.
564 Physical Therapy . Volume 80 . Number 6 . June 2000
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Francisco J Vera-Garcia
Sylvain G Grenier
Stuart M McGill
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T
he use of labile (movable) surfaces underneath
the subject for stability training of the injured
low back is becoming more popular.1 Recent
work has demonstrated the importance of the
abdominal muscles in ensuring sufficient spine stability
to prevent buckling and enhancing function.2–4 The
optimal muscle recruitment schemes chosen by the
motor control system determine the resultant stability
together with the spine load that results from active
muscle forces. In our view, clinical issues include the
need to understand the effects of using labile surfaces to
challenge the muscular system during rehabilitative
exercise.
In order to choose the most appropriate exercises, we
contend that data are needed on activation of the
muscles that collectively form the abdominal wall during
tasks performed on labile surfaces. Some work that our
group conducted, which involved implanting intramus-
cular electrodes into the components of the abdominal
wall, supported the impression that the rectus abdominis
muscle is recruited primarily to create trunk flexion,
whereas the obliques are recruited for a variety of
reasons (eg, to enhance spine stability,2 to assist chal-
lenged breathing during exercise or due to disease,5 to
generate lateral bending and twisting torque6). Some
work has been conducted to document the loads
imposed on the spine during various abdominal exercis-
es,7 but the effect of labile surfaces was not examined.
However, the curl-up (as described by McGill1), as an
abdominal exercise, has been shown to produce reason-
able levels of activity in the rectus abdominis muscle
while minimizing the resultant spine load and has been
adapted into several low back fitness programs (for
example, see McGill8).
The next stage in developing the scientific foundation is
to document the degree of modulating influence of the
type of surface (whether stable or labile) on the mechan-
ics of the abdominal wall. Specifically, in this study, the
amplitude of muscle activity and the way that the muscles
were coactivated due to the type of surface under the
subject were of interest.
FJ Vera-Garcia, is a graduate student, Department of Morphological Science, Faculty of Medicine and Odontology, University of Valencia, 46015,
Valencia, Spain.
SG Grenier, MA, is a doctoral student, Occupational Biomechanics and Safety Laboratories, Faculty of Applied Health Sciences, Department of
Kinesiology, University of Waterloo, Waterloo, Ontario, Canada.
SM McGill, PhD, is Professor, Occupational Biomechanics and Safety Laboratories, Faculty of Applied Health Sciences, Department of Kinesiology,
University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 (mcgill@healthy.uwaterloo.ca). Address all correspondence to Dr McGill.
All authors provided concept/research design, writing, and data analysis. Mr Vera-Garcia and Mr Grenier provided data collection. Dr McGill and
Mr Vera-Garcia provided subjects and project management. Dr McGill provided facilities/equipment and fund procurement.
The test protocol was approved by the University of Waterloo Office of Human Research Ethics Committee.
This study was made possible by financial support of the Natural Sciences and Engineering Research Council (Canada). Mr Vera-Garcia was
supported by a visiting scholars grant (University of Valencia, Spain).
This article was submitted May 3, 1999, and was accepted February 18, 2000.
Physical Therapy . Volume 80 . Number 6 . June 2000 Vera-Garcia et al . 565
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Method
Subjects
Eight men (mean age523.3 years [SD54.3], mean
height5177.6 cm [SD53.4], mean weight572.6 kg
[SD58.7]) volunteered to participate in this study. All
subjects were in good health and reported no history of
acute or chronic low back injury or prolonged episodes
of back pain prior to this experiment. Their history of
abdominal muscle exercising was neither investigated
nor controlled. Subjects completed an information and
“informed consent” document approved by the Univer-
sity of Waterloo Office of Research.
Tasks
All subjects were requested to perform 4 different
curl-up exercises. The subjects were familiarized with the
4 tasks. The first task (task A) was to do a traditional
curl-up on a padded bench with the subject’s feet flat on
the bench surface and both knees and hips flexed
(Fig. 1). The subject’s hands were placed behind the
head, and just the head and shoulders were elevated
from the bench surface. This was considered to be a
stable surface. The next 3 tasks varied based on the type
of labile surface. For the second task (task B), the
subject’s torso was supported over a gym ball and the
feet were placed flat on the floor. Ball inflation was
checked between subjects to ensure that the diameter
remained at 70 cm prior to each test. For the third task
(task C), the subject’s feet rested on a bench at the same
height as the ball. For the fourth task (task D), the ball
was replaced with a round wobble board with 3 degrees
of freedom,with a 50 milli-
second (msec) time reference. Peak amplitudes were 
averaged over a 100 msec window of time, 50 msec 
prior to peak and 50 msec after the peak.
side,4 per standard EMG protocol.24 In order to ensure 
consistent electrode placement throughout testing, 
electrodes were secured with surgical tape. Place-
ment was confirmed by viewing EMG signals while 
separately activating each muscle. Subjects then per-
formed a sub-maximal warm-up for five minutes on a 
stationary bicycle while watching a brief video of the 
exercises to be performed in order to familiarize sub-
jects with exercise technique. A five-second MVIC 
was performed three times in the standard manual 
muscle testing protocol positions for each gluteal 
muscle18,19 with one minute of rest between each con-
traction. A strap was secured around the distal femur 
during muscle testing for both muscles to ensure 
standardization of resistance (Figure 1). Verbal encour-
agement was given with each trial.
Exercise order was randomized using a random pat-
tern generator25 in order to avoid any order bias due 
to fatigue. Subjects were barefoot while performing 
exercises to prevent any potential variations that may 
have occurred due to footwear. Two minutes of rest 
was given between the performance of each exercise. 
Subjects performed eight repetitions of each exercise, 
three practice repetitions and five repetitions that 
were used for data collection. Exercises were per-
formed to a metronome set at 60 beats per minute to 
standardize the rate of movement across subjects. 
To replicate a clinical setting, researchers chose to 
use visual analysis of movement to ensure proper 
exercise technique rather than an electrogoniometer 
or movement analysis software since both of these 
Figure 1. Maximum voluntary isometric contraction testing 
example set up.
Figure 2. CorTexTM equipment (Performance Dynamics, 
San Diego, CA).
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 210
To determine MVIC, the middle 3/5ths time for each 
manual muscle test trial was isolated and the peak value 
determined. The highest peak value out of the three tri-
als was recorded and determined to be the MVIC.
In order to establish %MVIC for each exercise per-
formed by an individual subject, data were collected 
for the last five repetitions of each exercise. If the 
EMG data were clearly cyclic, the middle three repeti-
tions were analyzed. If it was difficult to determine 
when a repetition started and stopped on visual anal-
ysis of EMG data, then the middle 3/5ths of the total 
time to perform the five repetitions was analyzed. 
The highest peak out of the three repetitions was then 
divided by MVIC to yield %MVIC for that individual. 
To determine %MVIC values for rank ordering of 
exercises, the %MVIC for each muscle was averaged 
between all subjects for each exercise. 
RESULTS 
Twenty-four subjects satisfied all eligibility criteria 
and consented to participate in the research study. 
Data from one subject were excluded due to faulty 
data from the EMG leads for both muscles, and data 
from another subject were excluded due to faulty data 
from the EMG lead for gluteus maximus only. There 
were a few other isolated instances of faulty data from 
EMG leads, in which case the subject’s data were 
excluded from analysis for that specific exercise. The 
number of subjects included in data analysis for each 
exercise can be referenced in Tables 4 and 5. Due to 
the advanced level of some of the exercises included 
in the current study, such as single limb bridge on 
unstable surface and side plank, some subjects were 
unable to successfully complete all exercises. In these 
instances, subject data were not included in data anal-
ysis for that specific exercise. Peak amplitudes, 
Table 4. Results for Gluteus Medius recruitment, %MVIC and rank for all exercises.
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 211
expressed as %MVIC for gluteus medius and gluteus 
maximus, are rank ordered in Tables 4 and 5. Five of 
the exercises produced greater than 70%MVIC of the 
gluteus medius muscle. In rank order from highest 
EMG value to lowest, these exercises were: side plank 
abduction with dominant leg on bottom (103%MVIC), 
side plank abduction with dominant leg on top 
(89%MVIC), single limb squat (82%MVIC), clamshell 
(hip clam) progression 4 (77%MVIC), and font plank 
with hip extension (75%MVIC). Five of the exercises 
recruited gluteus maximus with values greater than 
70%MVIC. In rank order from highest EMG value to 
lowest, these exercises were: front plank with hip 
extension (106%MVIC), gluteal squeeze (81%MVIC), 
side plank abduction with dominant leg on top 
(73%MVIC), side plank abduction with dominant leg 
on bottom (71%MVIC), and single limb squat 
(71%MVIC). Table 6 displays the exercises that 
Table 6. Top exercises for muscle activation of both gluteus medius and gluteus maximus (>70% MVIC).
Table 5. Results for Gluteus Maximus recruitment, %MVIC and rank for all exercises.
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 212
produced greater than 70%MVIC for both gluteus 
medius and maximus muscles. These exercises 
included front plank with hip extension (75%MVIC, 
106%MVIC), side plank abduction with dominant leg 
on top (89%MVIC, 73%MVIC), side plank abduction 
with dominant leg on bottom (103%MVIC, 71%MVIC), 
and single limb squat (82%MVIC, 71%MVIC) for glu-
teus medius and maximus respectively.
DISCUSSION
The main objective of this study was to examine 
muscle activity during common clinical exercises 
used to strengthen the gluteus medius and gluteus 
maximus muscles. This study sought to analyze and 
compare information reported in previous studies 
by Distefano, Bolga, and Ayotte regarding ranking of 
various therapeutic exercises using %MVIC. The sec-
ondary objective was to describe %MVIC for other 
commonly used therapeutic exercises not previously 
reported upon. The authors of this study chose to 
examine peak amplitude averaged over a 100 ms win-
dow, 50 ms prior to peak and 50 ms after the peak, 
during repetitions five, six and seven, the highest of 
which was converted to %MVIC. This methodology 
is similar to studies by both Distefano3 and Bolgla.4 
Ayotte et al. averaged EMG activity over a 1.5 sec 
window during the concentric phase of each exer-
cise.5 Due to slight differences in data collection and 
data analysis between the current study, and studies 
conducted by Distefano, Bolgla and Ayotte, interpre-
tation of results and similarities across studies will 
predominantly address the sequence of rank order as 
opposed to absolute values for the %MVIC.3,4,5 
There were two exercises where %MVIC was found to 
be higher than MVIC, side plank abduction with domi-
nant leg down (103%MVIC) for gluteus medius and 
front plank with hip extension (106%MVIC) for glu-
teus maximus. There are several possibilities as to why 
these findings may have occurred. One possibility is 
that subjects lacked sufficient motivation to perform a 
true maximal contraction during MVIC testing, despite 
the fact that verbal encouragement was given to all 
subjects during max testing of both muscles. Another 
possibility is that subjects were not able to truly give a 
maximum effort during the manual muscle test. 
Authors of previous research have reported that in 
order to obtain a true maximum contraction, it is nec-
essary to superimpose an interpolated twitch, which is 
an electrically stimulated contraction, on top of the 
maximum voluntary contraction.26 Current research in 
electrophysiology is further examining this phenome-
non with mixed results regarding sensitivity of various 
interpolated twitch techniques, differences in method-
ology, and interpretation of their results.27,28,29 Future 
researchers using MVIC for standardization across sub-
jects shouldfollow this research closely in order to 
ensure the most accurate methodology is used for 
establishing maximal voluntary muscle contractions. 
A final possibility is that with these exercises there was 
substantial co-contraction of the core musculature, 
which may have led to higher values than could be 
obtained during isolated volitional contraction. In the 
MMT positions used to establish MVIC the pelvis is 
stabilized against the surface of the table with relatively 
isolated muscle recruitment. In both of the above 
mentioned exercises, the pelvis does not have external 
support and higher EMG values could reflect increased 
activity due to an increased need for stabilization 
resulting in synergistic co-contraction. Future research 
may need to examine differences in muscle recruit-
ment and activation patterns in exercises that test iso-
lated muscle function versus ones that require core 
stabilization resulting in co-contraction.
Gluteus Medius
Table 7 depicts the top gluteus medius exercises deter-
mined by the authors of the current study as refer-
enced to the exercises examined in studies performed 
by Distefano,3 Bolgla,4 and Ayotte.5 The authors of the 
current study found highest %MVIC peak values for 
side plank abduction with dominant leg on bottom 
(103%MVIC), side plank abduction with dominant leg 
on top (89%MVIC), single limb squat (82%MVIC), 
clamshell progression 4 (77%MVIC), and front plank 
(75%MVIC) as outlined in Table 7. Four of the top five 
exercises were not previously examined by Distefano,3 
Bolga,4 or Ayotte.5 All of these exercises exhibited 
greater than 70%MVIC, the peak amplitude necessary 
for enhancement of strength, suggesting they may 
have benefits for gluteus medius strengthening. How-
ever, these exercises are all very challenging and 
would not be appropriate for initial strengthening in 
patients with weak core musculature due to their high 
degree of difficulty and the amount of core stabiliza-
tion required. The possible exception may be clam-
shell progression 4, due to the stabilization provided to 
the subject when lying on the floor to perform the 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 213
exercise. While the top exercises in this study produced 
the greatest peak amplitude EMG values, it is also 
important to consider functional demands and dosage 
when selecting an exercise for muscle training and 
strengthening, especially in early stages of rehabilita-
tion of a weak or under-recruited muscle. 
The top gluteus medius exercises from Distefano’s 
study were sidelying hip abduction (81%MVIC), sin-
gle-limb squat (64%MVIC), and single limb dead lift 
(58%MVIC).3 With the exception of single limb squat, 
the current study found similar rank order with val-
ues of 63%MVIC, 82%MVIC, and 56%MVIC respec-
tively. Of note, Distefano’s subjects performed the 
single limb squat to a predetermined knee flexion 
angle of approximately 30 degrees,3 while the cur-
rent study had the subjects perform the exercise to a 
predetermined chair height of 47 cm. This differ-
ence in methodology may account for the difference 
in findings across the two studies. The methodology 
used by Distefano may allow for greater normaliza-
tion, as squatting to a predetermined knee flexion 
angle allows for equal challenge to all subjects, 
where as squatting to a predetermined height cre-
ates a greater challenge for taller subjects. 
Bolga’s top exercise for gluteus medius was the pelvic 
drop (57%MVIC).4 The current study found a similar 
value at 58%MVIC, although this exercise was ranked 
11th out of the 22 exercises evaluated. This exercise 
should not be discounted; however, as it is a func-
tional training exercise for pelvic stabilization in sin-
gle limb stance, and many gait abnormalities and 
lower extremity pathologies are the result of the glu-
teus medius muscle’s inability to properly and effec-
tively stabilize the pelvis during single limb stance.
Bolga found sidelying abduction to have a value of 
42%MVIC,4 which is significantly lower than the 
findings in either the Distefano3 or the current study. 
In general, qualitative movement analysis during 
performance of sidelying abduction reveals poor 
technique with frequent substitution using the ten-
sor fascia lata muscle demonstrated through increased 
hip flexion during abduction, which may have 
accounted for the low value found in the Bolga study.6 
Furthermore, subjects in both the Distefano and the 
Bolgla study maintained the bottom leg in neutral 
hip extension and knee extension,3,4 while subjects 
in the current study were allowed to flex the bottom 
hip and knee in order to provide greater support and 
stabilization during abduction of the top leg. 
Ayotte’s top exercise was the unilateral wall squat 
(52%MVIC),5 which is comparable to the single limb 
squat, ranking in the top three exercises in both the 
current study and in Distefano’s study,3 although the 
external stabilization provided in the unilateral wall 
squat should be considered. Ayotte ranked forward 
step-up (44%MVIC) higher than lateral step-up 
(38%MVIC),5 whereas the authors of the current 
study ranked lateral step-up (60%MVIC) higher than 
forward step-up (55%MVIC). It should be noted that 
subjects were allowed upper extremity external sup-
port during the exercise in Ayotte’s study which may 
Table 7. Comparison of rank order of exercises for recruitment of gluteus medius between the current 
study and Distefano,3 Bolgla,4 and Ayotte,5 using %MVIC
*Single-limb wall squat
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 214
account for these differences,5 along with differ-
ences in data analysis described previously. 
Gluteus Maximus
Table 8 depicts the top exercises for gluteus maxi-
mus of the current study. These include front plank 
with hip extension (106%MVIC), gluteal squeeze 
(81%MVIC), side plank abduction with dominant leg 
on top (73%MVIC), side plank abduction with domi-
nant leg on bottom (71%MVIC), and single limb 
squat (71%MVIC). The top four exercises from the 
current study were not performed in other studies. 
Bolgla’s study did not include assessment of perfor-
mance of the gluteus maximus so will not be included 
in the discussion below.4
Distefano’s top exercises were single limb squat 
(59%MVIC), single limb dead lift (59%MVIC), and 
sidelying hip abduction (39%MVIC).3 Subjects per-
forming these same exercises in the current study pro-
duced results of 71%MVIC, 59%MVIC, and 51%MVIC, 
respectively, demonstrating the same rank order of 
muscle activity as these exercises in the Distefano 
study.3 The only differences in rank ordering between 
the current study and Distefano’s for gluteus maximus 
were between clamshell progression 1 and sidelying 
abduction;3 however, within each study there was less 
than 5%MVIC difference for each exercise when deter-
mining rank order (Table 8). As previously noted, dif-
ferences in technique and substitution are common 
occurrences during the performance of sidelying abduc-
tion which may account for the differences found 
between the two studies.
Ayotte ranked forward step-up (74%MVIC) higher 
than lateral step-up (56%MVIC),5 whereas the current 
study ranked lateral step-up (64%MVIC) higher than 
forward step-up (55%MVIC). Again, differences could 
be attributed to variances in technique or the ability of 
subjects in Ayotte’s study to use external upper extrem-
ity support5 as well as differences in data analysis. 
The low ranking for stable single limb bridge (11th) 
and unstable single limb bridge (14th) was somewhat 
surprising as both are common exercises used clini-
cally for gluteus maximus strengthening. There 
were several instances of subjects reporting ham-
string cramping during bridging on the unstable sur-
face, which led the researchers to suspect substitution 
with the hamstrings during this exercise. The same 
may holdtrue for bridging on the stable surface, 
however there were fewer complaints. Future stud-
ies should examine muscle recruitment and activa-
tion patterns of gluteus maximus and the hamstrings 
during various bridging activities. 
The effect of a subject’s attention to volitional con-
traction of a muscle during an exercise should also 
be considered. The gluteal squeeze was the only 
exercise where verbal cues were explicitly given to 
maximally contract the gluteal muscles while per-
forming the exercise, which could possibly have 
contributed to its high ranking for performance by 
the gluteus maximus. Future research should exam-
ine the difference in amount, if any, noted in mus-
cle recruitment when verbal instructions are given 
to concentrate on the muscle contraction while 
Table 8. Comparison of rank order of exercises for recruitment of gluteus maximus between the 
current study and Distefano,3 and Ayotte,5 using %MVIC.
*Single-limb squat
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 215
performing the exercise versus no verbal instruc-
tions during performance. The effects of tone of 
voice, volume of cues, and frequency of verbal cue-
ing are unknown.
CONCLUSION
Anderson and Fry have previously reported that 
higher %MVIC values with exercises correlate to 
muscle hypertrophy.20,22 By knowing the %MVIC of 
the gluteus maximus and medius that occurs during 
various exercises, the potential for strengthening 
these muscles can be inferred. Subsequently, exer-
cises may be ranked to appropriately challenge the 
gluteus maximus and medius during rehabilitation. 
The authors of the current study found patterns 
within their results consistent with previous research 
published by Distefano and Bolgla.3,4 The authors 
conclude that differences in data collection and 
analysis as well as the use of external upper extrem-
ity support may have accounted for the differences 
noted between the current study and the study by 
Ayotte.5 One of the purposes of the current study 
was to provide a rank ordered list of exercises for the 
recruitment of the gluteus maximus and medius. 
These rank ordered lists may help form the basis for 
a graded rehabilitation program. For patients early 
in the rehabilitation process, the clinician should 
systematically determine which muscle they are 
wishing to strengthen and use less difficult (lower 
%MVIC) exercises. In order to maximally challenge 
a patient’s gluteus maximus and medius, the authors 
recommend using a front plank with hip extension, 
a single limb squat, and a side plank on either 
extremity with hip abduction. 
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Muscle Fibre Adaptations. Sports Med. 2004; 34: 
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Activation with The Twitch Interpolation Technique. 
Sports Med. 2004; 34: 253-267.
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 217
APPENDIX A
1. Clamshell (hip clam) Progression: Each 
exercise is performed with the subject sidelying on 
the non-dominant side. (Figure 3) 
a. Progression 1 (upper left): Start position is 
sidelying with hips flexed to approximately 45 
degrees, knees flexed, and feettogether. Subject 
externally rotates the top hip to bring the knees 
apart for one metronome beat and returns to 
start position during the next beat.
b. Progression 2 (upper right): Start position iden-
tical to progression 1; however, in this progression 
subject keeps the knees together while internally 
rotating the top hip to lift the top foot away from 
the bottom foot for one metronome beat, return-
ing to the start position during the next beat 
c. Progression 3 (lower left): The subject is posi-
tioned identical to progressions 1 and 2, but with 
the top leg raised parallel to the ground. The sub-
ject maintains the height of the knee while inter-
nally rotating at the hip by bringing the foot 
toward the ceiling for one beat and then returns 
to the start position during the next beat. 
d. Progression 4 (lower right): The subject is 
positioned the same as progression 3, but with 
the hip fully extended. As in progression 3, the 
subject maintains the height of the knee and 
internally rotates at the hip by bringing the foot 
toward the ceiling for one beat and returns to 
the start position with knee and ankle in line 
during the next beat. 
2. Pelvic drop: Subject stands with dominant leg on 
the edge of a 5 cm box (right), and then lowers the 
heel of the non-dominant leg to touch the ground 
without bearing weight, for one beat (left). Subject 
returns foot to the height of the box while keeping 
the hips and knees extended for one beat. (Figure 4)
Figure 3. 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 218
3. Sidelying abduction: Start with subject sidely-
ing on non-dominant side. Subject flexes the hip and 
knee of the support side and then abducts the domi-
nant leg to approximately 30 degrees while main-
taining neutral or slight hip extension and knee 
extension with the toes pointed forward for a count 
of two beats up and two beats down. (Figure 5) 
4. Side Plank with Abduction, dominant leg up: 
(Start with subject in a side plank position with domi-
nant leg up. Subject is instructed to keep shoulders, 
hips, knees, and ankles in line bilaterally, and then to 
rise to plank position with hips lifted off ground to 
achieve neutral alignment of trunk, hips, and knees. 
The subject is allowed upper extremity support as seen Figure 5. 
Figure 6. 
Figure 4. 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 219
Figure 8. 
on left. While balancing on elbows and feet, the subject 
raises the top leg into abduction (right) for one beat 
and then lowers leg for one beat. Subject maintains 
plank position throughout all repetitions (Figure 6). 
5. Side Plank with Abduction, dominant leg down: 
Exercise position is identical to Exercise 4 except on the 
opposite side. Subject is instructed to abduct the non-
dominant uppermost leg for two beats and lowers leg 
for two beats. Subject maintains plank position through-
out all repetitions. 
6. Front Plank with Hip Extension: Start with sub-
ject prone on elbows in plank with trunk, hips, and 
knees in neutral alignment (left). Subject lifts the 
dominant leg off of the ground, flexes the knee of the 
dominant leg, and extends the hip past neutral hip 
alignment by bringing the heel toward the ceiling 
(right) for one beat and then returns to parallel for 
one beat. (Figure 7)
7. Single Limb Bridging on Stable Surface: Start 
with subject in hook-lying position (left). The sub-
ject is instructed to bridge on both legs by keeping 
the feet on the floor and raising hips off the ground 
to achieve neutral trunk, hip, and knee alignment 
for one beat. From this position, the subject extends 
the knee of the non-dominant leg to full knee exten-
sion while keeping the femurs parallel (right) for 
one beat, returns the non-dominant leg to the bridge 
position for one beat, and then lowers the body back 
to the ground for one beat (Figure 8). 
8. Single Limb Bridge on Unstable Surface: Sub-
ject is positioned as in Exercise 7 and places the 
dominant foot in the center of the Core-Tex™ (left). 
Figure 7. 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 220
Figure 10. 
The subject performs the same sequence as above 
(right) while maintaining the disc of the Core-Tex™ 
in the center. (Figure 9)
9. Hip Circumduction on Stable Surface: The sub-
ject places the non-dominant leg on the outside of the 
base of the Core-Tex™ and stands to the side of the 
Core-Tex™ on the dominant leg (left). The subject per-
forms a single limb squat while tracing the toe of the 
non-dominant leg on the outside of the Core-Tex™ base 
(right) in an arc for three beats, then traces the toe 
back to the start, while returning to a standing position 
Figure 9. 
for three beats. Subjects were allowed two-finger uni-
lateral upper extremity support on the frame of the 
Core-Tex™ for balance assist. (Figure 10).
10. Hip Circumduction on Unstable Surface: In 
standing, the subject places the non-dominant foot on 
the outer edge of the Core-Tex™ and stands to the side 
of the Core-Tex™ on the dominant leg (left). The sub-
ject then performs a single limb squat on the domi-
nant leg while drawing an arc with the non-dominant 
foot, extending the arc away from the subject for three 
beats (right). The subject then returns the foot to the 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 221
Figure 12. Figure 13. 
Figure 11. 
starting position by drawing the foot in, while return-
ing to a standing position for three beats. Subjects 
were allowed upper extremity support as in Exercise 9. 
(Figure 11) 
11. Single Limb Squat: Subject stands on the domi-
nant leg, slowly lowering the buttocks to touch a 
chair 47cm in height for two beats and then extends 
back to standing for two beats. (Figure 12) 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 222
Figure 14. 
Figure 15. 
12. Single Limb Deadlift: Subject stands on the 
dominant leg and slowly flexes at the hip, keeping 
the back straight, to touch the floor with the oppo-
site hand for two beats. Subject then extends at the 
hip to standing for two beats. Subjects were permit-
ted to have knees either straight or slightly bent in 
the case that hamstring tightness limited subject’s 
ability to touch the floor. (Figure 13) 
13. Dynamic Leg Swing: Subject is positioned in stand-
ing on the dominant leg, and then begins to swing the 
non-dominant leg (with the knee flexed) into hip flexion 
(left) and extension (right) at a rate of one beat forward 
and one beat backward. Subjects were instructed to 
move through a smooth range of hip motion and to not 
allow their trunk to move out of the upright position. 
(Figure 14)
14. Forward Step-up: Beginning with both feet on the 
ground, subject steps forward onto a 20cm step with 
the dominant leg for one beat. Subject then steps up 
with the non-dominant leg during the next beat. Sub-
ject then lowers the non-dominant leg back to the 
ground for one beat followed by the dominant leg dur-
ing the next beat. (Figure 15)
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 223
Figure 18. 
Figure 16. 
Figure 17. 
15. Lateral Step-up: Subject stands on the edge of a 
15cm box on the dominant leg and squats slowly to 
lower the heel of the non-dominant leg toward floor 
for one beat and then returns to start position during 
the next beat. (Figure 16) 
16. Quadruped Hip Extension: In quadruped (left) 
the subject extends the dominant leg at the hip, while 
keeping the knee flexed 90 degrees, to lift the foot 
toward the ceiling (right) to achieve neutral hip exten-
sion for two beats and then returns the dominant leg 
to the start position for two beats. This exercise was 
repeated with the non-dominant leg and EMG values 
were recorded in orderto measure activity as both 
the stabilizing and moving leg. (Figure 17)
17. Skater Squat: Subject stands on the dominant 
leg and performs a squat to a comfortable knee flex-
ion angle for two beats down and two beats up with 
non-dominant leg extended at the hip and flexed at 
the knee. The torso twists during the squat. The toe 
of the non-dominant leg was permitted to touch the 
ground between repetitions. (Figure 18)
18. Gluteal Squeeze: In standing with feet shoul-
der-width apart, subject squeezes gluteal muscles 
for two beats and then relaxes for two beats. Subjects 
were instructed to maximally contract the gluteal 
musculature during the exercise.
ARTIGO ORIGINAL
ISSN: 2178-7514
Vol. 7 | Nº. 1| Ano 2015
AVALIAÇÃO INDIRETA DA FORÇA DOS MÚSCULOS DO CORE 
EM INICIANTES DE ACADEMIA
Evaluation of core muscles strength in beginners of the resistance training
Marcia Aurora Soriano Reis1, Mauro Antonio Guiselini2; Priscyla Silva Monteiro Nardi3, 
Guanis de Barros Vilela Junior1; Paulo Henrique Marchetti1,2,3
RESUMO
O objetivo deste estudo foi avaliar e classificar o nível de força de forma indireta os músculos do 
core em indivíduos ingressantes de academia baseados na proposta de avaliação de Kendall. A 
amostra foi composta por 1317 alunos ingressantes de uma academia de ginástica de São Paulo, 
submetidos a uma bateria de testes de avaliação física, sendo 536 do sexo masculino e 781 do sexo 
feminino, agrupados por faixas etárias entre 20 a 29 anos, 30 a 39 anos, 40 a 49 anos e 50 a 59 anos. 
Foram realizadas análises de percentual, onde o grupo total de sujeitos foi separado em diferentes 
amostras como gênero e idade, e comparados em relação ao percentual total dos escores obtidos no 
teste. Conclui-se que a grande maioria dos indivíduos não apresenta um grau adequado de força e 
estabilidade do core baseados na proposta de avaliação de Kendall. 
Palavras-chave: biomecânica, treinamento, desempenho.
ABSTRACT
The objective of this study was to evaluate and classify indirectly the level of core muscle strength 
in beginners in a academy based on Kendall’s assessment test. The sample consisted of 1317 (536 
male and 781 female) beginners in a fitness facility of Sâo Paulo, submitted to Kendall’s assessment 
test, grouped by age (20 to 29 years, 30 to 39, 40-49 years, and 50-59 years) and gender. Analysis of 
percentage were performed , and compared to the total percentage of the scores obtained in the test. 
It was concluded that the vast majority of people did not present an adequate degree of strength and 
core stability based on the Kendall’s evaluation.
Keywords: biomechanics, training, performance.
Autor de correspondência: 
Paulo H. Marchetti
Universidade Metodista de Piracicaba 
Rodovia do Açúcar Km 156, Bloco 7, Sala 39, Taquaral 
13423-070 - Piracicaba, SP – Brasil 
E-mail: pmarchetti@unimep.br
1Grupo de Pesquisa em Performance Humana, Programa de Pós-
Graduação Stricto Sensu em Ciências do Movimento Humano, Faculdade 
de Ciências da Saúde (FACIS), UNIMEP, Piracicaba, SP, Brasil; 
2Faculdades de Educação Física da FMU, São Paulo, Brasil; 
3Instituto de Ortopedia e Traumatologia, Faculdade de Medicina, Universidade de São Paulo, 
São Paulo, Brasil.
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 2
1. INTRODUÇÃO
Uma prescrição de treinamento adequada 
é uma das responsabilidades primordiais de 
instrutores e treinadores em academias, e está 
relacionada à escolha dos exercícios e variáveis 
de carga, considerando principalmente o nível 
atual de condicionamento físico do cliente 
(MARCHETTI e LOPES, 2014)1. Dentre as 
diversas atividades de academia, a chamada 
musculatura do core acaba sendo empregada 
na maioria das vezes como objetivo de 
estabilização, equilíbrio e transferência de 
forças entre segmentos (aumento da rigidez 
estrutural). De acordo com Behm et al. 
(BEHM, DRINKWATER, WILLARDSON e 
COWLEY, 2010)2 o conceito anatômico de core 
baseia-se no esqueleto axial (cintura pélvica 
e escapular), os tecidos moles (articulações, 
fibro-cartilagem, ligamentos, tendões, fáscias e 
músculos) se originando no próprio esqueleto 
axial (os quais podem possuir inserções axiais 
ou apendiculares como os segmentos).
 Estudos indicam que a força e 
potência podem ser afetadas por uma limitada 
capacidade de rigidez/estabilidade do core, 
influenciando a transferência de forças entre 
segmentos. A estabilidade/rigidez do core pode 
ser representada pela interação de 3 subsistemas 
(neural, passivo e ativo), os quais deveriam ser 
considerados principalmente em programas 
de treinamento onde os níveis de força do 
mesmo são baixos (BEHM, DRINKWATER, 
WILLARDSON e COWLEY, 20103; BEHM 
e SANCHEZ, 20124; 20134). Desta forma, 
clientes que apresentam baixo nível de força do 
core podem apresentar dificuldades em outras 
atividades de academia como musculação, 
natação, ginástica, treinamento funcional entre 
outras. Portanto, uma prévia avaliação do core 
pode ser considerada uma ferramenta útil para 
a implementação de exercícios específicos e/
ou complementares ao programa regular na 
academia. 
O objetivo deste estudo foi avaliar 
e classificar o nível de força de forma 
indireta os músculos do core em indivíduos 
ingressantes de academia baseados na proposta 
de avaliação de Kendall et al., (1993)5. 
 
2. MATERIAIS E MÉTODOS 
2.1.Participantes
 A amostra foi composta por 1317 alunos 
ingressantes de uma academia de ginástica de 
São Paulo, submetidos a uma bateria de testes de 
avaliação física, sendo 536 do sexo masculino 
e 781 do sexo feminino, agrupados por faixas 
etárias entre 20 a 29 anos, 30 a 39 anos, 40 a 
49 anos e 50 a 59 anos. Os critérios de inclusão 
adotados foram os seguintes: 1) sem quaisquer 
cirurgias, lesões ou qualquer acometimento 
músculo-esquelético em membros inferiores 
(menos de 1 ano); 2) não terem treinado os 
membros inferiores nas 48 horas antecedentes 
ao protocolo experimental; 3) não apresentarem 
desordens neurológicas periféricas e/ou 
centrais; 4) serem capazes de realizar os testes 
propostos. Todos os sujeitos foram informados 
dos procedimentos experimentais e assinaram
Avaliação indireta da força dos músculos do core em iniciantes de academia
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o termo de consentimento livre e esclarecido, 
aprovado pelo Comitê de Ética em Pesquisa da 
Universidade. 
2.2.Procedimentos
 Os sujeitos se apresentaram apenas 
uma vez ao laboratório onde foi realizado um 
teste de abaixamento dos membros inferiores 
baseado no teste de Kendall (KENDALL, MC-
CREARY e PROVANCE, 1993)5, partindo da 
posição inicial em decúbito dorsal, membros 
inferiores na vertical estabelecendo um ângulo 
de 90° com o solo; com o objetivo de graduar 
a força dos músculos abdominais e flexores de 
quadril (Figura 1). O sujeito recebeu instruções 
do avaliador, como segue: Posição inicial em 
decúbito dorsal, antebraços flexionados sobre 
o tórax, elevação de um membro inferior por 
vez, até a posição vertical e manutenção dos 
joelhos estendidos. Inclinação posterior da 
pelve, retificando a coluna lombar sobre o solo 
e manutenção desta posição durante o teste. 
Cabeça e ombros devem permanecer encosta-
dos no solo. A execução do teste consistiu em 
o indivíduo abaixar lenta e simultaneamente os 
membros inferiores, mantendo a pelve em in-
clinação posterior.
FIGURA 1. Teste de abaixamento de membros inferiores: (a) início da avaliação; (b) máxima amplitude atingida 
(KENDALL, MCCREARY e PROVANCE, 1993).
A força foi graduada baseando-se na 
capacidade de manter a região lombar 
retificada sobre a superfície durante o 
abaixamento lento de ambos os membros 
inferiores. A força de contração excêntrica 
exercida pelos músculos flexoresdo quadril 
e pelo abaixamento dos membros inferiores 
tende a inclinar a pelve anteriormente, atuando 
como uma forte resistência contra os músculos 
abdominais, que estão tentando manter a 
pelve em inclinação posterior. No momento 
em que a pelve se inclina anteriormente e a 
região lombar se arqueia ,caracteriza-se a 
instabilidade, e o teste é interrompido. 
Avaliação indireta da força dos músculos do core em iniciantes de academia
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A força dos músculos abdominais é graduada 
através do ângulo formado entre os membros 
inferiores estendidos e o solo. Para a determi-
nação do ângulo em graus, foi utilizado um 
flexímetro (Sanny, Sanny do Brasil) posiciona-
do no tornozelo esquerdo do avaliado. O teste 
foi sempre realizado na mesma hora do dia e 
pelo mesmo avaliador. 
2.3. Análise dos Dados
 A escala para a graduação da força 
muscular utilizada e o código para tal gradu-
ação seguem a referência de Kendall (KEND-
ALL, MCCREARY e PROVANCE, 1993)5, a 
qual retrata cada possível ângulo em grau e seu 
correspondente índice qualitativo (Figura 2) e a 
tabela 1 mostra o código para a graduação mus-
cular.
Figura 2. Escala de graduação ângulo/ìndice.
Função do músculo Graus musculares e símbolos
Mantém a posição do teste (sem acrescentar pressão). Regular 5
Mantém a posição do teste contra uma pressão discreta. Regular + 6
Mantém a posição de teste contra uma pressão discreta a moderada. Bom - 7
Mantém a posição de teste contra uma pressão moderada. Bom 8
Mantém a posição de teste contra uma pressão moderada a forte. Bom + 9
Mantém a posição de teste contra uma pressão forte Normal 10
Tabela 1. Código para a graduação muscular.
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2.4. Análise Estatística
 Foram realizadas análises de percentu-
al, onde o grupo total de sujeitos foi separado 
em diferentes amostras como gênero e idade, e 
comparados em relação ao percentual total dos 
escores obtidos no teste. 
3. RESULTADOS
 Considerando o grupo total de sujeitos 
da amostra (n=1317), observou-se que apenas 
2,15% apresentaram classificações entre “Bom 
+” e “Normal”, 
sendo que 68,8% ficaram entre as classificações 
“Regular +” e “Bom -” (Tabela 2). 
Tabela 2 - Classificação geral do nível de força 
do core
Graduação n %
Regular - 269 15,8
Regular + 611 35,9
Bom - 525 30,9
Bom 265 15,6
Bom + 20 1,2
Normal 11 0,6
 Separando a amostra quanto ao gênero 
observou-se que os homens (n=536) apresenta-
ram 2,4% e as mulheres (n=781) apenas 1,8% 
nas classificações “Bom +” e “Normal”, sendo 
que a maior parte deles encontrou-se nas cate-
gorias “Regular +” e “Bom-” (homens= 64,4% 
e mulheres=68,8%) (Tabela 3).
Tabela 3- Classificação por gênero do nível de 
força do core.
Graduação Homens Mulheres
n % n %
Regular - 73 10,3 196 19,8
Regular + 220 31,0 391 39,5
Bom - 237 33,4 288 29,1
Bom 163 23,0 102 10,3
Bom + 10 1,4 10 1,0
Normal 7 1,0 4 0,4
 Separando a amostra de forma geral, 
quanto a faixa etária, observou-se que dos 1317 
indivíduos, uma pequena porcentagem encon-
trou-se entre “Bom +” e “Normal”, sendo que 
a maioria se concentraram entre “Regular +” e 
“Bom -” (Tabela 4).
Graduação
20-29 anos 30-39 anos 40-49 anos 50-59 anos
n % n % n % n %
Regular - 59 13,5 49 11,3 33 10,7 20 14,8
Regular + 160 36,6 172 39,5 98 31,9 43 31,9
Bom - 137 31,4 135 31,0 121 39,4 40 29,6
Bom 74 16,9 74 17,0 48 15,6 27 20,0
Bom + 5 1,1 5 1,1 5 1,6 3 2,2
Normal 2 0,5 3 0,7 2 0,7 2 1,5
Tabela 4. Classificação geral por faixa etária do nível de força do core
Avaliação indireta da força dos músculos do core em iniciantes de academia
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Separando a amostra quanto a faixa etária e 
gênero, observou-se que os homens (n=536), 
apresentaram uma baixa porcentagem entre 
“Bom +” e “Normal”, porém, para as idades 
entre 40 e 49 anos, assim como para as idades 
entre 50 e 59 anos, não foram observados in-
divíduos na classificação “Normal”. Para todas 
as faixas etárias, aproximadamente 25% dos 
indivíduos homens encontraram-se na classifi-
cação “Bom” (Tabela 5).
Graduação
20-29 anos 30-39 anos 40-49 anos 50-59 anos
n % n % n % n %
Regular - 10 5,0 9 5,5 6 5,3 5 8,6
Regular + 65 32,5 51 31,1 31 27,2 20 34,5
Bom - 70 35 55 33,5 49 43 16 27,6
Bom 50 25 43 26,2 27 23,7 16 27,6
Bom + 3 1,5 3 1,8 1 0,9 1 1,7
Normal 2 1,0 3 1,8 0 0,0 0 0,0
Separando a amostra de mulheres (n=781), 
quanto a faixa etária, apresentaram uma 
pequena porcentagem entre “Bom +” e 
“Normal”, para as idades entre 20 e 29 anos, 
assim como para as idades entre 30 e 39 anos, 
entretanto, não foram observados indivíduos 
na classificação “Normal” (Tabela 6).
Tabela 5. Classificação dos homens por faixa etária do nível de força do core
Graduação
20-29 anos 30-39 anos 40-49 anos 50-59 anos
n % n % n % n %
Regular - 49 20,7 40 14,6 27 14,0 15 19,5
Regular + 95 40,1 121 44,2 67 34,7 23 29,9
Bom - 67 28,3 80 29,2 72 37,3 24 31,2
Bom 24 10,1 31 11,3 21 10,9 11 14,3
Bom + 2 0,8 2 0,7 4 2,1 2 2,6
Normal 0 0,0 0 0,0 2 1,0 2 2,6
Tabela 6. Classificação das mulheres por faixa etária do nível de força do core
4. DISCUSSÃO
Conhecimentos cinesiológicos e biomecânicos 
sobre o core tem se consolidado cada vez tanto 
em relação ao treinamento e à reabilitação. As 
dores lombares têm sido relacionadas com o 
atraso na ativação do transverso do abdome, 
atrofia dos multifidos, fraqueza dos músculos 
extensores, déficit na propriocepção espinhal, 
equilíbrio e resposta à perturbações (BARR ET 
AL., 20076; GARRY ET AL., 20087; HIDES 
ET AL., 19968; HODGES & RICHARDSON, 
19969; KIBLER, 200610). Assim, a estabilidade 
do core como prevenção de lesões na região 
lombar e em outras regiões do corpo e o 
treinamento desta musculatura têm sido 
recomendados como promoção de um regime 
preventivo e terapêutico (AKUTHOTA & 
NADLER, 200411; WILLSON ET AL., 200512). 
Vilela Junior, Hauser, et al (201113) ressaltam 
que a estabilidade anterior da coluna vertebral
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é realizada pelos músculos reto do abdome, oblíquos 
interno e externo, cujas forças resultantes, em con-
dições ideais, devem formar entre si ângulos retos 
com ortogonalidade espacial; ao passo que a esta-
bilidade posterior da coluna vertebral é realizada 
pelos músculos eretores da espinha, interespinhais, 
intertransversais, quadrado lombar e serrátil poste-
rior. Então, cabe ao professor/ treinador prescrever 
exercícios para o fortalecimento destes complexos 
musculares.
 Reinehr et al. (200814) estudaram como um 
programa de exercícios para a estabilização do core 
influencia a estabilidade e a ocorrência de dor lom-
bar, e verificaram que após o treinamento houve 
diminuição da dor lombar e aumento da força ab-
dominal e estabilidade do core. Este artigo corrob-
orou os resultados do presente estudo, pois foi apli-
cado o mesmo teste de abaixamento dos membros 
inferiores. Verificaram que os indivíduos portadores 
de dores lombares crônicas, no pré-treinamento es-
tavam situados na classificação para o nível de força 
do core nos graus 0,1 e 2; o que correspondeu neste 
estudo aos graus 5, 6 e 7 que significam respectiva-
mente a Regular, Regular + e Bom -. No pós-trein-
amento estes indivíduos obtiveram ganho de força 
e estabilidade do core, alcançando graus 4 e 5, cor-
respondentes neste estudo aos graus 9 e 10, que sig-
nificam respectivamente a Bom + e Normal. Os au-
tores concluíram que os ganhos de força abdominal 
indicaram que este tipo de programa de treinamento 
para o core foiefetivo para o aumento da força e 
estabilidade core e diminuição da lombalgia. 
Neste presente estudo, os indivíduos ingressantes na 
academia de ginástica que foram avaliados no teste 
de abaixamento dos membros inferiores, em sua 
maioria, foram classificados para o nível de força 
do core nos graus 5, 6 e 7 significando, respectiva-
mente, Regular, Regular + e Bom -. 
 De acordo com o código para a graduação 
muscular, as funções dos músculos para as classi-
ficações acima, representam um estado de pouca 
força e estabilidade do core, já que os mesmos não 
suportaram a posição do teste contra pressões acima 
de moderadas. Para a classificação 8 (Bom), onde 
se mantem a posição do teste contra uma pressão 
moderada, apenas 16,9% dos indivíduos avali-
ados conseguiram este grau. Quando separados por 
gênero, os homens atingiram 25,4% e as mulheres 
apenas 11,1%. No código para graduação muscular, 
os graus 9 e 10 (Bom + e Normal), significam que o 
indivíduo consegue manter a posição do teste contra 
pressões moderada a forte e forte respectivamente. 
Dos avaliados neste estudo, apenas 2,1% obtiveram 
as classificações Bom + e Normal. Quando a 
classificação foi separada por faixa etária e gênero, 
observou-se que, para todas as idades, a grande 
porcentagem dos indivíduos ficou entre as classifi-
cações Regular-, Regular + e Bom -. Os homens de 
40 a 49 anos e 50 a 59 anos, não conseguiram a 
classificação Normal, sendo que as mulheres que 
não atingiram essa classificação foram as de 20 a 29 
anos e 30 a 39 anos. 
 A partir dos resultados encontrados neste 
estudo, observa-se que a grande maioria dos indi-
víduos não apresentou um grau adequado de força e 
estabilidade do core.
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 8
Tal fato, muito provavelmente, é consequên-
cia do enfraquecimento dos músculos que es-
tabilizam anterior e posteriormente a coluna 
vertebral e do desequilíbrio entre as forças 
resultantes exercidas sobre a pélvis que sofre 
um torque resultante no sentido anterior, espe-
cialmente fruto do enfraquecimento do reto do 
abdome e consequente inclinação anterior da 
coluna lombar acentuando a lordose da mesma 
(VILELA JUNIOR, HAUSER, 201113). Neste 
sentido, fica patente que um core em condições 
biomecânicas ideais, depende do fortaleci-
mento harmônico dos eretores da espinha, dos 
extensores do quadril, dos flexores do quadril 
e dos abdominais, uma vez que o enfraqueci-
mento de um destes complexos musculares 
acarretará a rotação da pélvis e consequente-
mente a inclinação posterior ou anterior da 
coluna. O instrumento utilizado neste estudo, 
apesar de simples, avalia em última instância, 
o quanto o sujeito consegue estabilizar a pélvis.
 Akuthota et al., (200411) sugeriram que 
pessoas sedentárias, com enfraquecimento da 
musculatura estabilizadora, deveriam inicial-
mente ser submetidas a um programa de exercí-
cios para o fortalecimento do core, ao invés de 
realizarem os tradicionais exercícios abdomi-
nais (seat-ups), já que a realização destes, sem 
o devido fortalecimento do core, implica em 
lesões ou dores lombares. Juker et al. (198815) 
afirmaram que os seat-ups não são seguros 
devido a acentuada carga de compressão dos 
discos vertebrais. 
 Como as academias de ginástica pos-
suem diversos programas de exercícios e a aval-
iação física fornece subsídios para prescrevê-
los, seria interessante que fossem detectadas 
as reais condições de força e estabilidade do 
core dos alunos ingressantes para que as pre-
scrições fossem adequadas às necessidades dos 
mesmos. Entretanto, Pavin e Gonçalves (2010) 
abordaram a discussão sobre as controvérsias 
no uso de programas de exercícios para o core 
e as lombalgias (BERGMARK,1989; FARIES, 
& GREENWOOD, 200718; PANJABI, 199219; 
WILLARDSON, 200720). 
 Considera-se como uma das princi-
pais limitações do presente estudo a utilização 
do teste de um teste básico e genérico para a 
avaliação do core, sendo que o mesmo não 
abrange toda as estruturas necessárias para a 
avaliação. Entretanto, pode ser um teste adi-
cional ao programa de avaliação física de aca-
demia como teste adicional para auxiliar os 
instrutores quanto à potencial fragilidade do 
cliente. 
5. CONCLUSÃO
Conclui-se que a grande maioria dos indivídu-
os não apresenta um grau adequado de força e 
estabilidade do core baseados na proposta de 
avaliação de Kendall. 
 
6. REFERÊNCIAS
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 9
1. Marchetti, P. H.& Lopes, C. R. (2014) Plane-
jamento e Prescrição do Treinamento Personali-
zado: do iniciante ao avançado. São Paulo: Mundo. 
2.Behm, D. G., Drinkwater, E. J., Willardson, J. 
M.& Cowley, P. M. (2010) The use of instability 
to train the core musculature. Applied Physiology, 
Nutrition and Metabolism, v. 35, p. 91-108. 
3. Behm, D. G. & Sanchez, J. C. C. (2013) Instabil-
ity Resistance Training Across the Exercise Contin-
uum. Sports Health: A Multidisciplinary Approach, 
p. 1-5.
4. Behm, D. G.& Sanchez, J. C. C. (2012) The ef-
fectiveness of resistance training using unstable 
surfaces and devices for rehabilitation. The Inter-
national Journal of Sports Physical Therapy, v. 7, n. 
2, p. 226-241.
5. Kendall, F. P., McCreary, E. K. & Provance, P. G. 
(1993) Muscles: Testing and Function. 4. Philadel-
phia: Williams and Wilkens. 
6. Barr, K.P., Griggs, M. & Cadby, P. (2007). Lum-
bar stabilization: a review of core concepts and cur-
rent literature, part 2. American Journal of Physical 
Medicine and Rehabilitation, 86 (6), 72-80.
7. Garry, T. A., Sue, L. M. & Brendan, L. (2008). 
Feedforward responses of tranverses abdominis 
are directionally specific and act asymmetrically: 
implications for core stability theories. Journal of 
Orthopardic and Sports Physical Theraphy, 38 (5), 
228-37. 
8. Hides, J. A., Richardson, C. A. & Jull, J. A. 
(1996). Multifidus muscle recovery is not automat-
ic after resolution of acute, first-episode low back 
pain. Spine, 21, 2763-9.
9. Hodges, P. W. & Richardson, C. A. (1996). In-
efficient muscular stabilization of the lumbar spine 
associated with low back pain: A motor control 
evaluation of transversus abdominis. Spine, 21, 
2640-2650.
10. Kibler, W. B., Press, J. & Sciascia, A. (2006). 
The hole of core stability in athletic function. Sports 
Medicine, 36 (3), 189-98.
11. Akuthota, V. & Nadler, S.F. (2004). Core 
strengthening. Archives of Physical Medicine and 
Rehabilitation.,85(3 Suppl 1),86-92.
12. Willson, J. D., Dougherty, C. P., Ireland, M. 
L. & Davis, I. M. (2005). Core stability and its re-
lationship to lower extremity function and injury. 
Journal of American Academy of Orthopaedic Sur-
gery, 13 (5), 316-25.
13. Vilela Junior, G. B. Hauser, M.W. et al (2011). 
Cinesiologia. Ponta Grossa, PR: Editora UEPG, 71- 
75.
14. Reinehr. F.B, Carpes F.P, Bolli M.C. (2008) 
Influência do treinamento de estabilização central 
sobre a dor e estabilidade lombar. Fisioterapia em 
movimento, 1,123-129.
15. Juker, D., McGill, S., Kropf, P. & Steffen, T. 
(1998). Quantitative intramuscular myoelectric ac-
tivity of lumbar portions of psoas and the abdomi-
nal wall during a wide variety of tasks. Medicine 
Science and Sports Exercise, 30, 301-310. 
16. Pavin, L. N. & Gonçalves, C. (2010). Principles 
of core stability in the training and in the rehabili-
tation: review of literature. Journal of Health and 
Scince Institute, 28 (1), 56-8.
17. Bergmark, A. (1989). Stability of the lumbar 
spine. A study in mechanical engineering. Acta Or-
thopaedica Scandinavica, 230, 1-54.
18. Faries, M. D. & Greenwood, M. (2007). Core 
training: stabilizing the confusion. Strength and 
Conditioning Journal, 29 (2), 10-25.
19. Panjabi,M. M. (1992). The stabilizing system 
of the spine. Part II. Neutral zone and instability hy-
pothesis. Journal of Spinal Disorders, 5, 390-397. 
20. Willardson, J. M. (2007). Core stability train-
ing: applications to sports conditioning programs. 
Journal of Strength and Conditioning Research, 
21(3), 979 – 985. 
FOCUSED REVIEW
Core Strengthening
Venu Akuthota, MD, Scott F. Nadler, DO
ABSTRACT. Akuthota V, Nadler SF. Core strengthening.
Arch Phys Med Rehabil 2004;85(3 Suppl 1):S86-92.
Core strengthening has become a major trend in rehabilita-
tion. The term has been used to connote lumbar stabilization,
motor control training, and other regimens. Core strengthening
is, in essence, a description of the muscular control required
around the lumbar spine to maintain functional stability. De-
spite its widespread use, core strengthening has had meager
research. Core strengthening has been promoted as a preven-
tive regimen, as a form of rehabilitation, and as a performance-
enhancing program for various lumbar spine and musculoskel-
etal injuries. The intent of this review is to describe the
available literature on core strengthening using a theoretical
framework.
Overall Article Objective: To understand the concept of
core strengthening.
Key Words: Athletic injuries; Exercise; Low back pain;
Rehabilitation.
© 2004 by the American Academy of Physical Medicine and
Rehabilitation
CORE STRENGTHENING HAS BEEN rediscovered in
rehabilitation. The term has come to connote lumbar sta-
bilization and other therapeutic exercise regimens (table 1). In
essence, all terms describe the muscular control required
around the lumbar spine to maintain functional stability. The
“core” has been described as a box with the abdominals in the
front, paraspinals and gluteals in the back, the diaphragm as the
roof, and the pelvic floor and hip girdle musculature as the
bottom.1 Particular attention has been paid to the core because
it serves as a muscular corset that works as a unit to stabilize
the body and spine, with and without limb movement. In short,
the core serves as the center of the functional kinetic chain. In
the alternative medicine world, the core has been referred to as
the “powerhouse,” the foundation or engine of all limb move-
ment. A comprehensive strengthening or facilitation of these
core muscles has been advocated as a way to prevent and
rehabilitate various lumbar spine and musculoskeletal disorders
and as a way to enhance athletic performance. Despite its
widespread use, research in core strengthening is meager. The
present review was undertaken to describe the available liter-
ature using a theoretical framework.
Stability of the lumbar spine requires both passive stiffness,
through the osseous and ligamentous structures, and active
stiffness, through muscles. A bare spine, without muscles at-
tached, is unable to bear much of a compressive load.2,3 Spinal
instability occurs when either of these components is disturbed.
Gross instability is true displacement of vertebrae, such as with
traumatic disruption of 2 of 3 vertebral columns. On the other
hand, functional instability is defined as a relative increase in
the range of the neutral zone (the range in which internal
resistance from active muscular control is minimal).4 Active
stiffness or stability can be achieved through muscular cocon-
traction, akin to tightening the guy wires of a tent to unload
weight on the center pole (fig 1).5 Also described as the “serape
effect,”6 cocontraction further connects the stability of the
upper and lower extremities via the abdominal fascial system.
The effect becomes particularly important in overhead athletes
because that stability acts as a torque-countertorque of diago-
nally related muscles during throwing.6 The Queensland re-
search group1 has suggested the differentiation of local and
global muscle groups to outline the postural segmental control
function and general multisegmental stabilization function for
these muscles groups, respectively (table 2).
ANATOMY
General Overview
Stability and movement are critically dependent on the co-
ordination of all the muscles surrounding the lumbar spine.
Although recent research1,7,8has advocated the importance of a
few muscles (in particular, the transversus abdominis and mul-
tifidi), all core muscles are needed for optimal stabilization and
performance. To acquire this cocontraction, precise neural in-
put and output (which has also been referred to as propriocep-
tive neuromuscular facilitation) are needed.9 Pertinent anatomy
of the lumbar spine is reviewed below; however, readers
should refer to other texts for an extensive anatomic re-
view.1,5,10
Osseous and Ligamentous Structures
Passive stiffness is imparted to the lumbar spine by the
osseoligamentous structures. Tissue injury to any of these
structures may cause functional instability. The posterior ele-
ments of the spine include the zygapophyseal (facet) joints,
pedicle, lamina, and pars interarticularis. These structures are,
in fact, flexible. However, repetitive loading of the inferior
articular facets with excessive lumbar flexion and extension
causes failure, typically at the pars. The zygapophyseal joints
carry little vertical load except in certain positions such as
excessive lumbar lordosis.10 The intervertebral disk is com-
posed of the annulus fibrosis, nucleus pulposus, and the end-
plates. Compressive and shearing loads can cause injury ini-
tially to the endplates and ultimately to the annulus such that
posterior disk herniations result. Excessive external loads on
the disk may be caused by weak muscular control, thus causing
a vicious cycle where the disk no longer provides optimal
passive stiffness or stability. The spinal ligaments provide little
stability in the neutral zone. Their more important role may be
to provide afferent proprioception of the lumbar spine seg-
ments.11
Thoracolumbar Fascia
The thoracolumbar fascia acts as “nature’s back belt.” It
works as a retinacular strap of the muscles of the lumbar spine.
From the Department of Rehabilitation Medicine, University of Colorado, Denver,
CO (Akuthota); and Department of Physical Medicine and Rehabilitation, University
of Medicine and Dentistry of New Jersey, Newark, NJ (Nadler).
No commercial party having a direct financial interest in the results of the research
supporting this article has or will confer a benefit upon the author(s) or upon any
organization with which the authors is/are associated.
Reprint requests to Venu Akuthota, MD, Univ of Colorado Health Science Center,
PO Box 6508, Mail Stop F493, Aurora, CO 80045, e-mail:venu.akuthota@uchsc.edu.
0003-9993/04/8503-8950$30.00/0
doi:10.1053/j.apmr.2003.12.005
S86
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
The thoracolumbar fascia consists of 3 layers: the anterior,
middle, and posterior layers. Of these layers, the posterior layer
has the most important role in supporting the lumbar spine and
abdominal musculature. The transversus abdominis has large
attachments to the middle and posterior layers of the thoraco-
lumbar fascia.1 The posterior layer consists of 2 laminae: a
superficial lamina with fibers passing downward and medially
and a deep lamina with fibers passing downward and laterally.
The aponeurosis of the latissimus dorsi muscle forms the
superficial layer. In essence, the thoracolumbar fascia provides
a link between the lower limb and the upper limb.12 With
contraction of the muscular contents, the thoracolumbar fascia
acts as an activated proprioceptor, like a back belt providing
feedback in lifting activities (fig 1).
Paraspinals
There are 2 major groups of the lumbar extensors: the erector
spinae and the so-called local muscles (rotators, intertransversi,
multifidi). The erector spinae in the lumbar region are com-
posed of 2 major muscles: the longissimus and iliocostalis.
These are actually primarily thoracic muscles that act on the
lumbar via a long tendon that attaches to the pelvis. This long
moment arm is idealfor lumbar spine extension and for creat-
ing posterior shear with lumbar flexion.3
Deep and medial to the erector spinae muscles lay the local
muscles. The rotators and intertransversi muscles do not have
a great moment arm. Likely, they represent length transducers
or position sensors of a spinal segment by way of their rich
composition of muscle spindles. The multifidi pass along 2 or
3 spinal levels. They are theorized to work as segmental
stabilizers. Because of their short moment arms, the multifidi
are not involved much in gross movement. Multifidi have been
found to atrophy in people with low back pain7 (LBP).
Quadratus Lumborum
The quadratus lumborum is large, thin, and quadrangular
shaped muscle that has direct insertions to the lumbar spine.
There are 3 major components or muscular fascicles to the
quadratus lumborum: the inferior oblique, superior oblique,
and longitudinal fascicles. Both the longitudinal and superior
oblique fibers have no direct action on the lumbar spine. They
are designed as secondary respiratory muscles to stabilize the
twelfth rib during respiration. The inferior oblique fibers of the
quadratus lumborum are generally thought to be a weak lateral
flexor of the lumbar vertebrae. McGill13 states the quadratus
lumborum is a major stabilizer of the spine, typically working
isometrically.
Abdominals
The abdominals serve as a vital component of the core. In
particular, the transversus abdominis has received attention. Its
fibers run horizontally around the abdomen, allowing for hoop-
like stresses with contraction. Isolated activation of the trans-
versus abdominis is achieved through “hollowing in” of the
abdomen. The transversus abdominis has been shown to acti-
vate before limb movement in healthy people, theoretically to
stabilize the lumbar spine, whereas patients with LBP have a
delayed activation of the transversus abdominis.8 The internal
oblique has similar fiber orientation to the transversus abdomi-
nis, yet receives much less attention with regard to its creation
of hoop stresses. Together, the internal oblique, external
oblique, and transversus abdominis increase the intra-abdomi-
nal pressure from the hoop created via the thoracolumbar
fascia, thus imparting functional stability of the lumbar spine.3
The external oblique, the largest and most superficial abdom-
inal muscle, acts as a check of anterior pelvic tilt. As well, it
acts eccentrically in lumbar extension and lumbar torsion.5
Finally, the rectus abdominis is a paired, strap-like muscle of
the anterior abdominal wall. Contraction of this muscle pre-
dominantly causes flexion of the lumbar spine. In our opinion,
most fitness programs incorrectly overemphasize rectus abdo-
minis and internal oblique development, thus creating an im-
balance with the relatively weaker external oblique.14 The
external oblique can be stimulated by some of the exercises
described later, particularly those that emphasize isometric or
eccentric trunk twists (fig 2).15
Hip Girdle Musculature
The hip musculature plays a significant role within the
kinetic chain, particularly for all ambulatory activities, in sta-
Fig 1. Muscular cocontraction via the thoracodor-
sal fascia produces active stability, similar to the
support that guy ropes provide to a tent secured
against the wind. Adapted with permission from
Porterfield and DeRosa.5
Table 1: Synonyms and Near-Synonyms for Core Strengthening
Lumbar stabilization
Dynamic stabilization
Motor control (neuromuscular) training
Neutral spine control
Muscular fusion
Trunk stabilization
Table 2: Muscles of the Lumbar Spine
Global Muscles (dynamic, phasic,
torque producing)
Local Muscles (postural, tonic,
segmental stabilizers)
Rectus abdominis Multifidi
External oblique Psoas major
Internal oblique (anterior fibers) Transversus abdominis
Iliocostalis (thoracic portion) Quadratus lumborum
Diaphragm
Internal oblique (posterior
fibers)
Iliocostalis and longissimus
(lumbar portions)
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Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
bilization of the trunk and pelvis, and in transferring force from
the lower extremities to the pelvis and spine.16 Poor endurance
and delayed firing of the hip extensor (gluteus maximus) and
abductor (gluteus medius) muscles have previously been noted
in people with lower-extremity instability or LBP.17,18 Nadler
et al19 showed a significant asymmetry in hip extensor strength
in female athletes with reported LBP. In a prospective study,
Nadler et al20 showed a significant association between hip
strength and imbalance of the hip extensors measured during
the preparticipation physical and the occurrence of LBP in
female athletes over the ensuing year. Overall, the hip appears
to play a significant role in transferring forces from the lower
extremities to the pelvis and spine, acting as 1 link within the
kinetic chain.
The psoas major is a long, thick muscle whose primary
action is flexion of the hip. However, its attachment sites into
the lumbar spine give it the potential to aid in spinal biome-
chanics. During anatomic dissections, the psoas muscle has
been found to have 3 proximal attachment sites: the medial half
of the transverse processes from T12 to L5, the intervertebral
disk, and the vertebral body adjacent to the disk.10 The psoas
does not likely provide much stability to the lumbar spine
except in increased lumbar flexion.3 Increased stability require-
ments or a tight psoas will concomitantly cause increased,
compressive, injurious loads to the lumbar disks.
Diaphragm and Pelvic Floor
The diaphragm serves as the roof of the core. Stability is
imparted on the lumbar spine by contraction of the diaphragm
and increasing intra-abdominal pressure. Recent studies21 have
indicated that people with sacroiliac pain have impaired re-
cruitment of the diaphragm and pelvic floor. Likewise, venti-
latory challenges on the body may cause further diaphragm
dysfunction and lead to more compressive loads on the lumbar
spine.22 Thus, diaphragmatic breathing techniques may be an
important part of a core-strengthening program. Furthermore,
the pelvic floor musculature is coactivated with transversus
abdominis contraction.23
Exercise of the Core Musculature
Exercise of the core musculature is more than trunk strength-
ening. In fact, motor relearning of inhibited muscles may be
more important than strengthening in patients with LBP. In
athletic endeavors, muscle endurance appears to be more im-
portant than pure muscle strength.24 The overload principle
advocated in sports medicine is a nemesis in the back. In other
words, the progressive resistance strengthening of some core
muscles, particularly the lumbar extensors, may be unsafe to
the back. In fact, many traditional back strengthening exercises
may also be unsafe. For example, roman chair exercises or
back extensor strengthening machines require at least torso
mass as resistance, which is a load often injurious to the lumbar
spine.3 Traditional sit-ups are also unsafe because they cause
increased compression loads on the lumbar spine.15 Pelvic tilts
are used less often than in the past because they may increase
spinal loading. In addition, all these traditional exercises are
nonfunctional.3 In individuals suspected to have instability,
stretching exercises should be used with caution, particularly
ones encouraging end range lumbar flexion. The risk of lumbar
injury is greatly increased (1) when the spine is fully flexed and
(2) when it undergoes excessive repetitive torsion.25 Exercise
must progress from training isolated muscles to training as an
integrated unit to facilitate functional activity.
The neutral spine has been advocated by some as a safe place
to begin exercise.26 The neutral spine position is a pain-free
position that should not be confused with assuming a flat back
posture nor the biomechanic term “neutral zone” described by
Panjabi.4,27 It is touted as the position of power and balance.
However, functional activities move through theneutral posi-
Fig 2. Example of a movement awareness exercise: here, external
oblique muscles are activated with a controlled trunk twist.
S88 CORE STRENGTHENING, Akuthota
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
tion, thus exercises should be progressed to nonneutral posi-
tions.
Decreasing Spinal and Pelvic Viscosity
Spinal exercises should not be done in the first hour after
awakening because of the increased hydrostatic pressures in the
disk during that time.28 The “cat and camel” and the pelvic
translation exercises are ways to achieve spinal segment and
pelvic accessory motion before starting more aggressive exer-
cises. As well, improving hip range of motion can help dissi-
pate forces from the lumbar spine. A short aerobic program
may also be implemented to serve as a warmup. Fast walking
appears to cause less torque on the lower back than slow
walking.29
Grooving Motor Patterns
The initial core-strengthening protocol should enable people
to become aware of motor patterns. Some individuals who are
not adept at volitionally activating motor pathways require
facilitation in learning to recruit muscles in isolation or with
motor patterns. As well, some individuals with back injury will
fail to activate core muscles because of fear-avoidance behav-
ior.30 More time will need to be spent with these people at this
stage. Prone and supine exercises have been described to train
the transversus abdominis and multifidi. Biofeedback devices
were used by the Queensland group and others to help facilitate
the activation of the multifidi and transversus abdominis.1
Verbal cues may also be useful to facilitate muscle activation.
For example, abdominal hollowing is performed by transversus
abdominis activation; abdominal bracing is performed by co-
contraction of many muscles including the transversus abdo-
minis, external obliques, and internal obliques. However, most
of these isolation exercises of the transversus abdominis are in
nonfunctional positions. When the trained muscle is “awak-
ened,” exercise training should quickly shift to functional po-
sitions and activities.
Stabilization Exercises
Stabilization exercises can be progressed from a beginner
level to more advanced levels. The most accepted program
includes components from the Saal and Saal31 seminal dynamic
lumbar stabilization efficacy study (table 3). The beginner level
exercises incorporate the “big 3” (figs 3A–C) as described by
McGill.3 These include the curl-up, side bridge, and the “bird
dog.” The bird dog exercise (fig 3C) can progress from 4-point
kneeling to 3-point to 2-point kneeling. Advancement to a
physioball (fig 4) can be done at this stage (table 4). Sahr-
mann14 also describes a series of lower abdominal muscle
exercise progression (table 5).
Functional Progression
Functional progression is the most important stage in the
core-strengthening program. A thorough history of functional
activities should be taken to individualize this part of the
program. Patients should be given exercises in sitting, standing,
and walking. Sitting is often a problematic position, particu-
larly with lumbar disk injury. Sitting with lumbar lordosis
totally flattened shifts the center of gravity anteriorly, relative
Fig 3. The basic exercise triad for most stabilization programs con-
sists of the (A) curl-up, (B) side bridge, and (C) bird dog exercises.
S89CORE STRENGTHENING, Akuthota
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
to the standing position. This shift, in addition to increased hip
flexor activity (such as with sitting at the edge of a chair),
causes increased compressive loads on the lumbar spine.14
Education on proper sitting and standing ergonomics, along
with so-called “movement awareness” exercises, also have
been advocated by some to thwart LBP.32 Juker et al15 per-
formed a seminal study on quantitative electromyographic ac-
tivity with different positions and exercise. Although quiet
standing requires little electromyographic activation of core
musculature, sitting with an isometric twist or sitting with hip
motion produces more activation of core musculature. Core
musculature should be trained to endure these functional ac-
tivities.
Core Strengthening for Sports: Moving Past Remedial
Core Training
Because sports activity involves movement in the 3 cardinal
planes—sagittal, frontal, and transverse—core musculature
must be assessed and trained in these planes. Often, transverse
or rotational movements are neglected in core training. Assess-
ment tools for functional evaluation of these movements
(lunge, step-down, single leg press, balance, reach) have not
been well validated but have proven to be reliable.33 However,
the multidirectional reach test and the star-excursion balance
test (multidirectional excursion assessments in all cardinal
planes) are both reliable and valid tests of multiplanar excur-
sion.34,35 Single-leg squat tests (with or without step downs)
also serve as validated tools of assessment.35 These evaluative
tools help one select an individualized core training program,
emphasizing areas of weakness and sports-specific movements.
Core training programs for sports are widely used by
strengthening and conditioning coaches at the collegiate and
professional levels. An example of Gambetta’s program36 is
provided (table 6, fig 5). Core strength is an integral component
of the complex phenomena that comprise balance. Balance
requires a multidimensional interplay between central, periph-
eral, sensory, and motor systems. Training the domain of
balance is important for functional activities. Progression to
labile surfaces may improve balance and proprioception. Dif-
ferent fitness programs37 incorporate various aspects of core
strengthening and may be a useful way to maintain compliance
in many individuals (table 7).
Efficacy of Core-Strengthening Exercise
The clinical outcomes of core-strengthening programs have
not been well researched. Studies are hampered by the lack of
consensus about what constitutes a core-strengthening pro-
gram. Some describe remedial neuromuscular retraining,
whereas others describe sports-specific training and functional
education. To our knowledge, no randomized controlled trial
exists on the efficacy of core strengthening. Most studies are
prospective, uncontrolled, case series.
Core Strengthening to Prevent Injury and Improve
Performance
In 2002, Nadler et al38 attempted to evaluate the occurrence
of LBP both before and after incorporation of a core-strength-
ening program. The core-strengthening program included sit-
ups, pelvic tilts, squats, lunges, leg presses, dead lifts, hang
cleans, and Roman chair exercises. Although the incidence of
LBP decreased by 47% in male athletes, this reduction was not
statistically significant; the overall incidence of LBP slightly
increased in female athletes despite core conditioning. This
negative result may have resulted from the use of some unsafe
exercises, such as Roman chair extensor training.3,39 Further,
Table 4: Physioball Exercises for the Core
Abdominal crunch
Balancing exercise while seated
“Superman” prone exercise
Modified push-up
Pelvic bridging
Table 6: Advanced Core Program Used by Gambetta36
Body weight and gravitational loading (push-ups, pull-ups, rope
climbs)
Body blade exercises
Medicine ball exercises (throwing, catching)
Dumbbell exercises in diagonal patterns
Stretch cord exercises
Balance training with labile surfaces
Squats
Lunges
Fig 4. The pelvic bridging exercise performed with a physioball.
Table 5: Sahrmann’s Lower Abdominal Exercise Progression
Base position
cue
Supine with knees bent and feet on floor;
spine stabilized with “navel to spine”
Level 0.3 Base position with 1 foot lifted
Level 0.4 Base position with 1 knee held to chest
and other foot lifted
Level 0.5 Base position with 1 knee held lightly to
chest and other foot lifted
Level 1A Knee to chest (�90° of hip flexion) held
actively and other foot lifted
Level 1B Knee to chest (at 90° of hip flexion)and the subject’s feet were placed flat on the
floor. Each isometric curl-up hold lasted approximately
6 seconds, from which the last 2 seconds were selected
for analysis. Two minutes of rest was provided between
tasks.
Data Collection
Electromyographic signals were recorded from 4 differ-
ent abdominal sites on the right and left sides of the
body. Pairs of silver-silver chloride electromyographic
(EMG) surface electrodes were placed 3 cm apart, center
to center, on the skin over the following muscles: upper
rectus abdominis muscle (approximately 3 cm lateral
and 5 cm superior to the umbilicus), lower rectus
abdominis muscle (approximately 3 cm lateral and 5 cm
inferior to the umbilicus), external oblique muscle
Figure 1.
Four different curl-up exercises used in the study: (A) curl-up on stable bench (task A), (B) curl-up with the upper body over a labile gym ball and with
feet flat on the floor (task B), (C) curl-up with the upper body over a labile gym ball and with feet on a bench (task C), (D) curl-up with the upper body
supported by a labile wobble board (task D).
566 . Vera-Garcia et al Physical Therapy . Volume 80 . Number 6 . June 2000
(approximately 15 cm lateral to the umbilicus), and
internal oblique muscle (halfway between the anterior
superior iliac spine of the pelvis and the midline, just
superior to the inguinal ligament). The EMG signals
were amplified to produce approximately 64 V, then
A/D converted via a 12-bit, 16-channel A/D converter at
1,024 Hz (full-wave rectified and low-pass filtered with a
Butterworth filter at 2.5 Hz to create a linear envelope of
the activity). The average value of the muscle activity
over the 2-second sample was then normalized to each
subject’s maximal myoelectric activity (or maximal vol-
untary contraction [MVC]) at each muscle site
(obtained through a series of maximal exertion tasks9
and expressed as a percentage of this value). Maximal
voluntary contractions were obtained in isometric max-
imal exertion tasks. The subjects were manually braced
for flexor moment while in a sit-up position for the
rectus abdominis muscle; the same posture was used for
the oblique muscles, but subjects also attempted isomet-
ric twisting efforts (although no twist took place).
Slide film recorded the external body segment position
in the sagittal plane of the subjects during their perfor-
mance of each curl-up exercise to confirm correct
positioning. It was important to confirm that the torso
posture remained constant between tasks to ensure valid
EMG signals from the muscles underneath the
electrodes.
Data Reduction
These abdominal challenging activities were also ranked
according to their average EMG amplitude. A 2-way
analysis of variance was performed on the maximum
EMG levels from each task for each of the 4 abdominal
muscle sites (P#.05). A Tukey Honestly Significant
Difference post hoc test was used to identify specific
differences.
Results
Performing a curl-up on the stable bench (task A, Fig. 1)
resulted in the lowest amplitude of abdominal muscle
activity (for all muscles) observed in any task (approxi-
mately 21% of MVC for the rectus abdominis muscle)
(Tab. 1). Differences in activity among different exer-
cises are shown in Table 2. The other 3 exercises
performed on labile surfaces approximately doubled the
abdominal muscle activity. Furthermore, although per-
forming the curl over the gym ball with the feet on the
floor (task B) generally doubled activity in the rectus
abdominis muscle, activity in the external oblique mus-
cle increased approximately fourfold. For all exercises,
the rectus abdominis muscle was much more active (in
percentage of MVC) than the oblique muscles. The
internal oblique muscle was more active than the exter-
nal oblique muscle with the exception of task B, where
the subject’s feet were on the floor and there was the
greatest possibility of rolling laterally off the ball. In this
task, there was much more co-contraction of the exter-
nal oblique muscle with the rectus abdominis muscle
when compared with other tasks (this is shown in the
ratios of muscle activity in Figs. 2 and 3). This task was
the most demanding in terms of maintaining whole-body
stability.
Another question of interest to us was whether people
are able to preferentially recruit upper versus lower
portions of the rectus abdominis muscle. Relative ratios
of the upper and lower portions of the rectus abdominis
Table 1.
Average Muscle Activity Normalized as a Percentage of Maximal Voluntary Contraction for the Four Curl-up Tasks and for the Right and Left
Sides of the Rectus Abdominis, External Oblique, and Internal Oblique Musclesa
Right Side
Exercise
URAR LRAR OER OIR
Average SD Average SD Average SD Average SD
CU 21.76 10.6 20.87 10.5 4.73 4.3 11.53 7.5
CUBF 46.71 22.0 54.76 17.0 21.21 12.5 19.27 7.9
CUBB 33.44 13.3 34.49 8.2 9.24 6.07 17.11 8.3
CUPT 38.70 17.7 36.59 11.5 7.37 5.92 16.14 10.0
Left Side
Exercise
URAL LRAL OEL OIL
Average SD Average SD Average SD Average SD
CU 20.58 12.1 19.83 9.7 4.62 2.2 10.98 8.4
CUBF 46.50 27.2 52.97 22.1 19.75 10.0 19.79 7.4
CUBB 35.09 17.6 34.44 11.7 11.28 7.7 16.47 9.8
CUPT 39.75 28.2 36.02 13.4 9.12 7.0 16.08 10.2
a CU5curl-up on stable bench (task A); CUBF5curl-up with the upper body over a labile gym ball and with both feet flat on the floor (task B); CUBB5curl-up
with the upper body over a labile gym ball and with both feet on a bench (task C); CUPT5curl-up with the upper body supported by a labile wobble board (task
D); URAR5upper portion of rectus abdominis muscle, right side; LRAR5lower portion of rectus abdominis muscle, right side; URAL5upper portion of rectus
abdominis muscle, left side; LRAL5lower portion of rectus abdominis muscle, left side; OER5external oblique muscle, right side; OIR5internal oblique muscle,
right side; OEL5external oblique muscle, left side; OIL5internal oblique muscle, left side.
Physical Therapy . Volume 80 . Number 6 . June 2000 Vera-Garcia et al . 567
III
III
III
III
III
III
III
III
III
I
muscle (Fig. 4) indicate that the upper region was more
active in task D, in which the subject’s upper body was
supported on the wobble board, whereas the lower
region of the rectus abdominis muscle was proportion-
ally more active in task B, in which the subject’s upper
body was over the gym ball with the feet on the floor. For
the other 2 tasks, upper and lower rectus abdominis
muscle activity was almost the same. We are still unable
to interpret the data as proof of the ability to preferen-
tially recruit different sections of this muscle. Rather, the
differences may have been to due to small geometric and
postural changes.
Discussion
Performing curl-up exercises on labile surfaces appears
to increase abdominal muscle activity. This increase in
muscle activity is probably due to the increased require-
ment to enhance spine stability and whole-body stability
to reduce the threat of falling off the labile surface.
Furthermore, in order to enhance this stability, it
appears that the motor control system selected to
increase external oblique muscle activity more than the
other abdominal muscles. The use of labile surfaces
appears to increase muscle activity levels and coactiva-
tion, further challenging endurance capabilities; how-
ever, there is no doubt that the spine pays an additional
load penalty for this in increased muscle activity. Given
the magnitude of spinal loads observed in tasks similar to
those studied here,7 the additional load that occurs with
use of labile surfaces may be of concern only for the
most fragile of patients.
Although little literature exists to compare with the
results of our study, the measurements of abdominal
Table 2.
Differences in Muscle Activity Among the Different Exercisesa
Muscle
URAR LRAR OER OIR URAL LRAL OEL OIL
CU/CUBF * * * *
CU/CUBB
CU/CUPT
CUBF/CUBB * *
CUBF/CUPT * *
CUBB/CUPT
a Asterisk (*) indicates difference in average electromyographic activity as a percentage of maximal voluntary contraction (P,.05, repeated-measuresheld
actively and other foot lifted
Level 2 Knee to chest (at 90° of hip flexion) held
actively and other foot lifted and slid
on ground
Level 3 Knee to chest (at 90° of hip flexion) held
actively and other foot lifted and slid
not on ground
Level 4 Bilateral heel slides
Level 5 Bilateral leg lifts to 90°
Data from Sahrmann.14
S90 CORE STRENGTHENING, Akuthota
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
the exercises chosen for the study included only frontal and
sagittal plane movements, which may have affected the results.
Future studies incorporating exercises in the transverse plane
may help to clarify the relation between surrounding core-
strengthening exercises and LBP.
Most other research on musculoskeletal injury prevention
has focused on decreasing the incidence of anterior cruciate
ligament injury. Those training programs40 work on providing
a proprioceptively rich environment at various planes and
degrees. Muscle cocontraction is stimulated using short-loop
proprioception to provide joint stability. In short, preventative
training programs are activations of neuromuscular control
patterns.
Research40 shows that a few essential ingredients can en-
hance neuromuscular control. These components include joint
stability (cocontraction) exercises, balance training, perturba-
tion (proprioceptive) training, plyometric (jump) exercises, and
sports-specific skill training. All these regimens should be
preceded by a warmup. Perturbation programs, described by
Caraffa et al,40 feature exercises that challenge proprioception
via wobble boards, roller boards, disks, and physioballs. These
programs work at the afferent portion of the neuromuscular
control loop and provide stimulation of different propriocep-
tors. In a prospective study, Hewett et al41 developed a plyo-
metric jump training program that reduced knee injuries in
female athletes. Plyometric training emphasizes loading of
joints and muscles eccentrically before the unloading concen-
tric activity. Plyometrics use the biomechanic principles of
triplanar pronation and supination. Pronation is a physiologic
multiplanar motion, typically described for the ankle and foot
joints. It involves eccentrically decelerating joints so that shock
absorption and potential energy are created. On the other hand,
supination involves concentrically created acceleration so that
propulsion is achieved.37 Specific core stability programs as a
form of prevention of lower-extremity injury have not been
well studied. Further, there are no focused studies of core-
strengthening or similar programs that show improved perfor-
mance with functional activity or sporting activity. Nonethe-
less, the lay literature has promoted many different programs
for performance enhancement.
Core Strengthening for Treatment of Back Pain
The seminal article31 describing a core stability program was
performed as an uncontrolled prospective trial of “dynamic
lumbar stabilization” for patients with lumbar disk herniations
creating radiculopathy. The impact of therapeutic exercise
alone was difficult to ascertain because of the offering of other
nonsurgical interventions, including medication, epidural ste-
roid injections, and back school. The exercise training program
was well outlined and consisted of a flexibility program, joint
mobilization of the hip and the thoracolumbar spinal segments,
a stabilization and abdominal program (see table 2), a gym
program, and aerobic activity. Successful outcomes were re-
ported in 50 of 52 subjects (96%). The described dynamic
lumbar stabilization program resembles the current concept of
a core stability program without the higher level sports-specific
core training. Several other authors42,43 have described similar
programs.
Work-hardening or functional restoration programs have
also been used for the injured worker with back pain.44 The
exercise training program uses Nautilus equipment for progres-
sive resistance strengthening of isolated muscle groups. An
emphasis is placed on reaching objective goals. The training
program differs from the current concept of core strengthening
in that it emphasizes nonfunctional isolation exercises over
motor relearning.
Although a recent Cochrane review found that exercise is an
effective treatment of LBP, no specific exercise programs
showed a clear advantage for that application.45
CONCLUSIONS
Core strengthening has a theoretical basis in treatment and
prevention of various musculoskeletal conditions. Other than
studies in the treatment of LBP, research is severely lacking.
With the advancement in the knowledge of motor learning
theories and anatomy, core-stability programs appear on the
cusp of innovative new research.
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Table 7: Fitness Programs That Follow Core-
Strengthening Principles
Pilates
Yoga (some forms)
Tai Chi
Feldenkrais
Somatics
Matrix dumb-bell program37
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Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
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S92 CORE STRENGTHENING, Akuthota
Arch Phys Med Rehabil Vol 85, Suppl 1, March 2004
The Importance of Developing a 
Primary Core Stability Protocol
Angela M. Homan, SPT
Duke University 
Doctor of Physical Therapy Intern
SportsMedicine of Atlanta 
Dr Robert E DuVall
PT, DHSc, MMSc, ATC, OCS, SCS, FAAOMPT, DAC, MTC, PCC, CSCS
Shenandoah University, Associate Professor
Alabama State and Northeastern University, Clinical Assistant Professor
SportsMedicine of Atlanta, Inc.
Residency & APTA Fellowship Curricula Director
reduvall@bellsouth.net www.SportsMedicineofAtlanta.com
SportsMedicine of Atlanta, Inc.
mailto:reduvall@bellsouth.net
NMR Research Shown Beneficial 
to Reduce Pain and Disability
 "In America alone, the treatment cost of back pain is 
estimated to be $86 billion per year or 9% of the country's 
total health expenditure. The search for new ways to 
manage this old problem is critical in order to improve the 
health and quality of life of individuals who struggle with 
this condition.“
 According to researchers not only do patients feel less pain, 
but patients performing these types of exercises are able to 
be more physically active and experience positive effects 
over a longer period of time than those who receive other 
treatments.
Macedo, Luciana G. Maher, Christopher G. Latimer, Jane. McAuley, James H. Motor Control Exercise for 
Persistent, Nonspecific Low Back Pain: A Systematic Review. PTJ 2009;89(1).9-95.
Primary Core
Transverse Abdominis (TrA)
Multifidus
Transverse Abdominis Anatomy
 Origin: inner surface of cartilages of lower 6 
ribs, interdigitation with diaphragm, 
thoracolumbar fascia, anterior ¾ of internal lip 
of iliac crest, and lateral 1/3 of inguinal ligament
 Insertion: linea alba (broad aponeurosis), pubic 
crest, and pecten pubis
 Nerve Innervation: T7-T12, L1
(iliohypogastric and ilioinguinal)
Kendall et al.
Actions of TrA
 Flattens abdominal wall and compress the 
abdominal viscera
 Decrease infrasternal angle of ribs in expiration 
(upper portion of TrA)
 No Action in lateral trunk flexion, except to 
compress the viscera and to stabilize linea alba 
(= better action of anterolateral trunk muscles)
Kendall et. al.
Weakness in TrA (observations)
 Standing position: Permits bulging of 
anterior abdominal wall (= increases 
lordosis)
 Supine position: during flexion a lateral 
bulge tends to occur
 Prone position: hyperextension of 
trunk with lateral bulge tends to occur
Kendall et al.
Multifidus Anatomy
 Origin: Sacral region: posterior surface of sacrum, 
medial surface of posterior iliac spine & postero-
sacroiliac ligaments. Lumbar, thoracic, & cervical 
regions: transverse processes of L5-C4
 Insertion: Spanning two to four vertebrae, 
inserting onto spinous process of one of 
vertebra above from last lumbar to axis (second 
cervical vertebra
 Nerve Innervation: Spinal
Kendall et al.
Actions of Multifidis
 Extends vertebral column and rotation toward 
opposite side.
Kendall et al.
Functions of TrA & Deep Multifidus
 Deep Multifidus and TrA provide intersegmental 
spinal stability
 Deep fibers of Multifidus control intervertebral 
motion
 Superficial fibers of Multifidus control spine 
orientation
Moseley GL, Hodges PW, Gandevia SC. Deep and superficial fibers of the lumbar multifidus muscle are differentially active during voluntary arm movements. Spine. 
2002;27:E29–E36.
TrA Muscle Activation Patterns
 TrA may be controlled independently of the motor 
command for limb movement in contrast to the other 
abdominal muscles.
 HodgesPW, Richardson CA. Transversus abdominis and the superficial abdominal muscles are controlled independently in a postural task. 
Neuroscience Letters. 1999;265:91-94.
 Feedforward TrA activation pattern with Lower 
extremity movement
 Hodges P, Richardson C. Contraction of the abdominal muscles associated with movement of the lower limb. Physical Therapy. 1997;77:132-144.
 Feedforward activation TrA activation pattern with 
upper extremity movement 
 Hodges P, Richardson C. Feedforward contraction of transversus abdominis is not influencedby the direction of arm movement. Experimental Brain 
Research. 1997;114:362-370.
 Preparatory trunk movement precedes upper extremity 
movement 
 Hodges P, Cresswell AG, Daggfeldt K, Thorstensson A. Preparatory trunk motionaccompanies rapid upper limb 
movement. Experimental Brain Research. 1999;124:69-79.
 Hodges P, Cresswell AG, Daggfeldt K, Thorstensson A. Three dimensional preparatory trunk motion precedes 
asymmetrical upper limb movement. Gait and Posture. 2000;11:92-101.
Core Dysfunction: Anatomy
Transverse Abdominis:
 Isometric Knee extension/flexion 
tasks identified subjects with LBP had 
smaller increase in TrA thickness and 
less EMG activity 
Ferreira PH, Ferreira, Hodges PW. Changes in recruitment of the abdominal muscles in people with low back pain 
ultrasound measurement of muscle activity. Spine. 2004;29:2560-2566.
Core Dysfunction: Anatomy
Multifidus:
 Atrophy of multifidus has been used as a rationale for 
spine stabilizing exercises.
 Barker et al, found selective ipsilateral atrophy of 
multifidus in patients with unilateral LBP (low back 
pain)
 MRI analysis of the CSA of Multifidus
 At level of pain: 21.7 % decrease
 Above level of pain: 15.8% decrease
 Below level of pain: 16.8% decrease 
 Decreased CSA at level of pain was positively correlating with 
duration of pain.
Barker KL, Shamley DR, Jackson D. Changes in the cross-sectional area of multifidus and psoas in patients with unilateral back 
pain. The relationship to pain and disability. Spine. 2004;29:E515-E519.
Core Dysfunction: Activation 
Patterns
 Subjects with chronic LBP do not pre-activate 
TrA prior to rapid upper and lower limb tasks. 
Barr KP, Griggs M, Cadby T: Lumbar stabilization: Core concepts and current literature, part 1. Am J Phys Med Rehabil. 2005;84:473-480.
Hodges P, Richardson C. Inefficient muscular stabilisation of the lumbar spine associated with low back pain: a motor control
evaluation of transversus abdominus. Spine. 1996;21:2640-2650.
 Onset of internal obliques, multifidus, & 
gluteus maximus was delayed on the 
symptomatic side (>20ms)= no feed-forward 
activation in subjects with sacroiliac joint pain
Hungerford B, Gilleard W, Hodges P, Evidence of altered lumbopelvic muscle recruitment in the presence of sacroiliac joint pain. Spine. 
2003;28:1593-1600.
TrA Muscle Activation
 Three different techniques used in clinical 
practice:
 Drawing-in Maneuver
 Abdominal Bracing
 Posterior Pelvic Tilt
 Drawing-in Maneuver is more selective in 
coactivating the TrA and multifidus than the 
other 2 techniques.
 Hodges, PW, Richardson, GA, and Jull, G: Evaluation of the relationship between laboratory and clinical tests of transversus abdominis function. Physiother 
Re Internat 1(1):30, 1996.
 Richardson, C, Jull, G, et al: Techniques for activae lumbar stabilisation for spinal protection: A pilot study. Austral J Physiother 38:105, 1992.
Drawing-In Manuever
 Recommended for stabilization training
 Functions to ↑ intra-abdominal pressure by 
inwardly displacing the abdominal wall.
 Increases CSA (cross sectional area) of TrA on 
MRI (TrA contracts bilaterally to form a 
musculofascial band that appears to tighten like 
a corset and most likely improves stability of 
lumbopelvic region.
 Hides J, Wilson S, Stanton W, et al. An MRI investigation into the function of the transversus abdominis muscle during 
“drawing-In” of the abdominal wall. Spine. 2006;31:E175-E178
Drawling-in Maneuver:
 Patient starts in hook-lying position and assumes a 
neutral spine position & attempts to maintain it 
while drawing in and hollowing the abdominal 
muscles.
Kendal, F, McCreary, E, and Provance, PG: Muscles: Testing and Function, ed 4. Williams & Wilkins, Baltimore, 1993.
 Subtle posterior pelvic tilt & flattening of lumbar spine.
 No flaring of lower ribs, bulging out of abdominal wall 
or ↑ pressure through feet.
 Instructions: draw the “belly button” up and in toward 
the spine while exhaling
Feedback Techniques
 If patient is having difficulty activating the 
Transverse Abdominis, the following has been 
used to assist with learning:
 Pressure transducer for clinical testing and 
visual feedback (Pressure Bio-Feedback 
Chatanooga Pacific)
 Biofeedback with surface electrodes
Hagins, M, et al: Effects of practice on the ability to perform lumbar stabilization exercises. J Orthop Sports Phys Ther 29(9):546, 1999.
Jull, GA, and Richardson, CA: Rehabilitation of Active Stabilization of the Lumbar Spine. In Twomy, LT and Taylor (eds): Physical Therapy of the 
Lumbar Spine, ed 2. Churchill Livingstone, New Yourk, 1994.
Richardson, C, Jull, G, et al: Techniques for active lumbar stabilization for spinal protection: A pilot study. Austral JPhysiother 38:105, 1992.
Richardson C, and Jull, G: An historical perspective on the development of clinical techniques to evaluate and treat the active stabilizing system of the 
lumbar spine. Austral J Physiother Monograph 1:5, 1995.
Visual Feedback- hook-lying
 Place small inflatable bladder with pressure sensor 
(similar to BP cuff) under lumbar spine and inflate it to 
40-mm Hg.
 Correct Activation: 10-mm Hg increase in pressure
 Large increase occurs if activating rectus abdominis 
and/or increased lumbar flexion (posterior pelvic tilt).
 No change in pressure = no activation of TrA
Visual Feedback- hook-lying
Biofeedback with surface electrodes
 Electrodes placed over rectus abdominis & 
external obliques (near attachment on the 8th
rib).
 Correct activation: minimal to No activation of 
these muscles
 Can be used in conjunction with inflatable cuff.
Abdominal Bracing
 Occurs by setting the abdominals and actively 
flaring out laterally around the waist
 Technique has been taught years
 It has been shown to activate the oblique 
abdominal muscles
Richardson, C, Jull, G, et al: Techniques for active lumbar stabilization for spinal protection: A pilot study. Austral JPhysiother 38:105,1992.
Posterior Pelvic Tilt
 Activates Rectus Abdominis: it is NOT a core 
spinal stabilization muscle
 Only useful for teaching awareness of the 
movement of the pelvis and lumbar spine.
 Activated when patient explores lumbar ROM 
with pelvic tilts to find neutral spine position.
Richardson, C, Jull, G, et al: Techniques for active lumbar stabilization for spinal protection: A pilot study. Austral JPhysiother 38:105,1992
Lower Abdominal Progression
 Levels developed by Shirley A. Sahrmann
 Purposes:
 To improve the performance of abdominal muscles 
(external obliques, rectus abdominis, transverse 
abdominis)
 To learn to prevent lumbar spine motions associated with 
leg motion
Starting Position -Sahrmann
 Supine with hips and knees flexed and feet on 
the floor. Contract abdominal muscles by 
flattening the abdomen and reducing the 
arch in the lumbar spine. Patient is instructed to 
place fingers on abdominal muscles and “pull 
the navel in toward the spine.”
Level 0.3 (E1)-Sahrmann
 Lift one foot with alternate foot on floor
 Method:
 Flex one hip while keeping knee flexed.
 Return the LE to starting position and repeat with 
opposite LE.
Level 0.4 (E2)- Sahrmann
 Hold one knee to chest & lift the alternate foot
 Method: 
 Flex one hip and use hands to hold knee to chest.
 While maintaining contraction of abdominal muscles, flex the 
other hip. Hold fora count of 3 and return the LE to starting 
position.
 Perform with opposite extremity.
 Repeat 5-6 times
Level 0.5- Sahrmann
 LIGHTLY hold one knee toward the chest and lift 
the alternate foot
 Methods: 
 Flex one hip and use one hand to hold knee to chest, but 
hold it less firmly than level E2 (0.4).
 While maintaining contraction of abdominal muscles, flex 
other hip.
 Hold for a count of 3 and return the LE to starting position
 Perform with the opposite extremity.
 Repeat 5-6 times
Level 1A- Sahrmann
 Flex the hip to > 90˚and lift the alternate foot
 Methods:
 Contract the abdominal muscles; flex one hip to > 90 degrees 
by lifting the foot from the table.
 Contract the abdominal muscles and flex the other hip by 
lifting the foot off the table.
 Maintain the contraction of 
abdominal muscles and lower 
the legs, one at a time, to 
starting position.
 Repeat by starting the 
sequence with opposite leg.
Level 1B- Sahrmann
 Flex the hip to 90˚ and lift the other foot.
 Methods: 
 Contract abdominal muscles and flex one hip to 90 degrees.
 Contract abdominal muscles and lift other leg to same 
position. Maintain contraction of abdominal muscles, lower 
the legs one at a time to starting position.
 Repeat by starting the sequence 
with the opposite LE.
 Repeat, alternating legs, correctly
10 times to progress to Level 2.
Level 2-Sahrmann
 Flex one hip to 90˚ and lift & slide the other foot to extend 
the hip and knee.
 Methods: 
 Contract abdominal muscles and flex hip to 90 degrees, lifting foot off 
the table.
 Maintain contraction of abdominal muscles; lift other leg up to same 
position.
 Maintain one leg at 90 degrees, place other heel on table and slowly slide 
heel along table until hip and knee are extended.
 Return leg to starting position by sliding hell along table.
 Repeat extension motion with other LE and return it to starting position.
 Repeat, alternating legs, correctly 10 times to progress to Level 3.
Level 3-Sahrmann
 Flex one hip to 90 degrees, and lift the foot and extend the 
leg without touching the support surface. 
 Methods:
 Flex hip to 90 degrees, lifting foot from the table.
 Maintain contraction of abdominal muscles and lift other leg up to same 
position.
 Maintain one hip at 90 degrees, extend the other hip and knee while 
holding the foot off the table until hip and knee are resting in an 
extended position on the table.
 Return leg to the hip and knee flexed position.
 Maintain contraction of abdominal muscles, extend and lower the other 
leg and return it to the 90 degree position.
 Repeat, alternating legs, correctly 10 times to progress to Level 4.
Level 4-Sahrmann
 Slide both feet along the supporting surface into 
extension and return to flexion
 Methods:
 Begin in supine position with both legs in extension. 
Contract abdominal muscles and slide heels along table, 
flexing both hips and knees while bringing them toward the 
chest.
 Once hips and knees are flexed, pause
and reinforce abdominal contraction. 
 Slide both legs back into extension. 
 Repeat correctly 10 times to 
progress to Level 5
Level 5-Sahrmann
 Lift both feet off the supporting surface, flex the hips to 90 
degrees, extend the knees, and lower both extremities to 
supporting surface.
 Methods: 
 Begin with LE extended position.
 Contract abdominal muscles 
while simultaneously flex hips 
and knees, lifting both feet
off the table to bring the hips 
to 90 degrees.
 Reinforce the contraction of 
abdominal muscles, extend the 
knees and lower LEs to table.
Primary Core Protocols
 Transverse Abdominis (Levels I-V)
 Multifidus (Levels I-III)
http://lowerabexercises.blogspot.com/
The TrA Level Progression
 These proposed levels were designed from the 
research and are clinically applied to strengthen 
the Transverse Abdominis in isolation.
 Purpose:
 To have a common terminology among practicing 
clinicians in the same physical therapy setting.
 To improve the performance of TrA muscle.
 To prevent lumbar spine motion (neutral spine) 
during functional activity. 
Starting Position: TrA Level I
 Method:
 Supine with hips & knees flexed and feet on the 
floor. 
 Patient is instructed keep a Neutral lumbar spine 
using the „Drawing-in Maneuver‟ and place two 
fingers on transverse abdominus and one hand on 
superficial abdominal muscles. 
 Next, patient is asked to “pull the navel in toward 
the spine” without tightening superficial abdominal 
muscles and only the TrA.
TrA Level I
 Level I will be the starting position for all levels 
I-V.
TrA Level II
 Lift one foot to 90 
degrees with alternate 
foot on table
 Method:
 Contract TrA and flex one 
hip to 90 degrees while 
keeping knee flexed.
 Return the LE to starting 
position and repeat with 
opposite LE.
TrA Level III
 Flex the hip to 90˚ and lift the other foot.
 Methods: 
 Contract TrA and flex one hip to 90 degrees.
 Lift other leg to same position. While maintaining contraction 
of TrA, lower the legs one at a time to starting position.
 Repeat by starting the sequence 
with the opposite LE.
 Repeat, alternating legs, correctly
10 times to progress to Level 4.
TrA Level III
TrA Level IV
 Flex one hip to 90 degrees, and lift the other foot. Extend 
the one leg without touching the support surface. 
 Methods:
 Flex hip to 90 degrees, lifting foot from the table.
 Maintain contraction of TrA and lift other leg up to same 
position.
 Maintain one hip at 90 degrees, extend the other hip and knee 
while holding the foot off the table.
 Return leg to the hip and knee flexed position.
 Maintain contraction of abdominal muscles, extend other leg 
and return it to the 90 degree position.
 Repeat, alternating legs, correctly 10 times to progress to 
Level 5.
TrA Level IV
TrA Level V
 Flex the hips to 90 degrees and extend the knees 
without touching the support surface.
 Methods:
 Flex hip to 90 degrees, lifting foot from the table.
 Maintain contraction of TrA and lift other leg up to 
same position.
 Extend both hips and knees while holding the feet 
off the table.
 Return legs to the hip and knee flexed position.
 Repeat correctly 10 times.
TrA Level V
Multifidus Level Progression (I-III)
 These proposed levels were designed from the 
research and are clinically applied to strengthen 
the Multifidus in isolation.
 Purpose:
 To have a common terminology among practicing 
clinicians in the same physical therapy setting.
 To improve the performance of Multifidus muscle.
 To prevent lumbar spine motion (neutral spine) 
during functional activity.
Multifidus Level Ia
 Start position: 
Quadriped 
 Neutral lumbar spine
 Have patient lift one 
lower extremity (LE) ( 
knee) ~ 1 inch from 
table
 Hold position ~ 5 
seconds
 Alternate with the 
other LE.
Multifidus Level Ib
 Start position: Quadriped 
 Neutral lumbar spine
 Have patient lift one LE 
(knee) and the 
contralateral upper 
extremity (UE) (hand) ~ 1 
inch from table
 Hold ~ 5 seconds
 Alternate with the other 
LE and contralateral UE
Multifidus Level II
 Starting position: Prone
 Maintain neutral lumbar spine (i.e. placement of 
pillow)
 Lift one UE and contralateral LE from the table
 Alternate with other UE and contralateral LE. 
Multifidus Level III
 Starting position: 
standing on stool facing 
wall
 Extend one UE and 
contralateral LE
 Alternate with other UE 
and contralateral LE
Clinical Biomechanics: 
Intervention Skill Sets
NMR (97112)
Longus Colli Isolation
Text References
 Kendall, FP et al. Muscles Testing and Function 
with Posture and Pain. Fifth edition, 2005.
 Sahrmann, SA. Diagnosis and the Treatment of 
Movement Impairment Syndromes. 2002.
 Kisner, C & Colby LA. Therapeutic Exercise: 
Foundations and Techniques. Fourth edition, 
2002.D
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RELATIONSHIP BETWEEN CORE STABILITY,
FUNCTIONAL MOVEMENT, AND PERFORMANCE
TOMOKO OKADA, KELLIE C. HUXEL, AND THOMAS W. NESSER
Exercise Physiology Laboratory, Athletic Training Department, Indiana State University, Terre Haute, Indiana
ABSTRACT
Okada, T, Huxel, KC, and Nesser, TW. Relationship between
core stability, functional movement, and performance.
J Strength Cond Res 25(1): 252–261, 2011—The purpose
of this study was to determine the relationship between core
stability, functional movement, and performance. Twenty-eight
healthy individuals (age = 24.4 6 3.9 yr, height = 168.8 6 12.5
cm, mass = 70.2 6 14.9 kg) performed several tests in 3
categories: core stability (flexion [FLEX], extension [EXT], right
and left lateral [LATr/LATl]), functional movement screen (FMS)
(deep squat [DS], trunk-stability push-up [PU], right and left
hurdle step [HSr/HSl], in-line lunge [ILLr/ILLl], shoulder mobility
[SMr/SMl], active straight leg raise [ASLRr/ASLRl], and rotary
stability [RSr/RSl]), and performance tests (backward medicine
ball throw [BOMB], T-run [TR], and single leg squat [SLS]).
Statistical significance was set at p # 0.05. There were
significant correlations between SLS and FLEX (r = 0.500),
LATr (r = 0.495), and LATl (r = 0.498). The TR correlated
significantly with both LATr (r = 0.383) and LATl (r = 0.448).
Of the FMS, BOMB was significantly correlated with HSr (r =
0.415), SMr (r = 0.388), PU (r = 0.407), and RSr (r = 0.391).
The TR was significantly related with HSr (r = 0.518), ILLl
(r = 0.462) and SMr (r = 0.392). The SLS only correlated
significantly with SMr (r = 0.446). There were no significant
correlations between core stability and FMS. Moderate to weak
correlations identified suggest core stability and FMS are not
strong predictors of performance. In addition, existent assess-
ments do not satisfactorily confirm the importance of core stability
on functional movement. Despite the emphasis fitness profes-
sionals have placed on functional movement and core training for
increased performance, our results suggest otherwise. Although
training for core and functional movement are important to include
in a fitness program, especially for injury prevention, they should
not be the primary emphasis of any training program.
KEY WORDS power, agility, muscle endurance
INTRODUCTION
C
ore stability is achieved through stabilization of
one’s torso, thus allowing optimal production,
transfer, and control of force and motion to the
terminal segment during an integrated kinetic
chain activity (8,14,15,23). Research has demonstrated
the importance and contributions of core stability in
human movement (12) in producing efficient trunk and
limb actions for the generation, transfer, and control of
forces or energy during integrated kinetic chain activities
(3,6,8,14,18). For example, Hodges and Richardson (12)
examined the sequence of muscle activation during whole-
body movements and found that some of the core stabilizers
(i.e., transversus abdominis, multifidus, rectus abdominis,
and oblique abdominals) were consistently activated before
any limb movements. These findings support the theory
that movement control and stability are developed in
a core-to-extremity (proximal-distal) and a cephalo-caudal
progression (head-to-toe) (8).
Functional movement is the ability to produce and
maintain a balance between mobility and stability along
the kinetic chain while performing fundamental patterns
with accuracy and efficiency (20). Muscular strength,
flexibility, endurance, coordination, balance, and move-
ment efficiency are components necessary to achieve
functional movement, which is integral to performance
and sport-related skills (8,20). Direct and quantitative
measures of functional movement are limited; however,
Cook (9) proposes qualitative assessment to gain insight
about whether abnormal movements are present, which
purportedly translate to one’s level of core stability and
how it impacts performance or injury. To determine
whether relationships truly exist between core stability
and performance, functional movement and individual
components of performance, including power, strength,
and balance, must be assessed. However, relationships
between these variables have not been established. One
explanation for the lack of evidence may be a result of the
fact that universal definitions and testing methods do not
exist (1,2,20,25,26,28). We hypothesized that there would
be a significant relationship between core stability and
functional movement and between functional movement
and performance. Also, a positive relationship would
exist between core stability and functional movement.
Address correspondence to Tomoko Okada, tokada01@gmail.com.
25(1)/252–261
Journal of Strength and Conditioning Research
� 2011 National Strength and Conditioning Association
252 Journal of Strength and Conditioning Research
the TM
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
TABLE 1. Scoring system for functional movement screen (5,6).
Tests 3 points 2 points 1 point 0 points
Deep squat Upper torso is parallel with
tibia or toward vertical.
Meet criteria of 3 points
with 2 3 6 board under
heels.
Tibia and upper torso are
not parallel.
If pain is associated with any
portion of this test.
Femur is below horizontal. Knees are not aligned
over feet.
Femur is not below horizontal.
Knees are aligned over feet. Knees are not aligned over feet.
Dowel is aligned over feet. Lumbar flexion is noted.
Hurdle step Hips, knees, and ankles
remain aligned in sagittal
plane.
Alignment lost between
hips, knees, and ankles.
Contact between foot and
hurdle occurs.
If pain is associated with any
portion of this test.
Minimal to no movement is
noted in lumbar spine.
Movement is noted in
lumbar spine.
Loss of balance is noted.
Dowel and hurdle remain
parallel.
Dowel and hurdle do not
remain parallel.
In-line lunge Minimal to no torso
movement is noted.
Movement is noted in torso. Loss of balance is noted. If pain is associated with
any portion of this test.
Feet remain in sagittal
plane on 2 3 6 board.
Feet do not remain in
sagittal plane.
Knee touches 2 3 6 board
behind heel of front foot.
Knee does not touch behind
heel of front foot.
Shoulder mobility Fists are within 1 hand
length.
Fists are within 1.5 hand
length.
Fists are not within 1.5 hand
lengths.
If pain is associated with any
portion of this test and/or
during shoulder stability screen.
Active straight-leg-raise Dowel resides between
mid-thigh and anterior
superior iliac spine.
Dowel resides between
mid-thigh and jointline
of knee.
Dowel resides below jointline. If pain is associated with any
portion of this test.
Trunk-stability push-up Males perform 1 repetition
with thumbs aligned with
top of head.
Subjects perform 1
repetition in modified
position.
Subjects are unable to perform 1
repetition in modified position.
If any pain is associated with
any portion of this test.
Females perform 1 repetition
with thumbs aligned with
chin.
Male-thumbs aligned
with chin.
If pain is noted during lumbar
extension.
Female-thumbs aligned
with chest.
Rotary stability Subjects perform 1
correct repetition while
keeping torso parallel to
board and elbow and
knee in line with board.
Subjects perform 1
correct diagonal flexion
and extension lift while
maintaining torso parallel
to board and floor.
Subjects are unable to
perform diagonal repetition.
If pain is associated with any
portion of this test.
If pain is noted during
lumbarflexion.
V
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JournalofStrength
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Therefore, the primary pur-
pose of this study was to
determine the relationships
between core stability, func-
tional movement, and perfor-
mance. A secondary purpose
of this study was to establish
which assessment tests best
represent, or correspond, with
performance.
METHODS
Experimental Approach to the
Problem
To date, relationships have not
been verified between core
stability, functional movement,
and performance. The present
study attempted to examine
whether there is a relationship
among these 3 variables in
healthy individuals. A multivariate
Figure 1. Core stability tests. A) Flexor endurance test from lateral view. B) Back extensor test from lateral view. C) Lateral musculature test from anterior
view.
Figure 2. Functional movement screen deep squat from lateral view. A) Start position. B) End position.
Figure 3. Functional movement screen core stability push-up from lateral view. A) Start position. B) End position. C) Trunk extensor test, a part of core stability
push-up test.
254 Journal of Strength and Conditioning Research
the TM
Core Stability, Functional Movement, and Performance
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
correlational design was used to
answer these study questions.
Variables were categorized as
core stability, functional move-
ment, and performance. A stan-
dard regression analysis was
used to determine whether core
stability and functional move-
ment screen (FMS) assessments
could predict performance. The
independent variables were 4
core stability tests and 12 FMS
tests. The dependent variable
was a total score from all
performance variables. Age,
height, and body mass were
used for descriptive purposes.
Figure 4. Functional movement screen hurdle step from anterior view. A) Start position. B) Mid position. C) End position.
Figure 5. Functional movement screen inline-lunge from lateral view. A) Start position. B) End position.
Figure 6. Functional movement screen shoulder mobility from posterior view. A) Measurement of length of hand with dowel. B) Performing right shoulder mobility.
C) Measurement of distance between hands with dowel.
VOLUME 25 | NUMBER 1 | JANUARY 2011 | 255
Journal of Strength and Conditioning Research
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Subjects
Twenty-eight healthy men and women (age 24.4 6 3.9 yr,
height 168.8 6 12.5 cm, mass 70.2 6 14.9 kg) were tested.
Subjects were recreational athletes from varied backgrounds
in no particular sport season. All subjects were informed of the
experimental risks and signed an informed consent document
before the investigation in addition to completing a health
history questionnaire. An individual was excluded if he/she
reported any a) somatosensory disorder that affects balance,
b) ankle instability, c) low back pain, d) lower- and upper-
extremity injuries or surgeries that resulted in time loss of
physical activity within the past year, e) current taking of
medication that affects one’s ability to maintain balance, or f )
pregnancy. This study was approved by the University
Institutional Review Board for Use of Human Subjects.
Procedures
A stopwatch (Accusplit 705X,
Accusplit, Inc., Pleasanton, CA,
USA; 0.01 s precision) was used
to measure time in seconds
during core stability tests. A
tape measure (Komelon Mea-
suring Tape 30 m Fibreglass
Closed Frame, Komelon Cor-
poration, Waukesha, WI, USA;
2 mm precision) was used to
measure distance in meters
during backward overhead
medicine ball throw (BOMB).
A 2.72 kg medicine ball (Power
Med-ball, Power Systems, Knoxville, TN, USA) was used to
assess total body power measured with BOMB. Speedtrap II
wireless timing system (Brower Timing Systems, Drape, UT,
USA; 0.01 s precision) was used to measure time in seconds
during the T-run agility test. Core muscle endurance tests
developed by McGill (17,18) was used to assess core stability.
These are composed of trunk flexor, back extensor, and right
and left lateral trunk musculature tests. The FMS developed
by Cook (8,9) was used to assess functional movement.
It consists of 7 basic human movements: deep squat (DS),
trunk-stability push-up (PU), bilateral hurdle steps (HS), in-
line lunges (ILL), shoulder mobility (SM), active straight-leg
raises (ASLR), and rotary stabilities (RS). Quality of body
movements was quantified as 0 to 3 points on the basis of
how the tasks were accomplished. The scoring system of the
each test is described in Table 1.
Subjects reported for 1 test
session that lasted approxi-
mately 2 hours. The session
was composed of screening,
familiarization, and data collec-
tion. Screening consisted of in-
formed consent, health history
questionnaire, and anthropo-
metric measurements including
height and body mass. The
dominant/stance leg was de-
termined as the leg used to
complete or recover from 2 of
the 3 tests: a balance recovery
after posterior push, a step up
onto a 20-cm step, and kicking
a ball with maximum accuracy
through a goal 10 m from the
subjects (13).
After screening, subjects
completed a warm-up that in-
cluded a light jog and both
static and dynamic stretch for
a minimum of 15 minutes or
Figure 7. Functional movement screen active straight leg raise from lateral view. A) Start position. B) End position.
Figure 8. Functional movement screen rotary stability from lateral view. A) Start position. B) Mid position. C) End
position. D) Trunk flexion test, a part of rotary stability test.
256 Journal of Strength and Conditioning Research
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Core Stability, Functional Movement, and Performance
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until they felt comfortable to perform the tests. Testing
immediately followed the warm-up. The order of the tests
was randomized among subjects to prevent fatigue and
possible test-order effects. Each test was demonstrated first
and then subjects practiced it twice to minimize learning
effects during data collection. The exception to this was
BOMB, which was familiarized with 5 practice trials, as
supported by a previous study (11).
Measurements
Core Stability Assessment. McGill’s trunk muscle endurance
tests were used to assess core stability (17,19,22,28). Results
from previous studies show that the 4 trunk isometric muscle
endurance tests have excellent reliability coefficients: trunk
flexor (FLEX), intraclass correlation coefficient (ICC) = 0.97,
back extensor (EXT), ICC = 0.97, and right and left lateral
trunk musculature (LATr/LATl), ICC = 0.99 (19). Subjects
practiced each of the body positions for a maximum of 5
seconds to avoid fatigue effects. Subjects were encouraged to
maintain the isometric postures for each test position as long
as possible (Figure 1) (17,19,22,28). The length of time
subjects could maintain the correct position was recorded.
The longest time of 2 trials, to the nearest 0.1 second, was
used for data analysis.
Functional Movement Screen. Subjects performed the FMS
by Cook (8,9). FMS tests include DS, core stability PU,
HSr/HSl, ILLr/ILLl, SMr/SMl, ASLRr/ASLRl, and
RSr/RSl (Figures 2–8) (8,9). All but DS and PU were tested
bilaterally. The FMS was shown to have an excellent
reliability coefficient (ICC = 0.98) (5). Also, it has good to
excellent intertester reliability for all of the 12 variables: ILLl,
w = 0.87; ILLr and ASLRr, w = 0.93; the other 9 variables,
w = 1.0, or perfect (21). To ensure consistency, subjects
watched a video that explained and demonstrated each of
FMS movements before being tested. Subjects performed 2
practice trialsfollowed by 3 test trials. Approximately 5
seconds of rest were given between each trial and 1 minute of
rest between each test. The subjects were instructed to return
to the initial position between each trial. Performance of each
FMS was scored according to Cook’s guidelines. The best
score in each test was used for data analysis. The order of the
tests was randomized among subjects.
Figure 9. Backward overhead medicine ball throw from lateral view. A) Preparatory phase. B) Countermovement phase. C) Upward acceleration phase. D)
Deceleration phase.
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Performance Assessments
Backward Overhead Medicine Ball Throw. The BOMB was
performed to assess total-body power (11,28). Stockbrugger
and Haennel (27) examined validity and reliability of the
BOMB explosive power test. They found that there was
a strong correlation between the distance of the medicine ball
throw and the power index for the countermovement vertical
jump (r = 0.906, p , 0.01), and the test-retest reliability of this
test was 0.996 (p , 0.01). A 2.72 kg medicine ball was used
in this study. The test consisted of 4 phases: preparatory,
countermovement, upward acceleration, and deceleration
phases (Figure 9). Each subject was given 5 practice trials
for familiarization (11) followed by 3 test trials. The distance
of the medicine ball throw was recorded (m), and the best
throw was used for the statistical analysis.
T-Run Agility Test (TR). The TR was used to assess agility and
speed (24). Previous research showed that the interclass
reliability of the TR was 0.98 when performing 3 trials (24).
Subjects ran straight forward and shuffled from left to
right and right to left and then ran straight backward on
a ‘‘T’’-shaped configuration (Figure 10). Subjects completed
2 practice trials followed by 3 test trials. Automatic sensor
TABLE 2. Summary of correlations between core stability, functional movement screen, and performance tests (n = 28).*
BOMB TR SLS
r r2 p r r2 p r r2 p
CS
FLEX 0.092 0.01 0.643 20.292 0.09 0.131 0.500† 0.00 0.007
EXT 0.052 0.00 0.794 20.188 0.04 0.337 20.063 0.00 0.748
LATr 0.152 0.02 0.441 20.383‡ 0.15 0.045 0.495† 0.25 0.007
LATl 0.167 0.03 0.397 20.448‡ 0.20 0.017 0.498† 0.25 0.007
DS 20.229 0.05 0.241 0.108 0.01 0.585 20.225 0.05 0.249
PU 0.407‡ 0.17 0.032 20.331 0.11 0.085 0.355 0.13 0.064
HSr 0.415‡ 0.17 0.028 20.518† 0.27 0.005 0.356 0.13 0.063
HSl 0.336 0.11 0.080 20.290 0.08 0.135 0.199 0.04 0.310
ILLr 0.045 0.00 0.822 20.159 0.03 0.419 0.014 0.00 0.944
FMS
ILLl 0.361 0.13 0.059 20.462‡ 0.21 0.013 0.175 0.03 0.374
SMr 20.388‡ 0.15 0.042 0.392‡ 0.15 0.039 20.446‡ 0.20 0.017
SMl 20.055 0.00 0.781 20.099 0.01 0.616 20.246 0.06 0.207
ASLRr 0.093 0.01 0.639 20.009 0.00 0.964 0.027 0.00 0.893
ASLRl 0.083 0.01 0.674 20.038 0.00 0.848 0.073 0.01 0.710
RSr 0.391‡ 0.15 0.040 20.293 0.09 0.130 0.327 0.11 0.089
RSl 0.255 0.07 0.191 20.221 0.05 0.260 0.246 0.06 0.327
*CS = core stability; FMS = functional movement screen; BOMB = backward overhead medicine ball throw; TR = T-run; SLS =
single leg squat; FLEX = flexion; EXT = extension; LATr = right lateral; LATl = left lateral; DS = deep squat; PU = core stability push-up;
HSr = right hurdle step; HSl = left hurdle step; ILLr = right in-line lunge; ILLl = left in-line lunge; SMr = right shoulder mobility; SMl = left
shoulder mobility; ASLRr = right active straight leg raise; ASLRl = left active straight leg raise; RSr = right rotary stability; RSl = left rotary
stability.
†p # 0.01.
‡p # 0.05.
Figure 10. T-run agility test.
258 Journal of Strength and Conditioning Research
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Core Stability, Functional Movement, and Performance
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timers were placed on the start/finish line. The best time, to
the nearest 0.1 second, was used for data analysis. A trial was
disqualified if the subject failed to touch either of the cones
placed right and left of the ‘‘T’’ configuration, failed to face
forward for the entire test, or failed to shuffle his or her feet (7).
Single-Leg Squat (SLS). The SLS was performed to assess
muscle endurance of the lower body. The SLS dynamic
Trendelenburg test, established by Livengood et al. (16), was
used in this study and was repeated as many times as possible
(Figure 11). This test was shown to have inter-rater reliability
with low to moderate agreement (k = 0.016–0.28) (10). Only
the dominant leg was tested for this test to reduce any fatigue
effect on the other tests. The subjects stood upright on their
dominant leg without shoes with their same-side hand on
their hip and the other hand resting on a bar for balance only.
From this position, the subjects performed a squat to approx-
imately 60� of knee flexion and returned to the initial position
and repeated it as many times as possible. One squat must
have been performed within 6 seconds, and the subjects were
instructed to maintain a hip position of 65� flexion, 10�
abduction/adduction, and the knee within 10� of valgus/
varus throughout the test (16). The test was terminated when
the subjects could not complete a squat within 6 seconds or
could not maintain proper body position. The subjects were
given 2 test trials to perform this test with approximately
5 minutes of rest between attempts. The greater number of
repetitions of the 2 trials was used for the analysis.
Statistical Analyses
Descriptive and inferential statistics were performed. Pear-
son’s product-moment correlations (r) were used to evaluate
relationships between test variables: a) core stability and
performance, b) core stability
and functional movement,
and c) functional movement
and performance. A standard
multiple regression analysis
was conducted to determine
which independent variables
in core stability and FMS were
significant predictors of total
performance. The total perfor-
mance score was calculated by
adding the SLS and BOMB
scores and subtracting the TR
score. The a-level was set at
p # 0.05.
RESULTS
There were significant correla-
tions between core stability and
performance tests (Table 2).
The SLS was positively corre-
lated with FLEX, LATr, and
LATl. The TR was negatively correlated with LATr and
LATl. Significant correlations between FMS and perfor-
mance tests were found (Table 2). The BOMB was positively
correlated with HSr, PU, and RSr but was negatively
correlated with SMr. The TR was positively related with SMr
and negatively related with HSr and SMr. The SLS was
negatively related with SMr. No significant correlations were
found between any of the core stability and FMS variables.
The multiple regression analysis included all independent
variables and indentified FLEX, LATr (core stability), and
SMr (FMS) as significant predictors of total performance.
These variables accounted for 86% of the variability in total
performance.
DISCUSSION
The primary purpose of this study was to determine the
relationships between core stability, functional movement,
and performance, and the secondary purpose was to identify
assessment tests that best predict, or represent, performance.
We assessed core stability through tests that elicited isometric
muscle contractions of the trunk musculature (17,19).
Functional movement was assessed with Cook’s FMS
(8,9). The performance tests were selected on the basis of
their required movements and muscle groups involved. The
BOMB was used to measure total-body power through
the transfer of ground forces through the legs and torso to the
upper body. The SLS was used to measure muscle endurance
of the lower body. The TR was used to measure lower-body
agility and speed.
Several significant positive (SLS vs. FLEX, LATr, and
LATl) and negative (TRvs. LATr and LATl) correlations were
identified between core stabilityand performance variables.
Figure 11. Single leg squat. A) Start position. B) End position.
VOLUME 25 | NUMBER 1 | JANUARY 2011 | 259
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The SLS had significant correlations with all of the core
stability tests except EXT. Even though SLS was used to
examine muscle endurance of the lower extremity, subjects
had to use their trunk muscles to stabilize their upper body in
an upright position. This means that the core muscles were
contracted isometrically throughout the test despite dynamic
movement of the lower extremity. Because the core stability
tests targeted isometric muscle endurance of the core, these
similarities in muscle contraction and activation types may
have resulted in their significant correlations. Next, significant
negative correlations were identified between TR and both
LATr and LATl. The LATr and LATl were established to
challenge the quadratus lumborum muscle with minimum
spine loading (19). The quadratus lumborum muscle
functions to stabilize frontal flexion and extension and resist
shearing of the spine through activation in extension, flexion,
and lateral bending (19). A good performance (i.e., faster
time) on the TR required the ability to quickly change
directions. To perform well, core stability is necessary to
withstand shear forces on the spine that occur in a multidi-
rectional task (4,7). Thus, both TR and LAT could demand
quadratus lumborum activity during the tests. Interestingly,
BOMB did not have significant correlations with any of the
core stability variables. This may be caused by the different
components tested. The core stability is used to measure
muscle endurance, whereas BOMB is used to assess
explosive power. During BOMB, the core muscles quickly
contracted to produce explosive power, so muscle endurance
does not appear to impact the task. Interestingly, EXTdid not
significantly relate to the any of the performance variables.
This appears odd because the back extensors are necessary to
help stabilize the upper body during the SLS and TR, and the
back extensors are primary movers for the BOMB.
Significant positive (BOMB vs. HSr, PU, and RSr; TR vs.
SMr) and negative (BOMB vs. SMr; TR vs. HSr and ILLl;
SLS vs. SMr) correlations were found between FMS and
performance. Possible reasons for these results may be body
coordination patterns or body movements. For example,
BOMB recruited similar body coordination and movement
patterns as HSr, RSr, and PU. The HSr was used to assess
bilateral functional mobility and stability of the hips, knees,
and ankle (8,9). Also, RSr was used to examine trunk stability
during a combined upper- and lower-extremity motion in
multiple planes (8,9). This indicates that both tests required
great total-body coordination and integration. Similarly,
stability and mobility combined with body coordination and
integration were important for better throwing distance; they
contribute to efficiently transfer the kinetic energy through
a kinetic chain and prevent an ‘‘energy leak’’ while perform-
ing the task (27). In addition, both BOMB and PU occurred
in the sagittal plane while maintaining a symmetrical body
motion. The TR also contained similar body coordination
and movement patterns as HSr and ILLl. For instance, HSr
involved a single-leg phase, and the lower-extremity move-
ments occurred in a sagittal plane while maintaining the
upper body in the upright posture. Also, ILLl demanded
mobility of the lower extremities and stability of the upper
body (8,9). Because TR consisted of running and shuffling
motions, it included single-leg stance phases and needed
mobility of the lower extremity and stability of the upper
body to accomplish the task. These similarities in body
coordination and movement patterns may have resulted in
their significant correlations. Interestingly, SMr had signif-
icant relationships with all of the performance variables.
However, the relationships are difficult to explain. All but DS
and PU were measured bilaterally. The results indicate that
significant relationships were not found bilaterally for the
majority of these variables; all except ILLl were found
significant only on the right side. This may be explained by
the dominant arms and legs of the subjects; 27 were right-
hand dominant, and 23 were right-leg dominant. This may
indicate that the majority of the subjects may have been
dominant on the right side of their bodies when performing
the tasks.
No significant relationships were found between any of the
core stability and FMS variables. Although dynamic, the FMS
requires stabilization of the core to complete the tasks for each
screen. One would believe a strong core would be necessary
to achieve each endeavor. Therefore, the lack of significant
correlations appearing between the core stability tests and
the FMS is odd. Components of the FMS, such as mobility
and coordination, may have influenced the results. This sug-
gests that, if a subject has poor mobility or coordination,
success in the FMS would not be attained despite strong core
musculature. Or, perhaps, minimum core strength is all that
is necessary to successfully complete the FMS. Overall,
the correlations between core stability and FMS and the
performance variables are difficult to explain. Similar body
movements, muscle activation, and body coordination pat-
terns are likely responsible for the results of this study.
Of the 16 variables entered into the regression model, 3
variables (FLEX, LATr, and SMr) were demonstrated as best
predictors and accounted for 86% of the variability in total
performance. The FLEX and LATr were from the core
stability category. In this study, FLEX recorded the highest
value of the 4 core stability tests. These high values are similar
to those of Tse et al. (28), who examined the improvement of
core strength in college-age rowers by using McGill’s tests. In
addition, although SMr was the only predictor from the FMS
category, it is hard to explain its prediction on performance
because no research has investigated the relationships
between SMr and total performance. However, a possible
explanation of this may be arm dominance because the
majority of the subjects were right-hand dominant. Further
study in SMr and total performance is warranted.
Although FLEX, LATr, and SMr were best predictors in
total performance, reliance on these variables (in light of the
poor correlations identified in the current study) is not
recommended. These findings are most likely caused by
different purposes of McGill’s tests and FMS with
260 Journal of Strength and Conditioning Research
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Core Stability, Functional Movement, and Performance
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performance. The McGill’s tests were developed to assess
muscle endurance of the trunk musculature in patients with
low back pain (17,19). Furthermore, FMS is used to evaluate
quality of human movements and to find deficits in the body
during dynamic movements that possibly cause injuries (8,9).
Therefore, this may suggest that low scores in the core
stability tests or FMS do not influence performance. Further
investigation is warranted to develop core stability and
functional movement assessments that correspond with
performance.
PRACTICAL APPLICATIONS
The results of this study support specificity of training. As
mentioned above, the core assessment was an isometric,
muscle endurance test, whereas the performance tests
involved dynamic movement. Therefore, it is safe to say that
isometric training of the core provided little if any benefit to
dynamic performance. Likewise, the FMS was designed to
identify potential injury in individuals, and thus it too is
ineffective in predicting performance.
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Research Article
The Bunkie Test: Descriptive Data for a Novel Test of
Core Muscular Endurance
Jason Brumitt
George Fox University, 414 N. Meridian Street, #V123, Newberg, OR 97132, USA
Correspondence should be addressed to Jason Brumitt; jbrumitt@georgefox.edu
Received 30 September 2014; Accepted 7 January 2015
Academic Editor: Francois Prince
Copyright © 2015 Jason Brumitt.This is an open access article distributed under the Creative CommonsAttribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The Bunkie test, a functional performance test consisting of 5 test positions (performed bilaterally), has been used to assess aspects
of muscular function. Current performance measures are based on clinical recommendations. The purpose of this study was to
report normative data for a healthy population. One hundred and twelve subjects (mean age 25.9±4.5 years) were recruited from a
university setting. Subjects completed a demographic questionnaire prior to testing. Hold times for each position was measured in
seconds. Subjects were able to hold many of the positions for a mean score of approximately 40 seconds.There were no side-to-side
differences in test position hold times per gender. Males were able to hold some positions significantly longer than their female
counterparts. Males with a lower BMI were able to hold 8 of the 10 positions significantly longer than those with a higher BMI.
Bunkie test scores in subjects with a prior history of musculoskeletal injury were similar to those with no history of injury. The
normative data presented in this study may be used by rehabilitation professionals when assessing and rehabilitating their patients.
1. Introduction
Rehabilitation professionals assess muscular endurance and
strength in patients and clients utilizing a variety of tests and
measures (e.g., manual muscle tests, functional performance
tests, dynamometry, and isokinetic testing). Functional per-
formance tests (FPTs) “simulate sport and activity” assess-
ing aspects of performance, functional abilities, and/or the
presence of dysfunctional movement patterns [1, 2]. FPTs
(also known as functional tests) have gained popularity for
assessing risk of injury, identifying dysfunction, tracking
progress during a rehabilitation program, and clearing an
athlete to return to sport [3–7]. Rehabilitation professionals
utilize FPTs to assess muscular endurance or strength in
patients and clients that cannot be easily assessed with other
clinical tests [2, 8, 9].
Assessing muscular endurance of the core (e.g., lum-
bopelvic musculature) is frequently performed by having a
patient or client assume a static posture recording how long
one can maintain the position. McGill et al. have described
three FPTs to assess muscular endurance capacity of the core:
the lateral musculature test (performed bilaterally), the flexor
endurance test, and the back extensors test [10, 11]. Each
test is timed to identify one’s muscular endurance capacity.
The relationship between test scores is calculated to identify
individuals who may be at risk for a low back injury [11].
Schellenberget al. reported mean hold durations for the
prone and supine bridge tests in asymptomatic individuals
and those with low back pain (LBP) [12]. Asymptomatic
subjects were able to hold the prone bridge (72.5 ± 32.6 s)
and the supine bridge (170.4± 42.5 s) significantly longer than
those with LBP (prone bridge = 28.3 ± 26.8 s; supine bridge
76.7 ± 48.9 s) [12]. The FPT scores for the core musculature
are used by rehabilitation professionals to guide therapeutic
exercise prescription [11, 13].
de Witt and Venter have proposed a FPT consisting of 5
test positions (each test performed bilaterally for a total of 10
tests) which requires the subject to assume plank or modified
plank postures with one’s lower extremities supported on a
bench [14].This FPT has been coined the Bunkie test, derived
from “bankie” the Afrikaans word for a little bench [14].
de Witt and Venter suggest that endurance athletes should
be able to hold each test position for up to 40 s [14]. The
aforementioned value represents a clinical recommendation
by de Witt and Venter [14]; however, normative values for a
general population are currently unknown.
Hindawi Publishing Corporation
Rehabilitation Research and Practice
Volume 2015, Article ID 780127, 9 pages
http://dx.doi.org/10.1155/2015/780127
http://dx.doi.org/10.1155/2015/780127
2 Rehabilitation Research and Practice
The purpose of this investigation was to present norma-
tive data for the Bunkie test in a healthy, general (noncompet-
itive athlete) population. It was hypothesized that therewould
be no statistical difference in Bunkie test scores between sides
(e.g., right side versus left side) within each gender group,
between genders, or per demographic characteristic. It was
also hypothesized that there would be a statistical difference
in scores based on history of musculoskeletal injury.
2. Materials and Methods
2.1. Subjects. One hundred and twelve subjects (81 females,
mean age 25.9 ± 4.4 y; 31 males, mean age 26.1 ± 4.7 y)
were recruited from a university graduate school setting.
Subjects were recruited to participate in the study either
via direct invitation or via recruitment flyers distributed
throughout the university. A subject was excluded from
testing if she/hewas under the age of 18, was a female whowas
pregnant, was currently experiencing musculoskeletal pain,
or was currently receiving treatment for musculoskeletal
symptoms from a licensedmedical professional (e.g., medical
doctor or other primary care provider, physical therapist,
or chiropractor). The Institutional Review Board of Pacific
University (Forest Grove, OR) approved this study.
Each subject completed a brief questionnaire collecting
demographic information including age, gender, previous
injuries to the extremities that required medical care (from a
primary provider or allied health care provider), and previous
injuries to the spine or pelvis that requiredmedical care (from
either a primary provider or allied health care provider).
Height (to nearest half inch) and weight (to nearest half
pound) were recorded using a standard medical scale.
2.2. Procedure. The Bunkie test consists of 5 testing positions
with each test performed bilaterally (Figures 1–5). Order of
testing was randomized per each subject. A roll of a die
determined order of testing (roll of 1 = anterior power line
(APL); 2 = lateral stabilizing line (LSL); 3 = posterior power
line (PPL); 4 = posterior stabilizing line (PSL); 5 = medial
stabilizing line (MSL); 6 = roll again). Sequencing of the
remaining tests was based on the initial number rolled. For
example, a subject who rolled a 4 would perform the PSL first
with the remaining tests performed sequentially (5, 1, 2, 3).
A flip of a coin was performed to determine which side was
tested first.
Subjects were shown a picture of each test (see Figures
1–5) and asked to assume the test position with their upper
extremities placed against a floor mat and the lower extrem-
ities (LE) positioned (approximately mid-Achilles) on the
treatment table. The height between the top of the mat and
the treatment table top was standardized at 30 cm. Once in
position, the primary investigator (PI) provided verbal cues
to help facilitate the correct posture prior to initiating the test.
The PI next instructed the subject to elevate one LE off of
the surface of the treatment table. For this study, when the
right LE was weight-bearing on the treatment table it was
described as a right sided test. The time that one was able
to maintain the proper test position was recorded in seconds
using a stopwatch. A test was terminated when a subject was
Figure 1: Anterior power line (APL).
Figure 2: Lateral stabilizing line (LSL).
no longer able to maintain the proper test position (as shown
in Figures 1–5). Examples of test termination occurred when
either (a) the subject stopped the test due to fatigue or (b) the
subject was unable to maintain the correct position. Subjects
were allowed one attempt to correct their position; if they
were unable to assume the correct posture after verbal cueing
the test was stopped. Thirty seconds of rest was allowed
between tests.
2.3. Statistical Analysis. Means (±SD)were calculated for age,
height, weight, BMI, and hold times for each Bunkie test
position. Independent 𝑡-tests were calculated to assess for
differences in hold times between lower extremities for each
group (all subjects, females, males). Independent t-tests were
calculated to assess for differences in test scores based on
demographic characteristics: mean age, mean BMI, and prior
history of musculoskeletal injury. Independent t-tests were
also calculated to assess for differences in Bunkie test position
hold times between genders. Data analyses were performed
using SPSS 17.0 with alpha level set at 0.05.
3. Results and Discussion
The test-retest reliability for each positionwas calculated dur-
ing a pilot study prior to subject recruitment. The intraclass
correlation coefficients (ICC
3,1
) were as follows: APLwas 0.82
(95% CI: 0.67, 0.94); LSL was 0.95 (95% CI: 0.90, 0.98); PPL
was 0.95 (95% CI: 0.90, 0.98), PSL was 0.92 (95% CI: 0.84,
0.97), and the MSL was 0.95 (95% CI: 0.90, 0.98).
Rehabilitation Research and Practice 3
Table 1: Demographic characteristics (mean ± SD).
Characteristic Total
(𝑛 = 112)
Females
(𝑛 = 81)
Males
(𝑛 = 31)
Age (y) 25.9 (4.5) 25.9 (4.4) 26.1 (4.7)
Height (m) 1.69 (.09) 1.66 (.06) 1.79 (.07)
Weight (kg) 66.8 (12.5) 61.2 (6.8) 81.3 (12.3)
BMI (kg/m2) 23.2 (3.0) 22.3 (2.3) 25.5 (3.4)
Prior history of musculoskeletal injury
(prior history of injury/total𝑁) 73/112 53/81 20/31
Prior history of back injury
(prior history of injury/total𝑁) 25/112 21/81 4/31
Figure 3: Posterior power line (PPL).
Figure 4: Posterior stabilizing line (PSL).
Figure 5: Medial stabilizing line (MSL).
Demographic information of the study sample is pre-
sented in Table 1. Eighty-one of the 112 subjects were female.
Fifty-three of the 81 female subjects (65 percent) reported a
prior history of musculoskeletal injury that required evalua-
tion and treatment by a medical professional. Twenty-one of
the 81 female subjects (26 percent) reported history of back
(thoracic or lumbar region) injury that required evaluation
and treatment by a medical professional. Sixty-four percent
(20 out of 31) of male subjects reported prior history of
musculoskeletal injury requiring medical treatment. Only 13
percent (4 out of 31) of male subjects reported prior history
of back (thoracic or lumbar region) injury.
Mean (± SD) Bunkie scores for the 5 tests (10 positions)
are presented in Table 2. “All subjects” (e.g., both female and
male subjects) were able to hold 4 of the test positions for
at least a minimum of 40 s (mean score): APL (L), LSL (R),
PPL (R), and PPL (L). Mean scores for 4 other test positions,
APL (R), LSL (L), PSL (R), and PSL (L), were very close
to 40 s. The mean hold times for the MSL tests (R = 23.6
(±15.0) s; L = 22.2 (±13.9) s) were shorter in duration when
compared to allanalysis of
variance) between curl-up exercises. CU5curl-up on stable bench (task A); CUBF5curl-up with the upper body over a labile gym ball and with both feet flat on
the floor (task B); CUBB5curl-up with the upper body over a labile gym ball and with both feet on a bench (task C); CUPT5curl-up with the upper body
supported by a labile wobble board (task D); URAR5upper portion of rectus abdominis muscle, right side; LRAR5lower portion of rectus abdominis muscle, right
side; URAL5upper portion of rectus abdominis muscle, left side; LRAL5lower portion of rectus abdominis muscle, left side; OER5external oblique muscle, right
side; OIR5internal oblique muscle, right side; OEL5external oblique muscle, left side; OIL5internal oblique muscle, left side.
Figure 2.
Amplitudes of right-side muscle pairs expressed as a ratio. CU5curl-up
on stable bench (task A); CUBF5curl-up with the upper body over a
labile gym ball and with both feet flat on the floor (task B); CUBB5curl-up
with the upper body over a labile gym ball and with both feet on a bench
(task C); CUPT5curl-up with the upper body supported by a labile
wobble board (task D); URAR5upper portion of rectus abdominis
muscle, right side; LRAR5lower portion of rectus abdominis muscle,
right side; OER5external oblique muscle, right side; OIR5internal
oblique muscle, right side.
Figure 3.
Amplitudes of left-side muscle pairs expressed as a ratio. CU5curl-up on
stable bench (task A); CUBF5curl-up with the upper body over a labile
gym ball and with both feet flat on the floor (task B); CUBB5curl-up with
the upper body over a labile gym ball and with both feet on a bench
(task C); CUPT5curl-up with the upper body supported by a labile
wobble board (task D); URAL5upper portion of rectus abdominis
muscle, left side; LRAL5lower portion of rectus abdominis muscle, left
side; OEL5external oblique muscle, left side; OIL5internal oblique
muscle, left side.
568 . Vera-Garcia et al Physical Therapy . Volume 80 . Number 6 . June 2000
muscle activity we obtained compare well with the data
of Axler and McGill,7 who noted that generally curl-ups
(at least on stable surfaces) were the safest of those
chosen from a wide variety of abdominal muscle exer-
cises. The activity levels observed in the current study
(from approximately 20% to 55% of MVC in the rectus
abdominis muscle) appear to constitute stimuli to
increase both force production (strength) and endur-
ance properties of muscle. Furthermore, the activity
levels in the obliques observed in the labile curl-up tasks
of our study (ie, from 5% to 20% of MVC in the oblique
muscles) suggest a generous margin to ensure “sufficient
stability” in a spine positioned in a neutral posture.2,10
Sarti et al3 also attempted to address the issue of whether
an individual can preferentially the recruit the upper or
lower section of the rectus abdominis muscle. Their data
suggested that some highly trained individuals were able
to preferentially recruit the lower section of the rectus
abdominis muscle during specific maneuvers executed
during supine lying where the legs and pelvis were raised
from the floor. Our data make it difficult to make a
conclusive statement on this issue because there were
slight postural changes among the 4 tasks and particu-
larly between the 2 tasks that suggested a differential of
20% of MVC between the upper and lower portions of
the rectus abdominis muscle.
Interpretation of the data in our study is limited because
our subjects were relatively physically fit. Future investi-
gations should include patients with different spinal
conditions, of different ages, and so on. Furthermore, the
tasks of this study involved holding positions, and there is
no doubt that motion would change muscle activity levels.
Finally, our tasks were designed to be nonfatiguing, and
fatiguing conditions may lead to different results.
Conclusion
Performing curl-ups on labile surfaces changes both the
muscle activity amplitude and the way that the muscles
coactivate to stabilize both the spine and the whole body.
This finding suggests a much higher demand on the
motor system, which may be desirable for specific stages
in a rehabilitation program as long as the concomitant
higher spine loads are tolerable.
References
1 McGill SM. Low back exercises: evidence for improving exercise
regimens. Phys Ther. 1998;78:754–765.
2 Cholewicki J, McGill SM. Mechanical stability of the in vivo lumbar
spine: implications for injury and chronic low back pain. Clin Biomech.
1996;11:1–15.
3 Sarti MA, Monfort M, Fuster MA, Villaplana LA. Muscle activity in
upper and lower rectus abdominus during abdominal exercises. Arch
Phys Med Rehabil. 1996;77:1293–1297.
4 Monfort M, Lison JF, Lopez E, Sarti A. Trunk muscles and spine
stability [abstract]. European Journal of Anatomy. 1997;1:52.
5 McGill SM, Sharratt MT, Seguin JP. Loads on spinal tissues during
simultaneous lifting and ventilatory challenge. Ergonomics.
1995;38:1772–1792.
6 Juker D, McGill SM, Kropf P, Steffen T. Quantitative intramuscular
myoelectric activity of lumbar portions of psoas and the abdominal wall
during a wide variety of tasks. Med Sci Sports Exerc. 1998;30:301–310.
7 Axler C, McGill SM. Low back loads over a variety of abdominal
exercises: searching for the safest abdominal challenge. Med Sci Sports
Exerc. 1997;29:804–811.
8 McGill SM. Low back exercises: prescription for the healthy back and
when recovering from injury. In: American College of Sports Medicine
Resource Manual for Guidelines for Exercise Testing and Prescription. 3rd ed.
Baltimore, Md: Williams & Wilkins, 1998:116–128.
9 McGill SM. Electromyographic activity of the abdominal and low
back musculature during the generation of isometric and dynamic
axial trunk torque: implications for lumbar mechanics. J Orthop Res.
1991;9:91–103.
10 Cholewicki J, Panjabi MM, Khachatryan A. Stabilizing function of
trunk flexor-extensor muscles around a neutral spine posture. Spine.
1997;22:2207–2212.
Figure 4.
Amplitudes of the upper and lower portions of the rectus abdominis
muscle expressed as a ratio. CU5curl-up on stable bench (task A);
CUBF5curl-up with the upper body over a labile gym ball and with both
feet flat on the floor (task B); CUBB5curl-up with the upper body over a
labile gym ball and with both feet on a bench (task C); CUPT5curl-up
with the upper body supported by a labile wobble board (task D);
URAR5upper portion of rectus abdominis muscle, right side;
LRAR5lower portion of rectus abdominis muscle, right side;
URAL5upper portion of rectus abdominis muscle, left side; LRAL5lower
portion of rectus abdominis muscle, left side.
Physical Therapy . Volume 80 . Number 6 . June 2000 Vera-Garcia et al . 569
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ARTIGO ORIGINAL
ISSN: 2178-7514
Vol. 7 | Nº. 1| Ano 2015
AVALIAÇÃO INDIRETA DA FORÇA DOS MÚSCULOS DO CORE 
EM INICIANTES DE ACADEMIA
Evaluation of core muscles strength in beginners of the resistance training
Marcia Aurora Soriano Reis1, Mauro Antonio Guiselini2; Priscyla Silva Monteiro Nardi3, 
Guanis de Barros Vilela Junior1; Paulo Henrique Marchetti1,2,3
RESUMO
O objetivo deste estudo foi avaliar e classificar o nível de força de forma indireta os músculos do 
core em indivíduos ingressantes de academia baseados na proposta de avaliação de Kendall. A 
amostra foi composta por 1317 alunos ingressantes de uma academia de ginástica de São Paulo, 
submetidos a uma bateria de testes de avaliação física, sendo 536 do sexo masculino e 781 do sexo 
feminino, agrupados por faixas etárias entre 20 a 29 anos, 30 a 39 anos, 40 a 49 anos e 50 a 59 anos. 
Foram realizadas análises de percentual, onde o grupo total de sujeitos foi separado em diferentes 
amostras como gênero e idade, e comparados em relação ao percentual total dos escores obtidos no 
teste. Conclui-se que a grande maioria dos indivíduos não apresenta um grau adequado de força e 
estabilidade do core baseados na proposta de avaliação de Kendall. 
Palavras-chave: biomecânica, treinamento, desempenho.other test positions. There were no side-to-
side differences between extremities for the total population.
Female subjects were able to hold three test positions
for a mean score of a minimum of 40 s (mean score): LSL
(R), PPL (R), and the PPL (L) (Table 2). Females held the
MSL position for the shortest time period (R = 21.3 (±15.5) s;
L = 20.3 (±13.9) s). Female subjects were able to hold the PPL
for the longest time period (R = 46.9 (±21.6) s; L = 50.3
(±24.6) s). There were no side-to-side differences between
lower extremities for each test position in this group.
Male subjects were able to hold five test positions for
a minimum of 40 s (mean score): APL (R), APL (L), LSL
(R), PPL (R), and the PPL (L) (Table 2). Males held the
MSL position for the shortest time period (R = 29.8 (±11.9) s;
L = 27.0 (±13.1) s). Male subjects were able to hold the PPL
for the longest time period (R = 46.3 (±23.7) s; L = 46.5
(±31.4) s). There were no side-to-side differences between
lower extremities for each test position in this group.
Male subjects held three of the test positions significantly
longer than their female counterparts.Maleswere able to hold
the APL (L) position for 45.5 (±17.5) s whereas females were
only able to hold this test position 37.9 (±14.2) s (𝑃 = 0.02)
(Table 2). Males were also able to hold eachMSL test position
(R = 29.8 (±11.9) s; L = 27.0 (±13.1) s) significantly longer than
4 Rehabilitation Research and Practice
Table 2: Bunkie test scores (mean ± SD) and comparisons between female and male subjects.
Bunkie test
position
(seconds)
Total
(𝑛 = 112) 𝑃 value∗ Females
(𝑛 = 81) 𝑃 value∗ Males
(𝑛 = 31) 𝑃 value∗
Between gender
differences
𝑃 value∗
APL
R 38.6 (16.3) 0.5 36.9 (16.7) 0.7 42.9 (14.5) 0.5 0.09
L 40.0 (15.5) 37.9 (14.2) 45.5 (17.5) 0.02
LSL
R 42.0 (18.8) 0.3 41.9 (20.4) 0.5 42.1 (14.1) 0.3 0.9
L 39.5 (17.9) 39.9 (19.4) 38.6 (13.5) 0.7
PPL
R 46.7 (22.1) 0.4 46.9 (21.6) 0.3 46.3 (23.7) 0.9 0.9
L 49.2 (26.6) 50.3 (24.6) 46.5 (31.4) 0.5
PSL
R 38.6 (17.3) 0.9 38.7 (17.3) 0.9 38.1 (17.5) 0.7 0.9
L 38.4 (17.6) 39.0 (17.4) 36.7 (18.0) 0.5
MSL
R 23.6 (15.0) 0.4 21.3 (15.5) 0.7 29.8 (11.9) 0.4 0.007
L 22.2 (13.9) 20.3 (13.9) 27.0 (13.1) 0.02
∗Independent t-tests.
APL = anterior power line; LSL = lateral stabilizing line; PPL = posterior power line; PSL = posterior stabilizing line; MSL = medial stabilizing line.
their female counterparts (R = 21.3 (±15.5) s, 𝑃 = 0.007; L =
20.3 (±13.9) s, 𝑃 = 0.02).
Table 3 presents Bunkie test scores for “all subjects” based
on age, BMI, and prior history of injury. Age and BMI were
categorized by this study’s population mean scores. There
were no significant differences between Bunkie test scores
based on one’s age. There were two significant findings based
on BMI. Those with a lower BMI ((14
.1)
0.
9
25
.3
(1
2.
9)
22
.1
(1
6.
8)
0.
3
23
.0
(1
6.
0)
24
.7
(1
3.
2)
0.
6
19
.2
(1
3.
2)
24
.9
(1
5.
4)
0.
1
L
22
.0
(14
.4
)
22
.6
(1
3.
1)
0.
8
23
.7
(1
2.
0)
20
.7
(1
5.
6)
0.
3
22
.6
(14
.8
)
21
.3
(1
2.
2)
0.
7
20
.4
(1
2.
9)
22
.7
(14
.2
)
0.
5
∗
In
de
pe
nd
en
tt
-te
sts
.
A
PL
=
an
te
rio
rp
ow
er
lin
e;
LS
L
=
lat
er
al
sta
bi
liz
in
g
lin
e;
PP
L
=
po
ste
rio
rp
ow
er
lin
e;
PS
L
=
po
ste
rio
rs
ta
bi
liz
in
g
lin
e;
M
SL
=
m
ed
ia
ls
ta
bi
liz
in
g
lin
e.
6 Rehabilitation Research and Practice
Ta
bl
e
4:
Bu
nk
ie
te
st
sc
or
es
(m
ea
n
±
SD
)f
or
fe
m
al
es
ub
je
ct
s(
𝑛
=
8
1
)b
as
ed
on
ag
e,
BM
I,
an
d
pr
io
rh
ist
or
y
of
in
ju
ry
.
Bu
nk
ie
te
st
po
sit
io
n
(s
ec
on
ds
)
A
ge
asymmetrical hold times that correlated
with left-sided weakness of the gluteus maximus, gluteus
medius, and hip external rotators (as assessed by traditional
manual muscle testing) [16]. The prescription of therapeutic
exercises targeting core muscular weakness improved the
patient’s ability to activate her gluteal muscles. At her follow-
up visit 8 days later she was able to hold the Bunkie test
positions for longer periods and return to running pain-free.
One other study to date has reported mean scores for the
Bunkie test. van Pletzen and Venter reported Bunkie scores
in 121 elite-level rugby union athletes [17]. Mean scores for
front row rugby players ranged from the lowest score of 21.51
(±12.56) s for the medial stabilizing line (left side) to the
highest score of 35.63 (±9.21) s for the anterior power line
(right side). Mean scores for backline rugby players range
from the lowest score of 27.96 (±13.77) s for the posterior
stabilizing line (left side) to the highest score of 39.87 (±0.66) s
for the anterior power line (right side). vanPletzen andVenter
[17] utilized a similar testing protocol as that described by de
Witt and Venter [14] having the rugby player hold the test
position up to amaximumof 40 s.Despite the time restriction
and test termination requirement based on musculoskeletal
sensations, the subjects in van Pletzen and Venter [17]
held the tests for similar time periods as subjects in this
study.
Future investigations are warranted to determine the
utility of the Bunkie test. Descriptive studies are warranted to
identify normative data in injured populations (e.g., chronic
low back). In this study subjects with a prior history of
injury did not demonstrate significant differences in hold
times when compared to individuals with no history of
injury. However, for an injured patient the Bunkie test
may be clinically useful as a test to identify asymmetry
of muscular endurance or as a tool to track increases in
muscular function during a course of rehabilitation [16].
Clinicians should utilize caution and their clinical judgment
when assessing the injured patient. The Bunkie test may be
too aggressive for patients who are in the acute stage of
healing; however, those who are in subacute or chronic stages
may be able to tolerate the test without symptomprovocation.
The Bunkie test should also be evaluated for its ability to
identify individuals who may be at risk for a future injury
(e.g., endurance athletes, manual laborers). For example, the
test should be administered to a cohort of athletes at the
start of the season with scores assessed at the end of the
season to determine if associations exist between time-loss
injuries and preseason performance. Finally, aspects of the
testing protocol warrant further assessment. In this study, the
height of the table top to the floor was standardized for all
subjects to 30 cm. de Witt and Venter [14] recommended a
range of 25 to 30 cm depending on individual size; however,
no guidance was provided as to a how to set the Bunkie
floor-to-bench height based on an individual’s height. In
this study subjects were allowed 30 seconds of rest between
each test. The 30 s time period was selected to replicate how
some FPTs are administered clinically [2]. What length of
rest should be allowed to optimize recovery is yet to be
determined.
4. Conclusion
This investigation presents normative data for the Bunkie test
in healthy individuals. Subjects in this study were able to
hold many of the positions for a mean score of approximately
40 seconds. There were no side-to-side differences in test
position hold times per gender. For the most part, Bunkie
test scores were similar between those with prior history of
musculoskeletal injury and those with no prior history. This
normative data may be useful for rehabilitation professionals
when comparing their patient’s or client’s Bunkie test scores
to a general population.
Rehabilitation Research and Practice 9
Conflict of Interests
The author declares that there is no conflict of interests
regarding the publication of this paper.
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International Journal of Sports Science and Coaching, vol. 7, no.
3, pp. 545–556, 2012.
To Crunch or Not to
Crunch: An Evidence-
Based Examination of
Spinal Flexion Exercises,
Their Potential Risks, and
Their Applicability to
Program Design
Bret Contreras, MA, CSCS1and Brad Schoenfeld, MSc, CSCS2
1Auckland University of Technology, Auckland, New Zealand; and 2Global Fitness Services, Scarsdale, New York
S U M M A R Y
THE CRUNCH AND ITS MANY VAR-
IATIONS HAVE LONG BEEN CON-
SIDERED A STAPLE EXERCISE IN
FITNESS PROGRAMS. HOWEVER,
RECENTLY, SOME FITNESS PRO-
FESSIONALS HAVE QUESTIONED
THE WISDOM OF PERFORMING
FLEXION-BASED SPINAL EXER-
CISES, SUCH AS THE CRUNCH.
CONCERNS ARE USUALLY PREDI-
CATED ON THE BELIEF THAT THE
SPINE HAS A FINITE NUMBER OF
BENDING CYCLES AND THAT EX-
CEEDING THIS LIMIT WILL HASTEN
THE ONSET OF VERTEBRAL DE-
GENERATION. THIS ARTICLE WILL
SEEK TO REVIEW THE RESEARCH
PERTAINING TO THE RISKS OF
PERFORMING DYNAMIC SPINAL
FLEXION EXERCISES AND WILL
DISCUSS THE APPLICATION OF
THESE FINDINGS TO EXERCISE
PERFORMANCE.
T
he crunch and its many varia-
tions have long been consid-
ered a staple exercise in fitness
programs. These exercises involve
dynamic flexion of the spine in the
sagittal plane and are performed to
increase abdominal strength and de-
velopment (124), particularly in the
rectus abdominis and obliques mus-
culature. Strength and conditioning
coaches frequently include such exer-
cises as a component of athletic
routines designed to enhance sporting
performance (45).
Recently, however, some fitness pro-
fessionals have questioned the wisdom
of performing flexion-based spinal ex-
ercises, such as the crunch (23,75,110).
Concerns are usually predicated on the
belief that the spine has a finite number
of bending cycles and that exceeding
this limit will hasten the onset of disc
damage (75). Proponents of the theory
claim that spinal flexion therefore
should be saved for activities of daily
living such as tying one’s shoes rather
than ‘‘wasted’’ on crunches and other
flexion-based abdominal exercises. Op-
ponents of the theory counter that an
alarming discrepancy exists between
laboratory results and what is occur-
ring in gyms and athletic facilities
around the world with respect to total
flexion cycles and spinal injury and cite
a lack of evidence showing any detri-
ments. Therefore, the purpose of this
article will be 3-fold: First, to review
the relevant research pertaining to the
risks of performing dynamic spinal
flexion exercises; second, to explore
the potential benefits associated with
spinal flexion exercises; and third, to
discuss the application of these findings
to exercise program design.
K E Y W O R D S :
spinal flexion; crunch; trunk flexion;
spinal biomechanics
VOLUME 33 | NUMBER 4 | AUGUST 2011 Copyright � National Strength and Conditioning Association8
OVERVIEW OF DEGENERATIVE
DISC DISEASE
The intervertebral discs form cartilagi-
nous joints between adjacent vertebrae,
which stabilize the spine by anchoring
the vertebrae to one another. The discs
also facilitate multiplanar spinal move-
ment and help absorb vertebral shock.
Discs have 3 distinct portions: an outer
layer annular fibrosus, a central nucleus
pulposus, and 2 hyaline cartilage end
plates (64). The annulus, which has an
inner and outer component, consists of
multiple layers of fibrocartilage, primar-
ily a combination of type I and type II
collagen (39). The annulus serves to
resist outward pressure, also known as
tensile or hoop stresses, during axial
compression and to stabilize the verte-
bral joint during motion (138). The
annulus also serves to contain the inner
nucleus, which is a gel-like structure
composed of a mixture of chondrocytes,
collagen, elastin, and proteoglycans
(130). Proteoglycans serve to resist
compressive loading because of their
glycosaminoglycan (GAGs) content
(114). Glycosaminoglycans are long-
branch polysaccharides that attract
and bind to water and provide osmotic
pressure. The nucleus functions as
a ‘‘water pillow,’’ helping to cushion
the vertebrae from axial loads and
distribute pressures uniformly over ad-
jacent vertebral end plates (111). The
end plates contain primarily type II
collagen (55), are less than 1 mm thick,
and contain fibers that extend into the
disc (138). In addition to preventing the
nucleus from protruding into adjacent
vertebrae, the end plates also help to
absorb hydrostatic pressure caused by
spinal loading (26,81) and allow for
nutrient diffusion (131).
Degenerative disc disease is a multifac-
torial process involving genetic, me-
chanical, biological, and environmental
factors (59). The first common signs of
disc degeneration often appear between
11 and 16 years of age, with approxi-
mately 20% of teenagers displaying mild
disc degeneration (79). However, minor
signs of degeneration, such as mild cleft
formation and granular changes to the
nucleus, appear in disc of 2 year olds
(21). Discs tend to progressively de-
teriorate with age, with a majority of
discs showing signs of degeneration by
the time a person is 70 years old (79).
Age-related degeneration involves a re-
duction in proteoglycan and collagen
levels (114), a 5-fold reduction in the
fixed charge density (a measure of
mechanoelectrochemical strength) of
GAGs in the nucleus (60), and a 2-fold
decrease in hydration between adoles-
cent discs and discs of 80 year olds
(129), which diminishes the disc’s
height and load-bearing capabilities
(8,22). Men tend to exhibit more disc
degeneration than women, which is
thought to be because of a combination
of increased trunk strength, increased
resistance lever arms that heighten
spinal forces and stresses, increased
heavy loading, and increased distance
for nutrient travel (79).
Intervertebral disc degeneration can
manifest from a structural disturbance
in the annulus, nucleus, or end plate (7).
Aging, apoptosis, collagen abnormalities,
vascular ingrowth, mechanical loading,
and proteoglycan abnormalities can all
contribute to disc degeneration (71). As
discs degenerate, focal defects arise in the
cartilage end plate, the nuclei become
increasingly more consolidated and fi-
brous, and the number of layers in the
annulus diminishes (119). This has been
shown to alter disc height, spinal bio-
mechanics, and load-bearing capabilities
(99) and ultimately can lead to spinal
stenosis—an advanced form of degener-
ative disc disease that causes compres-
sion of the contents of the spinal canal,
particularly the neural structures (93).
End plate calcification also contributes to
disc degeneration by decreasing nutrient
diffusion that interferes with the pH
balance and increases inflammatory
responses in the nucleus (34). Yet despite
a clear association between degenerative
spinal changes and an increased in-
cidence of lower back pain (LBP) (65),
many afflicted individuals are neverthe-
less asymptomatic (19,20,139).
DOES SPINAL FLEXION CAUSE
DISC INJURY?
A variety of research approaches
have been used to elucidate spinal
biomechanics and their impact on disc
pathophysiology, including the use of
animal and human in vivo (i.e., within
the living) models, animal and human
in vitro models (i.e., within the glass),
and computer-based in silico models
(63). In particular, in vitro research has
implicated repetitive lumbar flexion as
the primary mechanism of disc herni-
ation (protrusion of disc material
beyond the confines of the annular
lining) and prolapse (a bulging of
nucleus pulposus through annulus
fibrosus) because evidence shows that
these pathologies proceed progres-
sively from the inside outward through
nuclear migration toward the weakest
region of the annulus, the posterolat-
eral portion (62,127).
Most in vitro studies on spinal bio-
mechanics that are applicable to
the crunch exercise have used cervi-
cal porcine models (30,35,36,70,123).
These models involve mounting spinal
motion segments in custom appara-
tuses that apply continuous compres-
sive loads combined with dynamic
flexion and extension moments. Total
bending cycles have ranged from 4,400
to 86,400, with compression loads
equating to approximately 1,500 N.
Considering that Axler and McGill
(13) found that a basic crunch varia-
tion elicited around 2,000 N of com-
pression, the amount of compressionin
the various studies is reasonable for
making comparisons with the crunch
exercise. In each of the aforementioned
studies, a majority of the discs experi-
enced either complete or partial her-
niations, particularly to the posterior
annulus. This suggests a cause-effect
relationship between spinal flexion and
disc damage. The results of the studies
are summarized in the Table.
Although the aforementioned studies
seem to lend credence to the potential
risks of repeated spinal bending, there
are several issues with attempting to
extrapolate conclusions from a labora-
tory setting to the gym. First and
foremost, the studies in question were
performed in vitro, which is limited by
the removal of musculature and does
not replicate the in vivo response to the
Strength and Conditioning Journal | www.nsca-lift.org 9
human spine during normal movement
(98,141–143,147). As with all living
tissue, the vertebrae and its supporting
structures remodel when subjected to
applied stress (24). Consistent with
Wolff’s and Davis’s Laws, deformation
of cellular tissues are met by a corre-
sponding increase in the stiffness of the
matrix, which in turn helps to resist
future deformation (102,103). The
vertebrae and intervertebral discs are
no exception because they have been
shown to adaptively strengthen when
exposed to progressive exercise
(2,24,66,92). Cadaveric tissue does
not have the capacity to remodel.
Another important point to consider
when interpreting results of in vitro
studies involving cyclic spinal loading
is that natural fluid flow is compro-
mised. Van der Veen et al. (132) found
that although porcine lumbar motion
segments showed outflow of fluid dur-
ing loading, inflow failed to occur dur-
ing unloading, thereby decreasing
disc height and interfering with normal
disc biomechanics.
In vitro comparisons are further com-
plicated by the use of animal models.
Although animal models do have
structural similarities to the human
spine (146,29), especially the porcine
cervical spine in comparison with the
human lumbar spine, numerous ana-
tomical and physiological variations
nevertheless exist (130). Of particular,
relevance to flexion studies is the fact
that the absolute ranges of motion are
smaller in porcine subjects compared
with humans (10). These variations are
most prominent in flexion and exten-
sion, which may mitigate the ability to
draw applicable conclusions to human
dynamic spinal exercise.
Furthermore, the studies in question
attempted to mimic loading patterns of
occupational workers by subjecting spi-
nal segments to thousands of continuous
bending cycles, which is far beyond what
is normally performed in the course of
a dynamic exercise program. Typical
core strengthening routines use a limited
number of dynamic repetitions, and on
completion of a set, trainees then rest for
a given period before performing an-
other set. Thus, total bending cycles per
session ultimately amount to a fraction of
those used in the cited research proto-
cols, and these cycles are performed
intermittently rather than continuously.
Rodacki et al. (97) found that despite the
moderate values of compression associ-
ated with the traditional crunch, the
transient nature of the load (i.e., the short
peak period of compressive spinal force)
did not induce fluid loss. In fact,
abdominal flexion exercise was actually
found to be superior to the Fowler’s
position (a semi-recumbent position
used in therapy to alleviate pressure on
the spine) with respect to spinal unload-
ing, presumably mediated by a greater
fluid influx rate than when sustaining
a static recumbent posture (97).
It should also be noted that after
an exercise bout, spinal tissues are
allowed to recuperate until the next
training session, thereby alleviating
disc stress and affording the structures
time to remodel. Exercise-induced disc
damage results when fatigue failure
outpaces the rate of adaptive remodel-
ing, which depends on the intensity of
load, the abruptness of its increase, and
the age and health of the trainee (2).
Provided that dynamic spinal exercise
is performed in a manner that does not
exceed individual disc-loading capac-
ity, the evidence would seem to suggest
a positive adaptation of the supporting
tissues. In support of this contention,
Videman et al. (136) found that
moderate physical loading resulted in
the least disc pathology, with the
greatest degeneration seen at extreme
levels of activity and inactivity.
In addition, the role of genetics needs to
be taken into consideration. Despite the
commonly held belief that spinal de-
generation is most often caused by the
wear and tear from mechanical loading,
this seems to play only a minor role in
the process (17). Instead, it has been
shown that approximately 74% of the
variance is explained by hereditary
factors (15). Battie et al. (17) identified
specific gene forms associated with disc
degeneration that hasten degenerative
vertebral changes in the absence of
repetitive trauma. Hereditary factors,
such as size and shape of the spinal
structures, and biochemical constituents
that build or break down the disc can
highly influence disc pathology, as can
gene-environment interactions (17).
In a case-control study involving 45
monozygotic male twin pairs, Battie
et al. (16) found that subjects who spent
more than 5 times more hours driving
and handled more than 1.7 times more
Table
Summary of in vitro studies on spinal biomechanics reporting spinal compression forces applicable to the crunch
exercise
Study
Type of
Spine
Number of
Subjects
Amount of
Compression, N
Number of
Cycles
Number of
Herniations
Callaghan and McGill (30) Porcine cervical 26 260–1,472 86,400 15
Drake et al. (35) Porcine cervical 9 1,472 6,000 7
Tampier et al. (123) Porcine cervical 16 1,472 4,400–14,00 8
Drake and Callaghan (36) Porcine cervical 8 1,500 10,000 8
Marshall and McGill (70) Porcine cervical 10 1,500 6,000 4
VOLUME 33 | NUMBER 4 | AUGUST 201110
To Crunch or Not to Crunch
occupational lifting showed no in-
creases in disc degeneration compared
with their twin siblings and, although
values did not reach statistical signifi-
cance, actually displayed fewer lower
lumbar disc herniations. In addition,
Varlotta et al. (133) found that the
relative risk of lumbar disc herniation
before the age of 21 years is approxi-
mately 5 times greater in subjects who
have a positive family history. Further-
more, physically active individuals seem
to experience less back pain than
sedentary individuals (44,78).
Moreover, the studies in question do
not necessarily replicate spinal motion
during dynamic lumbar flexion exer-
cise. For example, the traditional
crunch exercise involves flexing the
trunk to approximately 30� of spinal
flexion so that only the head and
shoulders are lifted from the floor,
making the thoracic spine the region of
greatest flexion motion (105,117). Fur-
ther, Adams and Hutton (6) showed
that taking a flexed lumbar spine from
an end range of flexion at 13� to 11� of
flexion, a 2� differential, resulted in
a 50% reduction in resistance to
bending moment and therefore a 50%
reduction in bending stress to the
posterior annulus and intervertebral
ligaments. Thus, both the location
and degree of flexion will have a signif-
icant impact on spinal kinetics.
Finally, although abdominal exercises
create compressive forces by way of
muscular contraction, they also in-
crease intra-abdominal pressure (IAP)
(32). Three-dimensional biomechani-
cal models predict reductions in com-
pressive forces of approximately 18%
when IAP is factored into spinal flexion
efforts (118). Hence, IAP produced
during spinal flexion exercise may
serve to moderate compressive forces,
helping to unload the spine and
facilitate fluid absorption in the discs
(97). Because in vitro research models
to date have not incorporated IAP,
conclusions drawn may be limited with
respect to the safety of spinal flexion
exercises. However, it should be noted
that the unloading effects of IAP
may be diminished withhigh levels
of abdominal muscle coactivation (12).
Additional research is needed to shed
further light on this topic with partic-
ular attention focused on evaluating
the effects of IAP on compressive
forces in subjects performing spinal
flexion exercise including the crunch.
It should also be noted that some
epidemiological studies show an in-
creased risk of spinal injuries in athletes
involved in sporting activities that re-
quire repeated spinal flexion. Injuries to
the spinal column, including disc de-
generation and herniations, have been
found to occur with greater frequency in
gymnasts, rowers, and football players
(120,122,135,144). Furthermore, elite
athletes experience such injuries more
frequently than nonelite athletes
(88,120). However, a cause-effect re-
lationship between spinal flexion and
injury in these athletes has not been
established, and the ballistic nature of
such sporting activities has little appli-
cability to controlled dynamic abdom-
inal exercises.
BENEFITS OF SPINAL FLEXION
EXERCISES
If dynamic flexion exercises in fact do
not pose a significant injury risk in the
absence of spinal pathology, then the
natural question is whether performing
these movements confers benefits over
and above static-based exercises. The
following potential benefits can be
identified.
First, spinal motion has been shown to
facilitate nutrient delivery to the in-
tervertebral discs (50,51). The mecha-
nism of action is theorized to be related
to a pumping action that augments
transport and diffusion of molecules into
discs. Motion causes more fluid to flow
out of the disc, which is reversed when
the spine is unloaded (5). Fluid flow is
better at transporting large molecules,
whereas diffusion is better at trans-
porting smaller molecules (128). This
has a particular significance for spinal
tissue given that age-related decreases in
disc nutritional status is considered
a primary cause of disc degeneration,
leading to an accrual of cellular waste
products, degradation of matrix mole-
cules, and a fall in pH levels that further
compromise cell function and possibly
initiate apoptosis (27,52,71,130).
Postures involving flexion of the spine
are superior to neutral and extended
postures in terms of promoting in-
creased fluid exchange in the disc,
especially the nucleus pulposus (5).
One deficiency of neutral posture is
that it favors diffusion in the anterior
portion of the disc over the posterior
portion. Flexed postures reverse this
imbalance by stretching the posterior
annulus, thereby decreasing the dis-
tance for nutrients to travel. The
posterior region of the disc contains
a region that is deficient of nutrient
supplement from all sources (69), and
flexion reduces the thickness of the
posterior portion of the disc by 37%,
which ensures sufficient supply of
glucose to the entire posterior region
of the disc (5). Flexion increases
diffusion of small solutes and fluid flow
of large solutes. This is important
considering that disc degeneration has
been linked to inadequate metabolite
transport (51,83) and that populations
adopting flexed postures show less
incidence of disc disease (40). The
crunch exercise produces tensile
stresses on the posterior annulus—in
flexion, the posterior annulus has been
shown to extend up to 60% of its
original height (90)—and tensile stress
has shown to exert a protective effect on
disc cells by decreasing the expression
of catabolic mediators during inflam-
mation (107). By enhancing nutrient
uptake and limiting inflammatory-based
catabolism, regimented flexion exercise
may actually confer a positive effect on
the long-term spinal health and pro-
mote disc healing in the periphery (9).
In fact, research suggests that spinal
flexion and extension exercises can be
valuable in reducing LBP (38,43,96).
Although pain or lack of pain is not
necessarily an indicator of spinal health,
it nevertheless is interesting to speculate
that spinal flexion movements may
actually confer therapeutic benefits pro-
vided exercise does not exceed the
adaptive capacity of the tissue.
In addition, spinal flexion exercises
may help to improve functional spinal
Strength and Conditioning Journal | www.nsca-lift.org 11
flexibility and thereby reduce the onset
of LBP. Multiple studies have found that
a lack of sagittal plane spinal flexibility is
associated with an increased incidence
of LBP (28,37,73,89). Resistance exer-
cise has been shown to serve as an active
form of flexibility training, helping to
improve joint mobility within a func-
tional range of motion (14,80,106), and
spinal flexion exercises have been
shown to increase sagittal plane spinal
mobility (38). Improved flexibility asso-
ciated with resistance training has been
attributed to increased connective tissue
strength, increased muscular strength,
and improved motor learning, and/or
neuromuscular coordination (80). At
the same time, dynamic strengthening
of the supporting musculature and
ligamentous tissue may attenuate spinal
hypermobility in those afflicted, which
has also been implicated as a cause of
LBP (119). Hence, a case can be made
that a well-designed resistance training
program that includes dynamic spinal
flexion may bestow a preventative effect
against LBP. However, it should be
noted that some studies have failed to
reveal significant differences in the
sagittal plane spinal flexibility between
pain free subjects and those with LBP
(94), and 1 study indicated that lumbar
spinal flexibility is associated with disc
degeneration (48). Moreover, we cannot
necessarily determine a cause-effect re-
lationship between poor spinal flexibility
and an increased risk of injury. Further
research is warranted to draw pertinent
conclusions on the topic.
Finally, flexion-based spinal movements
help to optimize hypertrophy of the
rectus abdominis muscle. The crunch
exercise and its variations have been
shown to target the rectus abdominis to
a much greater extent than the other
core muscles. McGill (74) found that
a variant of the crunch activated 50%
of maximal voluntary contraction
(MVC) of the rectus abdominis but only
20%, 10%, 10%, and 10% of MVC of the
external obliques, internal obliques, trans-
verse abdominis, and psoas major,
respectively. Given that a direct associ-
ation has been noted between muscle
cross-sectional area and muscle strength
(42,72), muscle hypertrophy has specific
relevance to athletes who require exten-
sive core strength. Moreover, muscle
hypertrophy of the rectus abdominis is
also integral to aesthetic appearance of
the abdominal musculature and is there-
fore highly desired by bodybuilders and
other fitness enthusiasts.
The hypertrophic superiority of dy-
namic movement can be partly attrib-
uted to the eccentric component,
which has been shown to have the
greatest effect on promoting muscle
development (41,49,53,100). Eccentric
exercise has been linked to a preferen-
tial recruitment of fast twitch muscle
fibers (85,112,121) and perhaps re-
cruitment of previously inactive motor
units (77,84). Given that fast twitch
fibers have the greatest growth poten-
tial, their recruitment would necessar-
ily contribute to greater increases in
muscle cross-sectional area.
Eccentric exercise is also associated
with greater muscle damage, which
has been shown to mediate a hypertro-
phic response (77,108). Muscle damage
induced by eccentric exercise upregu-
lates MyoD messenger RNA expression
(57) and has been implicated in the
release of various growth factors that
regulate satellite cell proliferation and
differentiation (126,137).
In addition, dynamic muscle actions
have been shown to induce significantly
greater metabolic stress than static
contractions (25). Specifically, the
buildup of metabolites, such as lactate,
hydrogen ion, and inorganic phosphate,
has been shown to mediate a hypertro-
phic response (101,109,116), and some
researchers have speculated that meta-
bolic stress may be more important
than high force development in opti-
mizing muscle development (113). The
stress-inducedmechanisms theorized to
increase muscle hypertrophy include
alterations in hormonal milieu, cell
swelling, free radical production, and
increased activity of growth-oriented
transcription factors (108). Russ (104)
displayed that phosphorylation of Akt,
a protein kinase associated with mTOR
pathway signaling and thus regulation
of protein synthesis, is significantly gre-
ater in eccentric contractions compared
with isometric contractions. This may
be because of heightened metabolic
stress, greater muscle damage, or a com-
bination of both.
PRACTICAL APPLICATIONS
Taking all factors into account, it would
seem that dynamic spinal flexion ex-
ercises provide a favorable risk to
reward ratio provided that trainees
have no existing spinal injuries or
associated contraindications, such as
disc herniation, disc prolapse, and/or
flexion intolerance. However, several
caveats need to be taken into consid-
eration to maximize spinal health.
First and foremost, because hereditary
factors have a tremendous impact on
the disc degeneration, it is difficult to
know the precise amount of volume,
intensity, and frequency sufficient to
stimulate soft tissue strengthening adap-
tations without exceeding the recovery
ability of the spine. It has been theorized
that a ‘‘safe window’’ of tissue mechan-
ical loading exists that facilitates healthy
maintenance of spinal discs (119). There
is evidence supporting this theory
because it pertains to spinal compres-
sion (145); however, further research is
needed to determine whether this
applies to other types of spinal loading
including flexion.
An epidemiological study by Mundt
et al. (82) found that participation in
sports such as baseball, softball, golf,
swimming, diving, jogging, aerobics,
racquet sports, and weight lifting are
not associated with increased risk of
lumbar disc herniation, and they even
may offer a protective effect against
herniation. Kelsey et al. (58) reported
similar findings with respect to disc
prolapse. Many of these sports involve
a high frequency of spinal motion
including flexion, which casts doubt
on the theory that humans have
a limited number of flexion cycles.
Unfortunately, there is no way to
determine when an individual’s train-
ing volume and/or intensity falls out-
side this range and thus predisposes the
spine to localized overload injury.
VOLUME 33 | NUMBER 4 | AUGUST 201112
To Crunch or Not to Crunch
Given that the spine and core muscu-
lature are loaded during nonmachine-
based exercise performance, such as
during squats, deadlifts, chin-ups, and
push-ups, most training can be consid-
ered ‘‘core training.’’ Therefore, it is
best to err on the side of caution and
limit the amount of lumbar flexion
exercise to ensure that the tissue
remains in ‘‘eustress’’ and does not
become ‘‘distressed.’’ Based on the
current data, the authors recommend
that a sound core strengthening rou-
tine should not exceed approximately
60 repetitions of lumbar flexion cycles
per training session. Untrained individ-
uals should begin with a substantially
lower volume. A conservative estimate
would be to start with 2 sets of 15
repetitions and gradually build up
tolerance over time.
In addition, it is important to allow for
sufficient rest between dynamic spinal
flexion sessions. The time course of
postexercise muscle protein synthesis
lasts approximately 48 hours (67). Train-
ing a muscle group before protein
synthesis has completed its course can
impair muscle development (47) and
potentially lead to localized overtraining.
Thus, the notion that it is optimal to
perform dynamic abdominal exercises
on a daily basis is misguided. Because the
intervertebral discs are poorly vascular-
ized with low levels of metabolite trans-
port, their rate of remodeling lags behind
that of other skeletal tissues (69,115),
which may necessitate even greater time
for recuperation. Taking all factors into
account, a minimum of 48 hours should
be afforded between dynamic spinal
flexion exercise sessions, and it may be
prudent to allow 72 hours or more
depending on individual response.
Although some core training programs
include ultrahigh repetition sets of
crunches, for example, multiple sets
of a hundred repetitions or more, this
type of protocol has little functional
applicability. After all, when does an
individual need to continuously flex the
spine in everyday life? It is therefore
recommended that flexion-based spi-
nal exercises be reserved for impro-
ving strength and/or hypertrophy of
the abdominal musculature as opposed
to heightening muscular endurance. A
repetition range of approximately 6–15
repetitions is advised for achieving this
goal (108). External resistance should
be used when necessary to elicit an
overload response within this target
repetition range. Those seeking im-
provements in local muscular endur-
ance would be best served by
performing static, neutral posture ex-
ercises that are held for extended
periods. Specific guidelines will vary
dramatically according to the individ-
ual’s needs and abilities, but a general
recommendation for untrained individ-
uals would be to perform 3–4 sets of
10- to 15-second holds in multiple
planes. Advanced exercisers seeking
increases in static endurance might
perform 3–4 sets of 60 seconds or more
in multiple planes, whereas advanced
exercisers seeking increases in static
power could stick to the 10- to 15-
second holds but perform more chal-
lenging variations or increase external
resistance to promote further adapta-
tion. Athletes who engage in sports
where spinal flexion exercise or other
inherently dangerous motions for the
discs, such as spinal rotation, is prom-
inent and volumes of flexion cycles and
training frequencies above our recom-
mendations are exceeded should con-
sider the possibility of excluding spinal
flexion exercise from their routines.
Exercise tempo is another important
consideration. Several studies have
shown that repetitions performed at
a speed of 1 second elicit greater
muscle activation than those per-
formed more slowly (134), and faster
repetitions may selectively recruit the
rectus abdominis (87). Given the
principle of specificity, rapid speeds
of movement would also tend to have
greater transfer to athletic activities
that require dynamic core power, such
as wrestling (54), throwing a baseball
(56), tennis (33), gymnastics (91),
soccer (125), swimming (68), and track
and field (46). However, an increased
repetition speed could subject the spinal
tissues to excessive forces that may
lead to injury (6,86). For nonathletic
populations, the risks of faster repeti-
tions would appear to outweigh the
potential rewards and thus a slightly
slower tempo of approximately 2 sec-
onds may be more appropriate with
respect to maintaining spinal health. As
for athletic populations, more research
is needed to show whether explosive
dynamic core exercises lead to positive
adaptations that strengthen tissues and
prevent injury or whether they subject
the athlete to greater risk of injury by
adding more stress to the tissues.
It also is important to consider the
effects of diurnal variation on spinal
kinetics. During sleep, loading on the
discs is reduced, allowing them to
absorb more fluid and increase in
volume (129). Fluid is then expelled
throughout the day as normal daily
spinal loading ensues. In the early
morning, intradiscal pressure is 240%
higher than before going to bed (140),
and bending stresses are increased at
the discs by 300% and at the ligaments
of the neural arch by 80% because of
hydration and absence of creep (4). As
the day goes on, discs bulge more,
become stiffer in compression, become
more elastic and flexible in bending,
affinity for water increases, and the risk
of disc prolapse decreases (1). After just
30 minutes of waking, discs lose 54% of
the loss of daily disc height and water
content and 90% within the first hour
(95). For this reason, spinal flexion
exercises should be avoided within at
least 1 hour of rising. To be conserva-
tive, athletes may wantto allow
a minimum of 2 hours or more before
engaging in exercises that involve
spinal flexion.
There is some evidence that spinal
flexion exercises should also be
avoided after prolonged sitting. It has
been shown that discs actually gain
height after sitting (11,61) and decrease
lumbar range of motion (31), which
reduces slack in the flexion-resisting
structures including ligaments and the
posterior annulus while increasing the
risk of injury to those structures (4,18).
However, as noted by Beach et al. (18),
individual differences in sitting pos-
ture lead to large variations in tissue
Strength and Conditioning Journal | www.nsca-lift.org 13
response. Some individuals actually
gain lumbar range of motion from
sitting, which can also increase the risk
of injury because of viscoelastic creep
(76), stress relaxation (3), or fluid loss
(5), which increases joint laxity (4).
Considering that approximately 50% of
stiffness is regained within 2 minutes of
rising after 20 minutes of full flexion
(76), it seems prudent to allow at least
several minutes to elapse, perhaps 5 or
more, before engaging in spinal flexion
exercises after a period of prolonged
sitting and to walk around to facilitate
dehydration of the disc.
CONCLUSION
Based on current research, it is premature
to conclude that the human spine has
a limited number of bending cycles. The
claim that dynamic flexion exercises
are injurious to the spine in otherwise
healthy individuals remains highly spec-
ulative and is based largely on the
extrapolation of in vitro animal data that
is of questionable relevance to in vivo
human spinal biomechanics. Although it
appears that a large number of contin-
uous bending cycles may ultimately have
a detrimental effect on spinal tissues,
no evidence exists that a low-volume
strength-based exercise routine that
includes dynamic spinal flexion move-
ments will hasten the onset of disc
degeneration, and a case can be made
that such exercises may in fact produce
a beneficial effect in terms of disc health.
Contraindications for spinal flexion
movements would only seem applicable
with respect to those with existing spinal
pathology, such as disc herniation/
prolapse or flexion intolerance.
To date, the authors are not aware of
any study that has investigated the
effects of spinal flexion exercise on
human spines in vivo. Further research
is needed to evaluate both the acute
and chronic effects of dynamic spinal
flexion exercises in human subjects
in vivo so that more definitive con-
clusions can be drawn on the topic.
This research should include magnetic
resonance imaging of intervertebral
discs to assess disc health preceding
and following human spinal flexion
protocols of varying loads, repetitions,
tempos, and ranges of motion. It is
hoped that this article will serve to
spark new research in this area.
With respect to program design, basic
core strength and endurance will be
realized through performance of most
nonmachine-based exercises such as
squats, rows, deadlifts, and push-ups.
That said, targeted core exercises may
serve to enhance sports performance,
functional capacity, and physique aes-
thetics. Consistent with the principle of
specificity, core program design should
take into account the individual goals
and abilities of the exerciser with respect
to their need for muscular hypertrophy,
power, strength, and/or endurance, and
the types of joint actions involved in
their sport. A variety of abdominal
exercises are necessary to sufficiently
work the abdominal musculature, and
these exercises will differ based on
training objectives (13). Variety in spinal
loading is associated with lower risk of
spinal pathology (136). A balanced
multiplanar approach to core training
that incorporates a combination of
isometric and dynamic exercises is
warranted to prevent any particular
spinal segment from accentuated stress
and to ensure proper spine-stabilizing
biomechanics.
Bret Contreras
is currently pursu-
ing his PhD at
AUT University.
Brad
Schoenfeld is
the owner/director
of Global Fitness
Services.
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Cs-Szabo G. Age related changes in the
extracellularABSTRACT
The objective of this study was to evaluate and classify indirectly the level of core muscle strength 
in beginners in a academy based on Kendall’s assessment test. The sample consisted of 1317 (536 
male and 781 female) beginners in a fitness facility of Sâo Paulo, submitted to Kendall’s assessment 
test, grouped by age (20 to 29 years, 30 to 39, 40-49 years, and 50-59 years) and gender. Analysis of 
percentage were performed , and compared to the total percentage of the scores obtained in the test. 
It was concluded that the vast majority of people did not present an adequate degree of strength and 
core stability based on the Kendall’s evaluation.
Keywords: biomechanics, training, performance.
Autor de correspondência: 
Paulo H. Marchetti
Universidade Metodista de Piracicaba 
Rodovia do Açúcar Km 156, Bloco 7, Sala 39, Taquaral 
13423-070 - Piracicaba, SP – Brasil 
E-mail: pmarchetti@unimep.br
1Grupo de Pesquisa em Performance Humana, Programa de Pós-
Graduação Stricto Sensu em Ciências do Movimento Humano, Faculdade 
de Ciências da Saúde (FACIS), UNIMEP, Piracicaba, SP, Brasil; 
2Faculdades de Educação Física da FMU, São Paulo, Brasil; 
3Instituto de Ortopedia e Traumatologia, Faculdade de Medicina, Universidade de São Paulo, 
São Paulo, Brasil.
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 2
1. INTRODUÇÃO
Uma prescrição de treinamento adequada 
é uma das responsabilidades primordiais de 
instrutores e treinadores em academias, e está 
relacionada à escolha dos exercícios e variáveis 
de carga, considerando principalmente o nível 
atual de condicionamento físico do cliente 
(MARCHETTI e LOPES, 2014)1. Dentre as 
diversas atividades de academia, a chamada 
musculatura do core acaba sendo empregada 
na maioria das vezes como objetivo de 
estabilização, equilíbrio e transferência de 
forças entre segmentos (aumento da rigidez 
estrutural). De acordo com Behm et al. 
(BEHM, DRINKWATER, WILLARDSON e 
COWLEY, 2010)2 o conceito anatômico de core 
baseia-se no esqueleto axial (cintura pélvica 
e escapular), os tecidos moles (articulações, 
fibro-cartilagem, ligamentos, tendões, fáscias e 
músculos) se originando no próprio esqueleto 
axial (os quais podem possuir inserções axiais 
ou apendiculares como os segmentos).
 Estudos indicam que a força e 
potência podem ser afetadas por uma limitada 
capacidade de rigidez/estabilidade do core, 
influenciando a transferência de forças entre 
segmentos. A estabilidade/rigidez do core pode 
ser representada pela interação de 3 subsistemas 
(neural, passivo e ativo), os quais deveriam ser 
considerados principalmente em programas 
de treinamento onde os níveis de força do 
mesmo são baixos (BEHM, DRINKWATER, 
WILLARDSON e COWLEY, 20103; BEHM 
e SANCHEZ, 20124; 20134). Desta forma, 
clientes que apresentam baixo nível de força do 
core podem apresentar dificuldades em outras 
atividades de academia como musculação, 
natação, ginástica, treinamento funcional entre 
outras. Portanto, uma prévia avaliação do core 
pode ser considerada uma ferramenta útil para 
a implementação de exercícios específicos e/
ou complementares ao programa regular na 
academia. 
O objetivo deste estudo foi avaliar 
e classificar o nível de força de forma 
indireta os músculos do core em indivíduos 
ingressantes de academia baseados na proposta 
de avaliação de Kendall et al., (1993)5. 
 
2. MATERIAIS E MÉTODOS 
2.1.Participantes
 A amostra foi composta por 1317 alunos 
ingressantes de uma academia de ginástica de 
São Paulo, submetidos a uma bateria de testes de 
avaliação física, sendo 536 do sexo masculino 
e 781 do sexo feminino, agrupados por faixas 
etárias entre 20 a 29 anos, 30 a 39 anos, 40 a 
49 anos e 50 a 59 anos. Os critérios de inclusão 
adotados foram os seguintes: 1) sem quaisquer 
cirurgias, lesões ou qualquer acometimento 
músculo-esquelético em membros inferiores 
(menos de 1 ano); 2) não terem treinado os 
membros inferiores nas 48 horas antecedentes 
ao protocolo experimental; 3) não apresentarem 
desordens neurológicas periféricas e/ou 
centrais; 4) serem capazes de realizar os testes 
propostos. Todos os sujeitos foram informados 
dos procedimentos experimentais e assinaram
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 3
o termo de consentimento livre e esclarecido, 
aprovado pelo Comitê de Ética em Pesquisa da 
Universidade. 
2.2.Procedimentos
 Os sujeitos se apresentaram apenas 
uma vez ao laboratório onde foi realizado um 
teste de abaixamento dos membros inferiores 
baseado no teste de Kendall (KENDALL, MC-
CREARY e PROVANCE, 1993)5, partindo da 
posição inicial em decúbito dorsal, membros 
inferiores na vertical estabelecendo um ângulo 
de 90° com o solo; com o objetivo de graduar 
a força dos músculos abdominais e flexores de 
quadril (Figura 1). O sujeito recebeu instruções 
do avaliador, como segue: Posição inicial em 
decúbito dorsal, antebraços flexionados sobre 
o tórax, elevação de um membro inferior por 
vez, até a posição vertical e manutenção dos 
joelhos estendidos. Inclinação posterior da 
pelve, retificando a coluna lombar sobre o solo 
e manutenção desta posição durante o teste. 
Cabeça e ombros devem permanecer encosta-
dos no solo. A execução do teste consistiu em 
o indivíduo abaixar lenta e simultaneamente os 
membros inferiores, mantendo a pelve em in-
clinação posterior.
FIGURA 1. Teste de abaixamento de membros inferiores: (a) início da avaliação; (b) máxima amplitude atingida 
(KENDALL, MCCREARY e PROVANCE, 1993).
A força foi graduada baseando-se na 
capacidade de manter a região lombar 
retificada sobre a superfície durante o 
abaixamento lento de ambos os membros 
inferiores. A força de contração excêntrica 
exercida pelos músculos flexores do quadril 
e pelo abaixamento dos membros inferiores 
tende a inclinar a pelve anteriormente, atuando 
como uma forte resistência contra os músculos 
abdominais, que estão tentando manter a 
pelve em inclinação posterior. No momento 
em que a pelve se inclina anteriormente e a 
região lombar se arqueia ,caracteriza-se a 
instabilidade, e o teste é interrompido. 
Avaliação indireta da força dos músculos do core em iniciantes de academia
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A força dos músculos abdominais é graduada 
através do ângulo formado entre os membros 
inferiores estendidos e o solo. Para a determi-
nação do ângulo em graus, foi utilizado um 
flexímetro (Sanny, Sanny do Brasil) posiciona-
do no tornozelo esquerdo do avaliado. O teste 
foi sempre realizado na mesma hora do dia e 
pelo mesmo avaliador. 
2.3. Análise dos Dados
 A escala para a graduação da força 
muscular utilizada e o código para tal gradu-
ação seguem a referência de Kendall (KEND-
ALL, MCCREARY e PROVANCE, 1993)5, a 
qual retrata cada possível ângulo em grau e seu 
correspondente índice qualitativo (Figura 2) e a 
tabela 1 mostra o código para a graduação mus-
cular.
Figura 2. Escala de graduação ângulo/ìndice.
Função do músculo Graus musculares e símbolos
Mantém a posição do teste (sem acrescentar pressão). Regular 5
Mantém a posição do teste contra uma pressão discreta. Regular + 6
Mantém a posição de teste contra uma pressão discreta a moderada. Bom - 7
Mantém a posição de teste contra uma pressão moderada. Bom 8
Mantém a posição de teste contra uma pressão moderada a forte. Bom + 9
Mantém a posição de teste contra uma pressão forte Normal 10
Tabela 1. Código para a graduação muscular.
Avaliação indireta da força dos músculos do core em iniciantes de academia
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VOLUME 33 | NUMBER 4 | AUGUST 201118
To Crunch or Not to Crunch
	Core Strengthening
	ANATOMY
	General Overview
	Osseous and Ligamentous Structures
	Thoracolumbar Fascia
	Paraspinals
	Quadratus Lumborum
	Abdominals
	Hip Girdle Musculature
	Diaphragm and Pelvic Floor
	Exercise of the Core Musculature
	Decreasing Spinal and Pelvic Viscosity
	Grooving Motor Patterns
	Stabilization Exercises
	Functional Progression
	Core Strengthening for Sports: Moving Past Remedial Core Training
	Efficacy of Core-Strengthening Exercise
	Core Strengthening to Prevent Injury and Improve Performance
	Core Strengthening for Treatment of Back Pain
	CONCLUSIONS
	References1 | Ano 2015 | p. 5
2.4. Análise Estatística
 Foram realizadas análises de percentu-
al, onde o grupo total de sujeitos foi separado 
em diferentes amostras como gênero e idade, e 
comparados em relação ao percentual total dos 
escores obtidos no teste. 
3. RESULTADOS
 Considerando o grupo total de sujeitos 
da amostra (n=1317), observou-se que apenas 
2,15% apresentaram classificações entre “Bom 
+” e “Normal”, 
sendo que 68,8% ficaram entre as classificações 
“Regular +” e “Bom -” (Tabela 2). 
Tabela 2 - Classificação geral do nível de força 
do core
Graduação n %
Regular - 269 15,8
Regular + 611 35,9
Bom - 525 30,9
Bom 265 15,6
Bom + 20 1,2
Normal 11 0,6
 Separando a amostra quanto ao gênero 
observou-se que os homens (n=536) apresenta-
ram 2,4% e as mulheres (n=781) apenas 1,8% 
nas classificações “Bom +” e “Normal”, sendo 
que a maior parte deles encontrou-se nas cate-
gorias “Regular +” e “Bom-” (homens= 64,4% 
e mulheres=68,8%) (Tabela 3).
Tabela 3- Classificação por gênero do nível de 
força do core.
Graduação Homens Mulheres
n % n %
Regular - 73 10,3 196 19,8
Regular + 220 31,0 391 39,5
Bom - 237 33,4 288 29,1
Bom 163 23,0 102 10,3
Bom + 10 1,4 10 1,0
Normal 7 1,0 4 0,4
 Separando a amostra de forma geral, 
quanto a faixa etária, observou-se que dos 1317 
indivíduos, uma pequena porcentagem encon-
trou-se entre “Bom +” e “Normal”, sendo que 
a maioria se concentraram entre “Regular +” e 
“Bom -” (Tabela 4).
Graduação
20-29 anos 30-39 anos 40-49 anos 50-59 anos
n % n % n % n %
Regular - 59 13,5 49 11,3 33 10,7 20 14,8
Regular + 160 36,6 172 39,5 98 31,9 43 31,9
Bom - 137 31,4 135 31,0 121 39,4 40 29,6
Bom 74 16,9 74 17,0 48 15,6 27 20,0
Bom + 5 1,1 5 1,1 5 1,6 3 2,2
Normal 2 0,5 3 0,7 2 0,7 2 1,5
Tabela 4. Classificação geral por faixa etária do nível de força do core
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 6
Separando a amostra quanto a faixa etária e 
gênero, observou-se que os homens (n=536), 
apresentaram uma baixa porcentagem entre 
“Bom +” e “Normal”, porém, para as idades 
entre 40 e 49 anos, assim como para as idades 
entre 50 e 59 anos, não foram observados in-
divíduos na classificação “Normal”. Para todas 
as faixas etárias, aproximadamente 25% dos 
indivíduos homens encontraram-se na classifi-
cação “Bom” (Tabela 5).
Graduação
20-29 anos 30-39 anos 40-49 anos 50-59 anos
n % n % n % n %
Regular - 10 5,0 9 5,5 6 5,3 5 8,6
Regular + 65 32,5 51 31,1 31 27,2 20 34,5
Bom - 70 35 55 33,5 49 43 16 27,6
Bom 50 25 43 26,2 27 23,7 16 27,6
Bom + 3 1,5 3 1,8 1 0,9 1 1,7
Normal 2 1,0 3 1,8 0 0,0 0 0,0
Separando a amostra de mulheres (n=781), 
quanto a faixa etária, apresentaram uma 
pequena porcentagem entre “Bom +” e 
“Normal”, para as idades entre 20 e 29 anos, 
assim como para as idades entre 30 e 39 anos, 
entretanto, não foram observados indivíduos 
na classificação “Normal” (Tabela 6).
Tabela 5. Classificação dos homens por faixa etária do nível de força do core
Graduação
20-29 anos 30-39 anos 40-49 anos 50-59 anos
n % n % n % n %
Regular - 49 20,7 40 14,6 27 14,0 15 19,5
Regular + 95 40,1 121 44,2 67 34,7 23 29,9
Bom - 67 28,3 80 29,2 72 37,3 24 31,2
Bom 24 10,1 31 11,3 21 10,9 11 14,3
Bom + 2 0,8 2 0,7 4 2,1 2 2,6
Normal 0 0,0 0 0,0 2 1,0 2 2,6
Tabela 6. Classificação das mulheres por faixa etária do nível de força do core
4. DISCUSSÃO
Conhecimentos cinesiológicos e biomecânicos 
sobre o core tem se consolidado cada vez tanto 
em relação ao treinamento e à reabilitação. As 
dores lombares têm sido relacionadas com o 
atraso na ativação do transverso do abdome, 
atrofia dos multifidos, fraqueza dos músculos 
extensores, déficit na propriocepção espinhal, 
equilíbrio e resposta à perturbações (BARR ET 
AL., 20076; GARRY ET AL., 20087; HIDES 
ET AL., 19968; HODGES & RICHARDSON, 
19969; KIBLER, 200610). Assim, a estabilidade 
do core como prevenção de lesões na região 
lombar e em outras regiões do corpo e o 
treinamento desta musculatura têm sido 
recomendados como promoção de um regime 
preventivo e terapêutico (AKUTHOTA & 
NADLER, 200411; WILLSON ET AL., 200512). 
Vilela Junior, Hauser, et al (201113) ressaltam 
que a estabilidade anterior da coluna vertebral
Avaliação indireta da força dos músculos do core em iniciantes de academia
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é realizada pelos músculos reto do abdome, oblíquos 
interno e externo, cujas forças resultantes, em con-
dições ideais, devem formar entre si ângulos retos 
com ortogonalidade espacial; ao passo que a esta-
bilidade posterior da coluna vertebral é realizada 
pelos músculos eretores da espinha, interespinhais, 
intertransversais, quadrado lombar e serrátil poste-
rior. Então, cabe ao professor/ treinador prescrever 
exercícios para o fortalecimento destes complexos 
musculares.
 Reinehr et al. (200814) estudaram como um 
programa de exercícios para a estabilização do core 
influencia a estabilidade e a ocorrência de dor lom-
bar, e verificaram que após o treinamento houve 
diminuição da dor lombar e aumento da força ab-
dominal e estabilidade do core. Este artigo corrob-
orou os resultados do presente estudo, pois foi apli-
cado o mesmo teste de abaixamento dos membros 
inferiores. Verificaram que os indivíduos portadores 
de dores lombares crônicas, no pré-treinamento es-
tavam situados na classificação para o nível de força 
do core nos graus 0,1 e 2; o que correspondeu neste 
estudo aos graus 5, 6 e 7 que significam respectiva-
mente a Regular, Regular + e Bom -. No pós-trein-
amento estes indivíduos obtiveram ganho de força 
e estabilidade do core, alcançando graus 4 e 5, cor-
respondentes neste estudo aos graus 9 e 10, que sig-
nificam respectivamente a Bom + e Normal. Os au-
tores concluíram que os ganhos de força abdominal 
indicaram que este tipo de programa de treinamento 
para o core foi efetivo para o aumento da força e 
estabilidade core e diminuição da lombalgia. 
Neste presente estudo, os indivíduos ingressantes na 
academia de ginástica que foram avaliados no teste 
de abaixamento dos membros inferiores, em sua 
maioria, foram classificados para o nível de força 
do core nos graus 5, 6 e 7 significando, respectiva-
mente, Regular, Regular + e Bom -. 
 De acordo com o código para a graduação 
muscular, as funções dos músculos para as classi-
ficações acima, representam um estado de pouca 
força e estabilidade do core, já que os mesmos não 
suportaram a posição do teste contra pressões acima 
de moderadas. Para a classificação 8 (Bom), onde 
se mantem a posição do teste contra uma pressão 
moderada, apenas 16,9% dos indivíduos avali-
ados conseguiram este grau. Quando separados por 
gênero, os homens atingiram 25,4% e as mulheres 
apenas 11,1%. No código para graduação muscular, 
os graus 9 e 10 (Bom + e Normal), significam que o 
indivíduo consegue manter a posição do teste contra 
pressões moderada a forte e forte respectivamente. 
Dos avaliados neste estudo, apenas 2,1% obtiveram 
as classificações Bom + e Normal. Quando a 
classificação foi separada por faixa etária e gênero, 
observou-se que, para todas as idades, a grande 
porcentagem dos indivíduos ficou entre as classifi-
cações Regular-, Regular + e Bom -. Os homens de 
40 a 49 anos e 50 a 59 anos, não conseguiram a 
classificação Normal, sendo que as mulheres que 
não atingiram essa classificação foram as de 20 a 29 
anos e 30 a 39 anos. 
 A partir dos resultados encontrados neste 
estudo, observa-se que a grande maioria dos indi-
víduos não apresentou um grau adequado de força e 
estabilidade do core.
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 8
Tal fato, muito provavelmente,é consequên-
cia do enfraquecimento dos músculos que es-
tabilizam anterior e posteriormente a coluna 
vertebral e do desequilíbrio entre as forças 
resultantes exercidas sobre a pélvis que sofre 
um torque resultante no sentido anterior, espe-
cialmente fruto do enfraquecimento do reto do 
abdome e consequente inclinação anterior da 
coluna lombar acentuando a lordose da mesma 
(VILELA JUNIOR, HAUSER, 201113). Neste 
sentido, fica patente que um core em condições 
biomecânicas ideais, depende do fortaleci-
mento harmônico dos eretores da espinha, dos 
extensores do quadril, dos flexores do quadril 
e dos abdominais, uma vez que o enfraqueci-
mento de um destes complexos musculares 
acarretará a rotação da pélvis e consequente-
mente a inclinação posterior ou anterior da 
coluna. O instrumento utilizado neste estudo, 
apesar de simples, avalia em última instância, 
o quanto o sujeito consegue estabilizar a pélvis.
 Akuthota et al., (200411) sugeriram que 
pessoas sedentárias, com enfraquecimento da 
musculatura estabilizadora, deveriam inicial-
mente ser submetidas a um programa de exercí-
cios para o fortalecimento do core, ao invés de 
realizarem os tradicionais exercícios abdomi-
nais (seat-ups), já que a realização destes, sem 
o devido fortalecimento do core, implica em 
lesões ou dores lombares. Juker et al. (198815) 
afirmaram que os seat-ups não são seguros 
devido a acentuada carga de compressão dos 
discos vertebrais. 
 Como as academias de ginástica pos-
suem diversos programas de exercícios e a aval-
iação física fornece subsídios para prescrevê-
los, seria interessante que fossem detectadas 
as reais condições de força e estabilidade do 
core dos alunos ingressantes para que as pre-
scrições fossem adequadas às necessidades dos 
mesmos. Entretanto, Pavin e Gonçalves (2010) 
abordaram a discussão sobre as controvérsias 
no uso de programas de exercícios para o core 
e as lombalgias (BERGMARK,1989; FARIES, 
& GREENWOOD, 200718; PANJABI, 199219; 
WILLARDSON, 200720). 
 Considera-se como uma das princi-
pais limitações do presente estudo a utilização 
do teste de um teste básico e genérico para a 
avaliação do core, sendo que o mesmo não 
abrange toda as estruturas necessárias para a 
avaliação. Entretanto, pode ser um teste adi-
cional ao programa de avaliação física de aca-
demia como teste adicional para auxiliar os 
instrutores quanto à potencial fragilidade do 
cliente. 
5. CONCLUSÃO
Conclui-se que a grande maioria dos indivídu-
os não apresenta um grau adequado de força e 
estabilidade do core baseados na proposta de 
avaliação de Kendall. 
 
6. REFERÊNCIAS
Avaliação indireta da força dos músculos do core em iniciantes de academia
Revista CPAQV – Centro de Pesquisas Avançadas em Qualidade de Vida | Vol. 7 | Nº. 1 | Ano 2015 | p. 9
1. Marchetti, P. H.& Lopes, C. R. (2014) Plane-
jamento e Prescrição do Treinamento Personali-
zado: do iniciante ao avançado. São Paulo: Mundo. 
2.Behm, D. G., Drinkwater, E. J., Willardson, J. 
M.& Cowley, P. M. (2010) The use of instability 
to train the core musculature. Applied Physiology, 
Nutrition and Metabolism, v. 35, p. 91-108. 
3. Behm, D. G. & Sanchez, J. C. C. (2013) Instabil-
ity Resistance Training Across the Exercise Contin-
uum. Sports Health: A Multidisciplinary Approach, 
p. 1-5.
4. Behm, D. G.& Sanchez, J. C. C. (2012) The ef-
fectiveness of resistance training using unstable 
surfaces and devices for rehabilitation. The Inter-
national Journal of Sports Physical Therapy, v. 7, n. 
2, p. 226-241.
5. Kendall, F. P., McCreary, E. K. & Provance, P. G. 
(1993) Muscles: Testing and Function. 4. Philadel-
phia: Williams and Wilkens. 
6. Barr, K.P., Griggs, M. & Cadby, P. (2007). Lum-
bar stabilization: a review of core concepts and cur-
rent literature, part 2. American Journal of Physical 
Medicine and Rehabilitation, 86 (6), 72-80.
7. Garry, T. A., Sue, L. M. & Brendan, L. (2008). 
Feedforward responses of tranverses abdominis 
are directionally specific and act asymmetrically: 
implications for core stability theories. Journal of 
Orthopardic and Sports Physical Theraphy, 38 (5), 
228-37. 
8. Hides, J. A., Richardson, C. A. & Jull, J. A. 
(1996). Multifidus muscle recovery is not automat-
ic after resolution of acute, first-episode low back 
pain. Spine, 21, 2763-9.
9. Hodges, P. W. & Richardson, C. A. (1996). In-
efficient muscular stabilization of the lumbar spine 
associated with low back pain: A motor control 
evaluation of transversus abdominis. Spine, 21, 
2640-2650.
10. Kibler, W. B., Press, J. & Sciascia, A. (2006). 
The hole of core stability in athletic function. Sports 
Medicine, 36 (3), 189-98.
11. Akuthota, V. & Nadler, S.F. (2004). Core 
strengthening. Archives of Physical Medicine and 
Rehabilitation.,85(3 Suppl 1),86-92.
12. Willson, J. D., Dougherty, C. P., Ireland, M. 
L. & Davis, I. M. (2005). Core stability and its re-
lationship to lower extremity function and injury. 
Journal of American Academy of Orthopaedic Sur-
gery, 13 (5), 316-25.
13. Vilela Junior, G. B. Hauser, M.W. et al (2011). 
Cinesiologia. Ponta Grossa, PR: Editora UEPG, 71- 
75.
14. Reinehr. F.B, Carpes F.P, Bolli M.C. (2008) 
Influência do treinamento de estabilização central 
sobre a dor e estabilidade lombar. Fisioterapia em 
movimento, 1,123-129.
15. Juker, D., McGill, S., Kropf, P. & Steffen, T. 
(1998). Quantitative intramuscular myoelectric ac-
tivity of lumbar portions of psoas and the abdomi-
nal wall during a wide variety of tasks. Medicine 
Science and Sports Exercise, 30, 301-310. 
16. Pavin, L. N. & Gonçalves, C. (2010). Principles 
of core stability in the training and in the rehabili-
tation: review of literature. Journal of Health and 
Scince Institute, 28 (1), 56-8.
17. Bergmark, A. (1989). Stability of the lumbar 
spine. A study in mechanical engineering. Acta Or-
thopaedica Scandinavica, 230, 1-54.
18. Faries, M. D. & Greenwood, M. (2007). Core 
training: stabilizing the confusion. Strength and 
Conditioning Journal, 29 (2), 10-25.
19. Panjabi, M. M. (1992). The stabilizing system 
of the spine. Part II. Neutral zone and instability hy-
pothesis. Journal of Spinal Disorders, 5, 390-397. 
20. Willardson, J. M. (2007). Core stability train-
ing: applications to sports conditioning programs. 
Journal of Strength and Conditioning Research, 
21(3), 979 – 985. 
 
 
FACULDADE DE CIÊNCIAS DA SAÚDE 
DOUTORADO EM CIÊNCIAS DO MOVIMENTO HUMANO 
 
 
 
PROJETO DE PESQUISA: 
ANÁLISE MIOELÉTRICA DURANTE O EXERCÍCIO ABSWELL EM 
DIFERENTES ÂNGULOS DO OMBRO 
 
Doutorando: Josinaldo Jarbas da Silva 
Doutorando: Mauro Antônio Guiselini 
 
Orientador: Prof. Dr. Paulo Henrique Marchetti 
 
 
 
Projeto de Pesquisa para compor a 
nota da matéria eletromiografia 
aplicada ao estudo do movimento 
humano do Programa de Doutorado 
em Ciências do Movimento 
Humano (UNIMEP). 
 
Piracicaba 
2015 
 
 
2 
SUMÁRIO 
 
SUMÁRIO ................................................................................................................................................... 2 
1 INTRODUÇÃO ........................................................................................................................................ 3 
2 OBJETIVO GERAL: ................................................................................................................................ 3 
2.1 OBJETIVO ESPECÍFICO .............................................................................................................. 4 
3 JUSTIFICATIVA E RELEVÂNCIA ........................................................................................................ 4 
4 MATERIAIS E MÉTODOS ..................................................................................................................... 4 
4.1 PARTICIPANTES ......................................................................................................................... 4 
4.2 PROCEDIMENTOS ......................................................................................................................5 
4.3 AVALIAÇÕES .............................................................................................................................. 5 
4.4 ANÁLISE DOS DADOS ............................................................................................................... 8 
4.5 ANÁLISE ESTATÍSTICA ............................................................................................................. 8 
5 RESULTADOS ......................................................................................................................................... 8 
6 CONCLUSÃO .......................................................................................................................................... 9 
7 REFERENCIAS ........................................................................................................................................ 9 
 
 
 
3 
1 INTRODUÇÃO 
 
A escolha do exercício é parte fundamental do treinamento de força. Os exercícios 
monoarticulares são geralmente utilizados com o objetivo de isolar grupos musculares específicos 
e podem impor menos risco de lesão pela reduzida técnica necessária, entretanto aumentam o 
estresse articular. Por outro lado, exercícios multiarticulares possuem uma maior demanda neural, 
resposta hormonal e são geralmente considerados como mais efetivos quando o objetivo é 
aumentar a força muscular de uma maneira geral pela grande quantidade de sobrecarga levantada 
e massa muscular envolvida, ambos os exercícios (mono e multiarticulares) são efetivos para 
aumentar a força e hipertrofia muscular, portanto devem ser incorporados ao programa de 
treinamento de força (Soares and Marchetti 2013). 
Existem inúmeros exercícios para o desenvolvimento dos músculos que estabilizam a 
articulação do ombro e tronco (particularmente o latíssimo do dorso, peitoral maior, reto do 
abdome e os eretores da coluna), (Marchetti, Calheiros Neto et al. 2007). Dentre estes exercícios, 
o abswell é extensivamente utilizado nos programas de treinamento de força por ser comumente 
utilizados nas salas de musculação. Diversos são os fatores biomecânicos que podem seletivizar 
as atividades musculares durante algum exercício, (Marchetti, Amorim et al. 2010). 
Marchetti et al, (2011) explica que a neuromecânica auxilia na compreensão de como o 
sistema nervoso interpreta a ação articular (torque), e solicita a musculatura específica da forma 
mais eficiente e econômica possível, para isso utilizou o exercício pullover e a técnica chamada 
eletromiografia, que quantifica a ação elétrica muscular por meio de eletrodos dispostos 
superficialmente nos músculos, definindo sua real participação nos movimentos estudados. O 
entendimento destas variações técnicas influência de forma direta na correta prescrição dos 
exercícios durante o treinamento de força, (Marchetti, Amorim et al. 2010). 
 
2 OBJETIVO GERAL: 
 Analisar o padrão de ativação muscular durante o Abswell em diferentes angulações do 
ombro. 
 
 
4 
2.1 OBJETIVO ESPECÍFICO 
Mensurar e comparar a atividade mioelétrica do reto do abdome, peitoral maior, eretores 
da coluna e latíssimo do dorso durante o exercício abswell isométrico em três diferentes posições 
de flexão de ombro (neutra ,90° e 130°), em sujeitos treinados. 
 
 
3 JUSTIFICATIVA E RELEVÂNCIA 
O presente trabalho visará analisar o padrão de ativação muscular durante exercício 
abswell em diferentes posições neutra, 90° e 130° de flexão de ombros. Contribuindo com o 
fornecimento de informações fundamentais para o entendimento de como o sistema 
neuromuscular se adapta as diferentes condições. Essas informações serão importantes para 
auxiliar na montagem dos programas de treinamento de força e nos programas de reabilitações da 
musculatura estabilizadora de ombro e tronco. 
4 MATERIAIS E MÉTODOS 
Trata-se de um estudo transversal, prospectivo, que foi realizado no laboratório de 
Performance Humana da Universidade Metodista de Piracicaba. O presente trabalho objetivou 
analisar o padrão de ativação muscular durante o exercício abswell em diferentes posições neutra, 
90° e 130° de flexão de ombro. 
 
 
4.1 PARTICIPANTES 
 A amostra foi composta por 6 indivíduos do sexo masculino idade 25±3 anos, massa 
corporal 81±2 kg, estatura 178±5 cm, dobra cutânea abdominal 13±6 mm, todos treinados em 
musculação por no mínimo um ano. Os critérios de exclusão adotados foram os seguintes: (i) 
sujeitos não treinados em musculação; (ii) cirurgia prévia em membros superiores ou coluna; (iii) 
qualquer acometimento osteo-mioarticular e ligamentar nos membros superiores e tronco. 
 
 
 
 
5 
4.2 PROCEDIMENTOS 
 Os sujeitos se apresentaram no laboratório em apenas uma sessão que foi dividida em dois 
momentos. Primeiramente, foram obtidos seus dados pessoais por meio de um questionamento 
oral como nome, idade, tempo de prática na musculação. Adicionalmente foram avaliados os 
dados antropométricos como massa corporal, estatura e dobra cutânea abdominal. Em seguida, 
os indivíduos realizaram um breve aquecimento com o exercício abswell que serviu como 
familiarização com os posicionamentos à serem realizados no presente trabalho nas seguintes 
posições (neutra, 90° e 130° de flexão de ombros). 
No segundo momento, os sujeitos foram instrumentados e realizarão o exercício abswell 
nas três condições isométricas por 10 segundos com intervalos de 1 minuto entre cada condição. 
Cada sujeito realizou o exercício abswell nas 3 diferentes angulações de flexão do ombro através 
de uma demarcação feita previamente no solo, sendo que a demarcação foi reposicionada para 
que se ajustasse a estatura específica de cada sujeito. As posições do abswell foram: abswell 
neutra (AWN), abswell em 90° de flexão dos ombros (AW90), e abswell em 130° de flexão de 
ombros (AW130), (Figura1). 
 
 
 
 
4.3 AVALIAÇÕES 
 
 
FIGURA 1. Posicionamento do sujeito durante o abswell isométrico nas posições (a) neutra, (b) 
90° e (c) 130° de flexão de ombros. 
 
 
6 
Eletromiografia Superficial (sEMG): Para a coleta dos dados de sEMG, durante o 
abswell isométrico neutra, 90° e 130° de flexão de ombros foi utilizado um eletromiógrafo EMG 
830 C de 8 canais, da marca EMG System Tecnologia eletrônica, São José dos Campos, Brazil 
com resolução de 16 bits e faixa de entrada de +2V, conectado a um notebook, software 
EMGLAB, com frequência de aquisição de 2000 Hz por canal e filtro passa banda de 20 a 500 
Hz do tipo Butterworth de 4ª ordem. Foram utilizados eletrodos de superfície, simples diferencial 
(Lynx Tecnologia eletrônica, São Paulo, Brazil). Estes eletrodos apresentavam sob a cápsula 
um circuito pré-amplificador com ganho de 20 vezes (±1%), IRMC > 100 dB, e taxa de ruído do 
sinaldo 
músculo. Para a colocação dos eletrodos os pelos da região foram removidos e uma leve abrasão 
foi realizada na pele para remoção das células mortas e redução da impedância. O eletrodo 
 
 
7 
monopolar de referência auto-adesivo, Ag/AgCl com 1cm de diâmetro, associado à um gel 
condutor, foi colocado na proeminência óssea da clavícula. A aquisição dos dados 
eletromiográficos foi feita a uma frequência de 2000 Hz. 
 Visando a normalização dos dados sEMG, os sujeitos permaneceram sentados e 
exerceram uma contração voluntária máxima isométrica (CVMI) específica contra uma 
resistência externa fixa durante 10 segundos, em flexão de ombros para o músculo peitoral maior, 
em extensão de ombro para o músculo latíssimo do dorso, em movimento de extensão máximo da 
coluna para o músculo eretor da coluna e, em flexão isométrica de coluna para o músculo reto do 
abdome. 
 
 
FIGURA 2. Posicionamento dos eletrodos de sEMG nas vistas (a) frontal, (b) posterior e (c) 
lateral. 
 
 
 
8 
4.4 ANÁLISE DOS DADOS 
 
Para a análise do sinal sEMG foram coletados 10 segundos. O primeiro segundo foi 
removido e utilizado apenas os 3 segundos subsequentes, então o processamento seguiu a 
seguinte ordem: os sinais EMG foi filtrado com um filtro de 4a ordem, passa banda entre 20-500 
Hz, e atraso de fase zero. Foi utilizada a root-mean square (RMS) com uma janela de 150 ms, 
para a amplitude do sinal EMG (RMS EMG) que foi normalizado pelo pico da CVMI. Foi 
calculada a área sobre a curva do RMS EMG, definindo-se a sEMG integrada (IEMG). 
 
4.5 ANÁLISE ESTATÍSTICA 
 
A normalidade e homogeneidade das variâncias serão verificadas utilizando o teste de 
Shapiro-Wilk e Levene, respectivamente. Considerando os dados paramétricos, todos os dados 
foram reportados através da média e desvio padrão (DP) da média. Uma one-way ANOVA foi 
realizada para verificar as diferenças entre condições (neutra, 90° e 130° de flexão de ombros) 
para o IEMG. Um post hoc de Bonferroni (com correção) foi utilizado para verificar possíveis 
diferenças. O cálculo do efeito do tamanho (ET) foi realizado através da fórmula de Cohen onde 
os resultados se basearão nos seguintes critérios: 1.5 grande efeito, para sujeitos treinados de forma recreacional 
baseado em Rhea (2004). Significância (α) de 5% foi utilizada para todos os testes estatísticos, 
através do software SPSS versão 18.0. 
 
5 RESULTADOS 
 
Para a IEMG foi verificado uma diferença principal para o reto do abdome (pLe Coguic, DPT1
Lindsey Paprocki, DPT1 
Michael Voight, PT, DHSc, SCS, OCS, ATC, CSCS1
T. Kevin Robinson, PT, DSc, OCS1
CORRESPONDING AUTHOR
Lindsey Paprocki
1351 Emir Street,
Green Bay, WI 54313
E-mail: paprockil@sbcglobal.net
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 207
INTRODUCTION
The lower extremity functions in a kinematic chain, 
leading many researchers in recent years to examine 
the mechanical effect of weak proximal musculature 
on more distal segments.1,2 Previous research by Dis-
tefano,3 Bolgla,4 and Ayotte5 has sought to determine 
the most appropriate exercises to strengthen the glu-
teal muscles due to their role in maintaining a level 
pelvis and preventing hip adduction and internal 
rotation during single limb support.1,6 Measurement 
of such femoral torsion and pelvic rotation in the 
transverse plane, along with measurement of pelvic 
tilt in the sagittal plane can indicate abnormal align-
ment of the hip joint.7 Numerous pathologies have 
been described which are related to the inability to 
maintain proper alignment of the pelvis and the 
femur, including: tibial stress fracture,8 low back 
pain,9,10 iliotibial band friction syndrome,1,11 anterior 
cruciate ligament injury,1,12 and patellofemoral 
pathology.2,13,14,15,16,17 While Distefano,3 Bolgla,4 and 
Ayotte5 have examined a wide range of exercises used 
to strengthen the hip musculature, to the knowledge 
of the authors, no cross comparison amongst the top 
exercises from each study has been performed. 
Similar to Distefano,3 Ayotte,4 and Bolgla,5 exercises 
examined in the current study were rank ordered 
according to their recruitment of specific gluteal mus-
culature and expressed as a percent of the subject’s 
maximum volitional isometric contraction (MVIC). 
By knowing the approximate percentage of MVIC 
(%MVIC) recruitment of each of the gluteal muscles 
in a wide variety of exercises, the exercises may be 
ranked to appropriately challenge the gluteal muscu-
lature. MVIC was established in the standard manual 
muscle testing positions for gluteus medius and maxi-
mus, as described by Daniels and Worthingham.18 The 
use of the sidelying abduction position is supported 
by the results of Widler,19 where similarity in EMG 
activity for weight bearing and sidelying abduction 
(ICC’s 0.880 and 0.902 for the respective positions) 
demonstrated that it is acceptable to use the MVIC 
value obtained during the standard manual muscle 
test position in order to establish a percentage MVIC 
for a weight bearing exercise. 
Several previously published research articles helped 
to establish the parameters for determining a suffi-
cient level of muscle activation for strength gains 
referenced in the current study. Anderson found that 
in order for strengthening adaptation to occur, muscle 
stimuli of at least 40-60% of a subject’s MVIC must 
occur.20 When quantifying muscular strength, work by 
Visser correlates the use of a MVIC and a one-repeti-
tion maximum.21 In order to gain maximal muscular 
hypertrophy, Fry’s work suggests an 80-95% of a sub-
ject’s one repetition maximum must be achieved.22 
Based on the work by Anderson,20 Visser,21 and Fry,22 
for the purposes of this study, exercises producing 
greater than 70%MVIC were deemed acceptable for 
enhancement of strength.
Distefano examined electromyography (EMG) signal 
amplitude normalized values of gluteus medius and 
gluteus maximus muscles during exercises of vary-
ing difficulty in order to determine which exercises 
most effectively recruit these muscles.3 Rank order 
of exercises and %MVIC of Distefano’s study can be 
viewed in Table 1. Of the top five exercises for the 
gluteus medius described by Distefano, the authors 
of the current study chose to reexamine sidelying hip 
abduction, single limb squat, and the single limb 
deadlift. Lateral band walk was not included in the 
current study as the researchers wished to only exam-
ine exercises that required no external resistance. 
Research by Bolgla and Uhl also examined the mag-
nitude of hip abductor muscle activation during reha-
bilitative exercises.4 Their results may be viewed in 
Table 2. Of the exercises studied by Bolgla et al, the 
authors of the current study chose only to look at the 
pelvic drop and sidelying hip abduction. These two 
exercises were chosen since the primary intention 
of the current study was to compare an exercise’s 
recruitment of the gluteal musculature, and not the 
activation effects of weight bearing versus non-weight 
bearing on the musculature.
Finally, Ayotte et al. used EMG to analyze lower 
extremity muscle activation of the pelvic stabilizers 
as well as the quadriceps complex during five unilat-
eral weight bearing exercises,5 displayed in Table 3. 
The authors of the current study elected to forgo ana-
lyzing a single-limb wall squat and a single-limb mini-
squat due to their similarity to the single-limb squat. 
Forward step-up and lateral step-up were included in 
the current analysis. The current study serves to com-
pare top exercises from these previously published 
studies, as well as several other commonly performed 
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 208
informed consent form as well as a health history 
form and comprehensive lower quarter screen to 
identify exclusionary criteria. Pain when performing 
exercises, current symptoms of injury, history of ACL 
injury or any lower extremity surgery within past 
two years, and age of less than 21 years were criteri-
ariteria for exclusion. 
Testing Procedures
EMG data were collected and analyzed on the domi-
nant leg, identified by which leg the subject used to 
kick a ball.3,5,23 Alcohol wipes were used to clean the 
skin over the gluteal region prior to electrode place-
ment. Schiller Blue Surface electrodes (Schiller America 
Inc.; Doral, FL) were placed over the gluteus medius 
and gluteus maximus muscles of the subject’s dominant 
clinical exercises in order to determine the exercises 
that are most effective at recruiting the gluteus maxi-
mus and medius. 
METHODS
Subjects
This study was approved by the Institutional Review 
Board of Belmont University. A total of 26 subjects 
were recruited from within the university and sur-
rounding community through flyers and word of 
mouth. Healthy subjects who were able to perform 
exercise for approximately one hour were included 
in the study and reported to the laboratory for a sin-
gle testing session. At this time they completed an 
Table 1. Findings of Distefano et al.3 Values are described as %MVIC, followed by rank in parentheses.
Table 2. Findings by Bolgla and Uhl,4 represented as 
%MVIC.
Table 3. Findings of Ayotte et al.5 Values are described 
as %MVIC, followed by rank in parentheses.
The International Journal of Sports Physical Therapy | Volume 6, Number 3 | September 2011 | Page 209
procedures are unlikely to be available in a clinic. To 
ensure proper exercise technique, each subject was 
allowed three practice repetitions prior to data collec-
tion and any necessary verbal and tactile cues by the 
instructing researcher. A description of each exercise 
may be found in Appendix A. After completing all 
exercises, the subject’s MVIC was reassessed to ensure 
electrodes had not been displaced during testing.
The equipment used for the conditions which 
required an unstable surface is the Core-Tex Balance 
Trainer™ (Performance Dynamics; San Diego, CA), a 
new piece of exercise equipment which is a platform 
mounted on a half-sphere atop a circular basin lined 
with ball bearings, creating an unstable and rapidly 
accelerating surface (Figure 2). The Core-Tex™ was 
developed to train a healthy fitness population; how-
ever, it may also be used to train individuals during 
rehabilitation in a clinical setting. 
Data Analysis
All data were rectified and smoothed using a root-
mean-square algorithm, and smoothed