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Muscle Hypertrophy Response to Range of Motion in Strength Training: A
Novel Approach to Understanding the Findings
Article  in  Strength & Conditioning Journal · August 2022
DOI: 10.1519/SSC.0000000000000737
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Charlie Ottinger
Barton College
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Matthew H Sharp
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Matthew W Stefan
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Muscle Hypertrophy
Response to Range of
Motion in Strength
Training: A Novel
Approach to
Understanding the
Findings
Charlie R. Ottinger, Matthew H. Sharp, Matthew W. Stefan, Raad H. Gheith, Fernando de la Espriella,
and Jacob M. Wilson
Research Division, Applied Science and Performance Institute, Tampa, Florida
A B S T R A C T
One resistance training variable that may
be altered to achieve desired outcomes
is the range of motion used in training.
Generally, the strength and conditioning
field has accepted that using a greater
range of motion in strength training
exercises results in more substantial
muscle hypertrophy outcomes. How-
ever, this theory has proved to be
inconsistently supported in the literature,
and to date, no sufficient explanation
exists to explain this phenomenon. This
review article seeks to outline a novel
approach for potentially describing the
disparities seen in range of motion
research with respect to hypertrophy
outcomes by applying the unique length-
tension curve of each muscle being
examined. As will be discussed in the
review, virtually all the results from range
of motion studies in various muscles
have corresponded to each muscle’s
length-tension curve; muscles that are
active on the descending limb of the
curve appear to garner greater hyper-
trophy from using larger ranges of
motion. Conversely, muscles that are not
active on the descending limb exhibit
similar adaptations despite alterations in
range of motion. A novel hypothesis for
applying this information to resistance
training programs will be presented and
discussed.
INTRODUCTION
D
esigning safe and effective
strength and conditioning pro-
grams requires careful and
purposeful institution of appropriate
training variables for the desired out-
come. Given that resistance training
adaptations are specific to the mode
or variable of training performed (20),
it is necessary to implement these
variables in a planned fashion specific
to the goals of the athlete or team
performing the program. Common
training variables used in resistance
training programs include repetition
ranges (61), training intensity (39,61),
training frequency (63), contraction
speed emphasized (52,62), loading pat-
terns (33,70), and even the joint range
of motion used (5,19,32,38,55,59,68) in
resistance training exercises.
The range of motion used during resis-
tance training exercises is a unique train-
ing variable in that it affects long-term
adaptations but is also influenced by the
inherent biomechanics and abilities of
the trainee. Indeed, unique individual
anthropometry largely determines the
mechanical challenge imposed by resis-
tance training exercises because these
Address correspondence to Charlie R. Ot-
tinger, cottinger@theaspi.com.
KEY WORDS :
range of motion; length-tension curve;
hypertrophy; muscle length
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Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
mailto:cottinger@theaspi.com
inherent kinesthetic traits largelydictate
the overall range of motion performed at
each joint involved in an exercise (9). In
addition, training experience in both
stretching and resistance training can
improve joint flexibility (41,65) which
leads to an improved ability to withstand
a greater range of motion in strength
training exercises. Finally, the intrinsic
or trained flexibility of a given muscle
can also influence its optimal length for
force production, thus adjusting the
length-tension curve of the muscle (75).
In applied settings, this affects exercise
selection and/or modification as well
as the ranges of motion used.
Researchers can measure strength
training range of motion through a
small variety of tools. The primary mea-
surement method has centered on assess-
ing the degrees of rotation performed at a
specific joint (5,19,32,38,55,68). In addi-
tion, resistance implement displacement
has also been used in research (26) albeit
to a lesser extent. Ultimately, joint range
of motion is likely the most common
method of measurement because this cal-
culation is more relevant to the training
stimulus a givenmuscle may receive in an
exercise. This is due to the relationship
between the range of motion performed
at a joint and the concomitant length
change of each muscle that interacts with
the joint (51).
Indeed, previous studies have consis-
tently used greater ranges of motion or
deeper positions of joint flexion to assess
muscles at “long” lengths, whereas short-
er ranges of motion or more shallow
joint angles represent “short” muscle
lengths (19,37,38,47,55,57,59). Certainly,
the change in joint angle does not per-
fectly correlate with a change in muscle
length because this relationship can be
affected by muscle activation (48,64),
contraction/movement velocity (43),
and muscle pennation angle and resul-
tant architectural gear ratios (64). How-
ever, the pursuit of ecological validity
reigns supreme in the field of applied
strength and conditioning, and joint
range of motion remains the primary
way of dictating training with “long” or
“short” muscle lengths. Because ultraso-
nography is necessary to truly measure
muscle length (25,68), this tool is rarely
used in strength and conditioning set-
tings. One important distinction is that
the specific joint degrees used in various
ranges of motion are not interchange-
able. Indeed, moving from 0 to 508 of
elbow flexion involves the same absolute
range of motion as 50–1008 elbow flex-
ion; however, the 0–508 range would
certainly be considered a longer length
than the 50–1008 range. Regardless, in
many applied strength and conditioning
studies, the terms “range of motion” and
“muscle length” are almost used inter-
changeably in which greater ranges of
motion refer to greater muscle lengths
and vice versa.
With this application in mind, Bloomquist
et al. (5) and McMahon et al. (38) found
that greater ranges of motion at the knee
were more effective at inducing muscle
hypertrophy in the quadriceps muscle
group; however, Pinto et al. (55) discov-
ered that partial range of motion elbow
flexion training was just as effective at pro-
moting muscle hypertrophy in the biceps
as full range of motion training. It is gen-
erally accepted that full range of motion
training is likely optimal for muscular
development, but this paradigm has been
met with contrary findings from Pinto
et al. (55) and both Goto et al. (19) and
Stasinaki et al. (68) who found similar lev-
els of triceps hypertrophy after training
with full or partial elbow extension ranges
of motion. Furthering the confusion,
recent research from Maeo et al. (37)
uncovered that seated knee flexion train-
ing produced greater hypertrophic adap-
tations in the hamstrings compared with
prone knee flexion training. Because the
hamstrings are a biarticulate muscle group
that crosses both hip and knee joint, the
seated knee flexion variation lengthens the
hamstrings to a greater degree (36), thus
imposing a greater range ofmotion for the
hamstrings.
Although the aforementioned research
into the range of motion used during
resistance training exercises has pro-
duced unclear results, the mechanism
through which these adaptations take
place may not be as simple as previously
believed. The weight of the research has
begun to show that different muscle
groups adapt uniquely to different ranges
of motion which warrants further theo-
retical investigation to explain this phe-
nomenon. Therefore, the purposes of
this article were to (a) review the process
of muscle hypertrophy and how muscle
length can affect hypertrophic adapta-
tions, (b) analyze previous findings
related to range of motion and muscle
hypertrophy, and (c) introduce a novel
theory for explaining these occasionally
contrary findings.
MUSCLE HYPERTROPHY
Because muscle hypertrophy is a pri-
mary outcome in many range of
motion studies, a brief review of this
phenomenon is necessary. Muscle
hypertrophy is the procedure through
which a muscle fiber undergoes a re-
modeling process which, in turn,
results in a larger muscle fiber. Muscle
hypertrophy can occur through at
least 3 unique morphological pro-
cesses, including sarcoplasmic hyper-
trophy, myofibrillar hypertrophy, and
longitudinal hypertrophy.
Sarcoplasmic hypertrophy is typically
referred to as an increase in cellular sar-
coplasm or sarcoplasmic components
which results in the expansion of the
overall volume of the muscle fiber
(22,58). Previously, it was believed that
endurance or interval training had a
greater association with sarcoplasmic
hypertrophy because of an increase in
muscle glycogen storage; however,
recent research from Haun et al. (21)
uncovered that resistance training can
also induce sarcoplasmic hypertrophy,
even to a disproportionate ratewithmyo-
fibrillar hypertrophy which is more often
associated with resistance training.
Although the exact mechanism that pref-
erentially induces sarcoplasmic hypertro-
phy over myofibrillar hypertrophy is
unclear, sarcoplasmic hypertrophy plays
at least a minor role in hypertrophic
adaptations to resistance training (58).
Myofibrillar hypertrophy is the most
common type of muscle hypertrophy
associated with resistance training.
This is seen in both acute studies in
which myofibrillar protein synthesis
rates increase after resistance training
Muscle Hypertrophy Response
VOLUME 00 | NUMBER 00 | MONTH 20222
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
(13) and longitudinal studies in which
trained subjects exhibit higher levels of
myofibrillar proteins than untrained
individuals (72). Myofibrillar hypertro-
phy occurs through an increase in
myofilament packing density, or more
simply put, an increase in the abun-
dance of contractile proteins within
the myofibril (58). Ultimately, this
structural adaptation increases the
overall diameter of the muscle fiber.
It is posited that myofibrillar hypertro-
phy is mostly associated with resis-
tance training because it is highly
related to the force producing ability
of a muscle (69). Therefore, the most
prominent mechanism through which
myofibrillar hypertrophy occurs is
likely resistance training.
Longitudinal hypertrophy is displayed
through a lengthening of the myofibril.
Previously, researchers understood this
change in length to be a result of an
increase of sarcomeres in series, which
would effectively lengthen the muscle
fiber (15). However, more recent
research has highlighted that an
increase of sarcomeres in series is not
necessary to elicit longitudinal hyper-
trophy (54), so further research is cer-
tainly needed to further understand
this form of muscle hypertrophy.
Regardless, this unique adaptation is
believed to be preferentially induced
during eccentric contractions or even
active and passive stretching in which a
muscle experiences tension at long
muscle lengths. Mechanistically, longi-
tudinal hypertrophy may be a protec-
tive adaptation to better produce force
at long muscle lengths (16,40); how-
ever, furtherresearch is needed to ver-
ify this theory. Moreover, the visual
microscopic representation of longitu-
dinal hypertrophy can be difficult to
quantify (29), thus increasing the need
for further exploration into this topic.
LENGTH-TENSION CURVE AND
RESISTANCE TRAINING
APPLICATIONS
LENGTH-TENSION CURVE
Although the relationship between
potential hypertrophic stimuli and
observed muscle hypertrophy is not
fully understood, it is well accepted
that mechanical tension is likely the
primary driver of myofibrillar and lon-
gitudinal hypertrophy (74). Mechani-
cal tension is detected by
mechanoreceptors within the muscle
that, in essence, measure muscular
force production through deformation
of their plasma membrane. After detec-
tion of sufficient force, mechanorecep-
tors create electrical and chemical
signals that begin the protein remodel-
ing process that results in muscular
hypertrophy (6,74). However, the
route of mechanical tension detection
that stimulates longitudinal hypertro-
phy may be unique.
In 1954, Huxley and Niedergerke (27)
published the first ever report that
detailed findings related to microscopic
analysis of living muscle fibers. This
article was shortly followed by a similar
article from Huxley and Hanson (28).
The combination of these articles led
to the birth of the sliding filament the-
ory, which suggested that muscles con-
tract using 2 proteins, actin and myosin,
“sliding” past one another. However,
this theory did not explain every aspect
of muscular contraction; factors such as
residual force enhancement and passive
force production were difficult to
explain through this model (34). More
recent research has proposed an update
to the sliding filament theory: the wind-
ing filament theory. The winding fila-
ment theory builds on the sliding
filament theory but fills the gaps
through the inclusion of the giant pro-
tein, titin. As the theory’s name sug-
gests, titin “winds” itself around the
contractile protein, actin, during length-
ening contractions and then releases
stored energy like a spring during short-
ening contractions (16,45,46,66).
Intriguingly, titin in and of itself is a type
of mechanoreceptor that detects
mechanical tension. Owing to the
spring-like action of titin, various aspects
of its winding and unfolding process
sense mechanical loading much like
the aforementioned mechanoreceptor
(31). Titin’s mechanosignaling process
differs from mechanoreceptors through
unique pathways and downstream
signaling molecules, but the end process
of this signaling cascade results in protein
remodeling that ultimately leads to mus-
cle hypertrophy (35). A second distinc-
tive factor of titin is that its resultant
signaling cascade is likely greatest during
muscle contractions performed in a
stretched or lengthened position (42).
This unique aspect of titin has been the-
orized to be a determinant of the greater
hypertrophic adaptations occasionally
seen with longer range of motion train-
ing (31) because these ranges will impose
greater length changes on the muscle.
However, this theory is highly related
to the next topic worthy of discussion:
the length-tension curve.
The length-tension curve visualizes the
relationship between tension (or force)
and sarcomere length (36) as shown in
Figure 1. Sarcomeres are the individual
contractile units within a single myofi-
bril; muscle lengthening or shortening
is dictated by the collective change of
length of the sarcomeres within a sin-
gle fiber. Practitioners often use this
length-tension curve in tandem with
the working range of motion of the
primary joint a muscle acts on (56).
The length-tension curve contains 3
unique components: the ascending limb,
the plateau portion, and the descending
limb. The plateau portion of the length-
tension curve is associated with sarco-
mere lengths near the resting value.
The ascending limb, then, represents
shorter sarcomere lengths, whereas the
descending limb depicts longer sarco-
mere lengths. As shown in Figure 1,
the ascending and descending limbs of
the length-tension curve are generally
associated with increasing and decreas-
ing force production, respectively. How-
ever, the plateau portion of the length-
tension curve displays the optimal force
producing length for a muscle (36).
Therefore, the astute practitioner would
theoretically be correct in assuming that
training a muscle near its resting length
would be optimal for muscle hypertro-
phy because of peak force production
occurring near this position.
However, the simple length-tension
curve does not account for passive
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elements, such as titin, that can also
contribute to muscle force production.
Thus, an adjusted length-tension curve
is shown in Figure 2 in which passive
elements, such as titin, muscle fascia,
and tendons, also contribute to the
total tension developed by the mus-
cle (24).
A perusal of the adjusted length-
tension curve now allows the practi-
tioner to theorize that long sarcomere
lengths are associated with the highest
muscle forces because the combination
in active and passive force likely sur-
passes the peak of the plateau region
(24). This unique finding has likely
driven the strength and conditioning
field to generally accept that a larger
range of motion is more effective for
optimal muscle development than a
shorter range because a large joint
range of motion will induce the great-
est overall length change in the mus-
cles acting on the joint (50,56). The
practice of continually maximizing ten-
sion through using a full range of
motion, then, should lead to greater
hypertrophic gains over a long-term
training program (5,32,38).
However, a proverbial speed bump
appears when attempting to generalize
this theory to all the major muscle
groups used in sport or fitness training.
Intriguingly, not every muscle is active
on all portions of the length-tension
curve. Therefore, training adaptations
to differing ranges of motion and asso-
ciated muscle lengths are likely unique
to the muscle group being trained.
This can explain the discrepancy in
findings between Bloomquist et al. (5)
and Pinto et al. (55). Bloomquist et al.
(5) found that deep squat training (0–
1208 knee flexion) led to greater
hypertrophy in the quadriceps muscle
group (4–7% increase in CSA vs. 0%)
than shallow squat training (0–608 knee
flexion), whereas Pinto et al. (55) found
no significant difference in biceps
hypertrophy (9.65 6 4.4% increase in
muscle thickness vs 7.83 6 4.9%) after
training programs with either a full (0–
1308 elbow flexion) or partial (50–1008
elbow flexion) range of motion,
respectively. Although these findings at
first seem contradictory to the general
theory of full range of motion training,
they may be explained rather simply.
The quadriceps is primarily active on
the descending limb of the length-
tension curve (67) as shown in Figure 3.
Therefore, using a greater range of
motion at the knee during quadriceps
exercises will likely result in greater
hypertrophic adaptations because this
muscle group experiences greater ten-
sion at longer lengths. However, the
biceps brachii is only active on the
ascending portion of the curve (30) as
shown in Figure 4. Therefore, the
biceps is not active on the descending
portion of the length-tension curve and
receives no additional tension-related
benefits from developing force at
longer muscle lengths.
Owing to the potential relationship
between the length-tension curve and
adaptations to differing ranges of
motion in strength training, it is worth
reviewing how altering the range of
motion used in an exercise has been
shown to affect long-term hypertro-
phic adaptations in a variety of muscle
groups.
QUADRICEPS
Kubo et al. (32) examined 17 young
men (20.76 0.4 years) performing deep
squat (0–1408 knee flexion) or half squat
(0–908 knee flexion) training for 10
weeks. Both groups trained2x/week
during this period and followed a linear
program in which training intensity
increased each week. After the 10-week
training program, the authors usedMRI
technology to assess the change in
quadriceps, adductor, hamstrings, and
Figure 1. Length-tension curve. From Lieber et al. (36).
Figure 2. Adjusted length-tension curve. From Herzog (24), with permission.
Muscle Hypertrophy Response
VOLUME 00 | NUMBER 00 | MONTH 20224
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
gluteus maximus cross-sectional area
(CSA). Intriguingly, increases in quadri-
ceps CSA were similar between groups
(4.9 6 2.6% in full squats vs 4.6 6 3.1%
in half squats), whereas increases in
adductor CSAwere significantly greater
in the full squat group than the half
squat group (6.2 6 2.6% vs. 2.7 6
3.1%; p 5 0.026) as were changes in
gluteus CSA (6.7 6 3.5% vs 2.2 6
2.6%; p 5 0.008).
At a glance, (32) the findings of Kubo
et al. regarding quadriceps hypertrophy
in half squats seem at odds with the
results from Bloomquist et al. (5) in
which partial squats were shown to
not induce hypertrophy in the quadri-
ceps. Both studies used untrained sub-
jects; however, Bloomquist et al. (5)
had participants squat to a knee flexion
angle of 608, whereas Kubo et al. (32)
used a knee flexion angle of 908 in the
half squat group. In addition, the study
by McMahon et al. (38), discussed in
further detail below, used a knee angle
of 508 in short range of motion training
and found that this range of motion was
less effective for promoting quadriceps
hypertrophy than using a knee angle of
908. Because the quadriceps is primarily
active on the descending portion of the
length-tension curve (67), it would
appear that 908 of knee flexion is suffi-
cient for increasing total tension and,
therefore, hypertrophy in the quadriceps;
however, further investigation is certainly
warranted to confirm this theory.
McMahon et al. (38) used 26 untrained
and healthy subjects aged 19.0 6 3.4
years in an investigation seeking the
effects of full training programs involv-
ing either a long range of motion (0–
908 knee flexion) or a short range of
motion (0–508 knee flexion) quadriceps
exercises. Participants performed their
respective training programs 3x$wk21
for 8 weeks, and muscle CSA of the
quadriceps was measured before and
after the training program at 25, 50,
and 75% of femur length. The long
range of motion group exhibited sig-
nificantly greater increases in vastus
lateralis CSA at 75% femur length as
opposed to the short range of motion
group (59 6 15% vs 16 6 10%; p ,
0.05) after the 8-week training pro-
tocol. Intriguingly, both groups made
similar (p . 0.05 between groups)
increases in vastus lateralis CSA at 25%
(33.83 vs. 19.04% long range vs. short
range, respectively) and 50% femur
length (18.00% for both groups).
In addition, muscle fascicle length was
measured at 25, 50, and 75% of femur
length. Significant differences between
groups were found for fascicle lengths
measured at 50% femur length (23 6
5% vs. 10 6 2%; p , 0.05) and 75%
femur length (19 6 3% vs. 11 6 2; p
, 0.05), both of which favored the long
range of motion training group. Owing
to the quadriceps position on the de-
scending region of the length-tension
curve, these results are not surprising.
Moreover, these data may present fur-
ther evidence for longitudinal hypertro-
phy because both training groups
exhibited significant increases in muscle
fascicle length. However, the long range
of motion training group experienced
even greater changes in fascicle length
than the short range of motion group.
Another more current study per-
formed by Pedrosa et al. (53) sought
to examine the effects of multiple
ranges of motion in the knee extension
exercise on quadriceps adaptations.
The authors used 45 untrained women
and split these subjects into 4 groups: a
full ROM (100-308 knee flexion), an
initial partial ROM (100-658), a final
partial ROM (65-308), and a varied
ROM which alternated the initial and
final partial ROM conditions. Similar
to other investigations, rectus femoris
(RF) and vastus lateralis (VL) muscle
hypertrophy adaptations were mea-
sured at 70, 60, 50, and 40% femur
length. Intriguingly, the initial ROM
group exhibited the greatest RF and
VL hypertrophy at 70% femur length
(32% & 19%, respectively, vs. 24% & 1
and 19% & 12% for final partial and full
ROM, respectively) and presented with
greater hypertrophy at 60% (24% & 15
vs. 6% & 5.5 and 18% & 13%) and 50%
(28% & 16 vs. 13% & 11 and 13% &
14%) of femur length relative to the
final partial ROM and full ROM
groups. An even more interesting note
is that the final partial ROM group dis-
played similar changes to a nontraining
control group about RF and VL hyper-
trophy at 60% (6% & 5.5 vs. 2% & 2%)
and 70% (24% & 1 vs. 1% & 2%) femur
length. This study further emboldens
the theory that the quadriceps muscle
group responds more favorably to
training at long muscle lengths when
hypertrophy is the desired training out-
come. Again, this theory is likely
dependent on the length-tension curve
Figure 3. Length-tension relationship of the vastus lateralis. Adapted from Son et al.
(67) with permission.
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of the quadriceps which favors
increased tension at longer muscle
lengths.
TRICEPS
Investigations from Goto et al. (19)
and Stasinaki et al. (68) found differing
results from Bloomquist et al. (5),
McMahon et al. (38), Kubo et al.
(31), and Pedrosa et al. (53) when as-
sessing ranges of motion used in train-
ing the triceps brachii. Goto et al. (19)
split 44 resistance trained men aged
21.6 6 1.3 years into 2 groups, one of
which performed partial (45–908 elbow
flexion) elbow extension training and
the other performed full (0–1208 elbow
flexion) elbow extension training. Each
group trained their respective range of
motion 3x/week for 8 weeks while
following a protocol of 3 sets of 8 at
their 8RM load. Curiously, triceps CSA
increased to a greater extent (p , 0.05)
after partial range of motion training
(48.76 14.5%) as opposed to full range
of motion training (28.2 6 10.9%).
Goto et al. (19) theorized that the
greater hypoxia experienced during
partial range of motion training may be
the mechanism at work because the
authors reported a correlation of
r 5 0.70 between an increase in CSA
and time spent under the oxygen-
hemoglobin dissociation curve. Intrigu-
ingly, muscle activation was also higher
in the partial range of motion condition
(p , 0.05 between groups) which
could certainly have affected hypertro-
phic adaptations. However, these
components may not be the only
mechanisms influencing this outcome.
Stasinaki et al. (68) also examined
unique triceps training methods, albeit
in a group of 9 untrained women aged
19.3 6 0.4 years. Each participant
trained one arm with a long muscle
length range of motion (70–1508
elbow flexion) and the other with a
short range of motion (10–908 elbow
flexion). Participants performed the
training protocol 2x/week for 6 weeks,
and both protocols involved perform-
ing 6 sets of 6 repetitions at 85% 1RM
in the assigned range of motion. After
the training period, both arms experi-
enced significant, but not different (p5
0.618), changes in muscle thickness in
which the long length arm increased
by 13.7 6 9.0% and the short length
arm increased by 10.7 6 15.3%. A key
aspect of this particular study is that
ultrasonography was also used to val-
idate the ranges of motion used with
respect to muscle length of the long
head of the triceps. In the long muscle
length condition, subjects performed
overhead triceps extensions which
produced a range of fascicle lengths
from 60.1 6 7.7 to 66.5 6 4.8 mm.
Conversely, the short range of motion
training condition generated a range of
fascicle lengths from 44.2 6 5.9 to 51.3
6 4.8 mm. Fasciclelength was deter-
mined to be statistically different (p ,
0.05) between groups which certainly
aids in the theoretical applicability of
this study’s findings.
Ultimately, the length-tension curve
still seems to apply in both the Goto
et al. (19) and Stasinaki et al. (68) stud-
ies. Previous research has found that
the triceps is primarily active in the
plateau region of the length-tension
curve (44). Therefore, the triceps pro-
duces similar levels of force regardless
of muscle length and, thus, would the-
oretically experience similar hypertro-
phic adaptations in either short or long
ranges of motion.
GLUTEUS
Recent research from Barbalho et al.
(3) sought to examine the hypertrophic
adaptations of the gluteus maximus
after either deep squat (0–1408 knee/
hip flexion) training or barbell hip
thrust training (90-08 hip flexion)
which inherently includes less hip and
knee range of motion compared with
the deep squat. The authors split 22
trained women into 2 different training
groups that trained 2x$wk21 for 6
weeks. After the training intervention,
average gluteus maximus muscle
thickness increased by 9.4% in the deep
squat group and 3.7% in the hip thrust
Figure 4. Length-tension relationship of the biceps brachii. Adapted from Koo et al. (30), with permission.
Muscle Hypertrophy Response
VOLUME 00 | NUMBER 00 | MONTH 20226
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
group (p 5 0.001 between groups),
thus suggesting that the gluteus max-
imus responds well to training at longer
muscle lengths. As previously men-
tioned, the Kubo et al. (32) squat study
found that deep squat training
enhanced gluteus muscle volume by
6.7 6 3.5%, whereas half squat training
only increased gluteus volume by 2.26
2.6%. Moreover, Nakamura et al. (45)
investigated subjects performing fly-
wheel squats to 90 degrees of knee
flexion 2x/week for 5 weeks and found
no significant changes (p . 0.05) in
gluteus maximus muscle thickness,
whereas Yasuda et al. (76) found that
full ROM leg press (90-08 knee flexion
and 125-708 hip flexion) training for 12
weeks resulted in a 4.4% increase in
gluteus muscle thickness.
Although the length-tension relation-
ship of the gluteus maximus is currently
unknown, the above findings from Bar-
balho et al. (3), Kubo et al. (32), Naka-
mura et al. (45), and Yasuda et al. (76)
would suggest that the gluteus is likely
active on the descending portion of the
length-tension curve and that a greater
hip flexion angle will likely induce
greater hypertrophic adaptations than
a shallow hip flexion angle. In addition,
Contreras et al. (11) discovered that the
gluteus exhibits maximal activation in
the top region of the barbell hip thrust
exercise which suggests that the gluteus
likely is not active on the ascending
portion of the curve. Muscles that are
active on the ascending portion of the
curve often exhibit a trait known as
“active insufficiency” in which they
shorten to a degree in which little force
production is taking place (60). This is
exhibited in studies in which the gas-
trocnemius, a biarticulate muscle well-
known to experience active insuffi-
ciency, displays a reduction in muscle
activation during ankle plantar flexion
with a flexed knee (23).
Worthy of mention, the results of the
Barbalho et al. (3) study are currently
under scrutiny in a white paper sub-
mitted by Vigotsky et al. (73) to the
journal, SportRxiv. Although the article
by Barbalho et al. (3) faces potential
retraction, its results do not disagree
with the findings from Kubo et al.
(32) in which the gluteus maximus dis-
played significantly greater hypertro-
phic adaptations to training with
longer muscle lengths. Future research
is warranted to truly uncover the
length-tension relationship of the glu-
teus maximus because these findings
are of great interest to sport athletes
and physique athletes alike.
BICEPS
A recent project from Sato et al. (59)
slightly mirrored that of Pinto et al.
(55) in which elbow flexor muscle thick-
ness was assessed before and after 2
unique biceps training programs. Sato
et al. (59) recruited 32 male and female
university students and divided them
into 3 groups: a control group, a long
muscle length group (0–508 elbow flex-
ion; full elbow extension was considered
08 flexion), and a short muscle length
group (80–1308 elbow flexion). Both
training groups performed preacher curls
for 3 sets of 10 repetitions in a pro-
gressive loading fashion specific to
maximal isometric strength at the joint
position trained by each group. Training
sessions were performed twice per week
for 5 weeks and outcome measures
consisted of eccentric, concentric, and
isometric torque as well as muscle
thickness at 50, 60, and 70% of the
humerus length between the lateral ep-
icondyle and the acromion.
Although Pinto et al. (55) found similar
muscle hypertrophy adaptations
between ranges of motion for the biceps,
Sato et al. (59) reported that the long
muscle length group made significantly
greater average gains in muscle thickness
than the short muscle length group (8.9
6 3.9 vs. 3.4 6 2.7%; p , 0.01). At first,
these results may seem at odds with the
findings of Pinto et al. (55). However,
subjects in the short muscle length group
designed by Sato et al. (59) performed
biceps curls from 80 to 1308 of elbow
flexion, whereas the subjects in the Pinto
et al. (55) study used an elbow flexion
range of 50–1008. Therefore, it is plau-
sible that training the biceps in the
shortened range seen in the study by
Sato et al. (59) may result in active
insufficiency in the biceps and impaired
hypertrophic adaptations, whereas the
50–1008 range used by Pinto et al. (55)
may not. Certainly, more evidence is
needed to verify this theory.
A related, but unique, study from
Nunes et al. (49) examined the effect
of maximal load placement with
respect to muscle length, rather than
altering the range of motion in an exer-
cise. The authors examined 35 healthy
adults aged 23.7 6 5.3 years perform-
ing either free weight preacher curl or
cable preacher curl training. Both
groups performed full range of motion
training; however, the free weight
training group, because of the inherent
biomechanics of the exercise, would
achieve peak tension at longer muscle
lengths, whereas the cable training
group would attain the highest tension
with the muscle in a shortened state.
After 10 weeks of thrice weekly train-
ing, it was found that both groups
experienced similar increases in biceps
muscle thickness (7% for cable; 8% for
free weights; p 5 0.346), thus strength-
ening the theory that the biceps need
no emphasis on training at longer mus-
cle lengths to maximize hypertrophy.
Another curious study from de Vas-
concelos Costa et al. (14) compared 2
groups of untrained men performing
either a nonvaried or a varied exercise
program 3x$wk21 for 9 weeks. The
researchers then investigated changes
in MTat the proximal, medial, and dis-
tal sites of the major muscle groups
trained throughout the intervention.
A key difference between groups about
biceps training was that the nonvaried
group solely performed traditional bar-
bell curls, whereas the varied exercise
group performed barbell curls,
preacher curls, and incline dumbbell
curls, which could certainly increase
the trained muscle length of the biceps
because of slight shoulder extension
during the incline curl. Both groups
exhibited significant changes in biceps
MT from pre to post for both the
medial (2.2 vs. 3.1%; nonvaried vs. var-
ied, respectively) and distal sites (3.5 vs.
3.7%); however, only the varied exer-
cise group displayed a significant
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increase in proximal biceps MT (2.1 vs.
4.5%). Intriguingly, there were no sig-
nificant between groups differences for
any of the sites measured, even the
proximal biceps (p 5 0.15).These
results suggest that there may be sup-
porting evidence for the inclusion of
biceps exercises with greater shoulder
extension angles; however, further
research is needed.
HAMSTRINGS
Maeo et al. (37) investigated the effects
of 12 weeks of seated or prone knee
flexion training on 20 healthy adults aged
23.5 6 1.6 years. Participants performed
seated leg flexions on one leg and prone
leg flexions on the other. Both exercises
involved a knee range of motion from
0 to 908; however, the seated leg curl
also included a position of 908 of hip
flexion, whereas the prone leg flexion
condition involved 308 of hip flexion.
After the intervention, it was found
that the leg performing seated knee
flexion training experienced a greater
increase in muscle volume in 3 of the
4 hamstrings muscles than the group
performing prone knee flexion training
(14 vs. 9%; p # 0.010). Intriguingly,
both groups exhibited a similar
increase in the monoarticulate biceps
femoris short head muscle (10 vs. 9%;
p 5 0.190). Because 3 of the 4 heads of
the hamstrings are biarticulate (semite-
ndinosus, semimembranosus, and
biceps femoris long head), these mus-
cles are active on the plateau and de-
scending regions of the length-tension
curve (37,75), and thus, they likely
respond greater to training at long
muscle lengths. However, the biceps
femoris short head is a monoarticulate
Figure 5. Length-tension relationship of the latissimus dorsi. Adapted from Gerling and Brown (18), with permission.
Figure 6. Length-tension relationship of the pectoralis. Adapted from Garner and Pandy (17), with permission.
Muscle Hypertrophy Response
VOLUME 00 | NUMBER 00 | MONTH 20228
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
muscle because it only crosses the knee
joint. Therefore, although the biceps
femoris short head is also active on
the plateau and descending regions of
the length-tension curve (37,75), hip
flexion (as occurs in seated knee flexion
training) would have little influence on
the length change in this muscle.
OTHER MUSCLE GROUPS
Although a small number of previous
studies have endeavored to explore the
unique adaptations to altering the
range of motion used in strength train-
ing exercises, not every major muscle
group has been examined. Thus, this
section serves to create a theoretical
basis for application and provide
routes for future research.
Previous research has uncovered that
the latissimus dorsi is active on both
the plateau and descending regions of
the length-tension curve (18) which
would suggest that the latissimus dorsi
is best trained at long muscle lengths;
however, further research is needed to
verify this theory. The length-tension
relationship of the latissimus dorsi is
shown in Figure 5.
Previous research from Garner and
Pandy (17) indicates that the pectoralis
major is active on all portions of the
length-tension curve. Thus, it is likely
optimal to train this muscle group at
longer muscle lengths because the pecto-
rals may experience active insufficiency at
shorter muscle lengths; however, these
theories require further validation in
research settings. The length-tension
relationship of the pectoralis is shown
in Figure 6.
It is known that the deltoid muscle
group contains 3 unique muscle heads,
and intriguingly, the posterior head
displays a unique length-tension curve
compared with the other 2 heads of
the deltoid. Indeed, research from Gar-
ner and Pandy (17) suggests that all 3
heads of the deltoid muscle are active
in the ascending and plateau region of
Figure 7. Length-tension relationship of the deltoid major. Adapted from Garner and Pandy (17), with permission.
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the curve; however, only the anterior
and lateral deltoid reach the descend-
ing portion of the curve. Therefore, it is
likely that the posterior head of the
deltoid need not be trained at longer
muscle lengths for optimal hypertro-
phy because its length-tension curve
is similar to that of the biceps brachii
(30). Similar to nearly every other mus-
cle group, further research is needed to
verify this hypothesis. The length-
tension relationship of the deltoids is
shown in Figure 7.
Research has uncovered that all regions
of the trapezius muscle are active on the
ascending and plateau regions of the
length-tension curve but not the
descending portion (17). Although
purely theoretical, it is certainly plausible
that the trapezius group need not be
trained at longer muscle lengths to
achieve optimal hypertrophic adapta-
tions, but this theory remains undis-
turbed in the research field. The
length-tension relationship for the trape-
zius major is shown in Figure 8.
The final major muscle group that is of
interest to both fitness enthusiasts and
athletes alike is the triceps surae. The
triceps surae consist of the biarticulate
gastrocnemius and monoarticulate
soleus muscles. Owing to their inherent
differences in anatomy, each muscle dis-
plays a unique length-tension curve.
Research from Chen and Delp (8) found
that the soleus is only active on the pla-
teau and descending regions of the
length-tension curve. Conversely, previ-
ous studies have reported that the gas-
trocnemius is only active on the
ascending and plateau portions of the
curve (25). The position of the gastroc-
nemius on the length-tension curve likely
explains its active insufficiency during
combined knee flexion and ankle plantar
flexion movements (23). These data
would suggest that the soleus muscle
responds more favorably to using larger
ranges of motion, whereas the gastroc-
nemius should be primarily trained
through heel raise variations without
Figure 8. Length-tension relationship of the trapezius major. Adapted from Garner and Pandy (17), with permission.
Muscle Hypertrophy Response
VOLUME 00 | NUMBER 00 | MONTH 202210
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
simultaneous knee flexion. The length-
tension relationships of the soleus and
gastrocnemius are shown in Figure 9.
PRACTICAL APPLICATIONS
Although research investigating the
long-term hypertrophic effects of using
different ranges of motion in strength
training exercises is limited, a clear
trend is certainly appearing that
matches a muscle group’s long-term
adaptations with its length-tension
curve with respect to the ranges of
motion used to train it. Indeed, neither
the biceps (55) nor triceps (19,68) gar-
nered additional benefits from using
greater ranges of motion in strength
training. Given that neither muscle
group is active on the descending
region of the length-tension curve, it
is plausible that the range of motion
used for training these muscles is not
as important a training variable as
other overload strategies. Conversely,
research investigating the quadriceps
(5,38) and hamstrings (37) shows that
both muscle groups display a more sig-
nificant hypertrophy response to train-
ing with larger ranges of motion.
Because both muscle groups are active
on the descending portion of the
length-tension curve, these muscles
likely experience greater tension at
long lengths, thus increasing the hyper-
trophic stimulus from training with
larger ranges of motion.
This connection between concepts is
certainly preliminary and requires fur-
ther research; however, it provides
support for using a muscle’s known
length-tension properties and its rela-
tionship with joint ranges of motion to
design resistance training programs for
optimizing muscular hypertrophy. Cer-
tainly, the relationship between joint
angle and muscle length needs further
validation (and is influenced by a vari-
ety of factors), but the strength and
conditioning professional has limited
resources for pursuing an applicable
method of measuring muscle lengths
during strength training exercises.Therefore, it is plausible that practi-
tioners may prescribe greater joint
ranges of motion to induce longer mus-
cle lengths and optimally develop mus-
cle groups that are active on the
descending portion of the length-
tension curve. Unfortunately, the above
studies are the only inquiries into range
of motion and long-term hypertrophic
adaptations in resistance training.
The theoretical connection between con-
cepts presented in this article is
Figure 9. Length-tension relationships of the soleus and gastrocnemius. Adapted from Chen and Delp (8) and Hoffman et al. (25),
respectively.
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undoubtedly preliminary and requires
further research. However, it provides
support for using a muscle’s known
length-tension properties to design resis-
tance training programs for optimizing
muscular hypertrophy. Unfortunately,
minimal studies have been performed
investigating the effects of range of
motion on muscle hypertrophy out-
comes.Moreover, these studies have been
performed on different muscle groups
with unique length-tension curves; thus,
muddying the oft-accepted theory that
greater range of motion will result in
superior muscle hypertrophy relative to
smaller ranges of motion. Despite these
setbacks, research into the length-tension
relationship of nearly every major muscle
group has been performed and Table 1
summarizes these findings.
CONCLUSION
Although preliminary, it is conceiv-
able that applying a given muscle’s
length-tension relationship to the
joint ranges of motion used in resis-
tance training programs may opti-
mize hypertrophic adaptations. At
the very least, this strategy could
improve exercise selection for a
given muscle group and reduce time
spent on emphasizing ranges of
motion that may be inconsequential
to long-term outcomes. This senti-
ment is underscored by research
from Baroni et al. (4) in which full
Table 1
Summary of L-T relationship for major muscle groups
Muscle group Ascending Y/N Plateau Y/N Descending Y/N Applications References
Gastrocnemius Yes Yes No May not necessitate training at longer
lengths. Experiences active insufficiency
at short lengths.
(23,25)
Soleus No Yes Yes Likely experiences greater hypertrophy at
longer muscle lengths.
(8)
Quadriceps No Yes Yes Research has demonstrated greater
hypertrophy at greater lengths. Cutoff
may be at 908 knee flexion.
(5,32,38,53,67)
Hamstrings No Yes Yes All hamstrings muscles likely experience
greater hypertrophy at longer muscle
lengths.
(37,75)
Gluteus
maximus
No* Yes* Yes* Research has demonstrated that the
gluteus maximus responds more
favorably to large ROM training. True
length-tension relationship unknown.
(3,32,45,76)
Latissimus
dorsi
No Yes Yes Likely experiences greater hypertrophy at
longer muscle lengths.
(18)
Pectoralis
major
Yes Yes Yes Likely experiences greater hypertrophy at
longer muscle lengths. May also
experience active insufficiency.
(17)
Deltoid group Yes Yes Yes/No All 3 heads likely experience greater
hypertrophy at longer lengths but may
also experience active insufficiency.
Posterior deltoid is not active on
descending portion.
(17)
Trapezius Yes Yes No May not necessitate training at longer
lengths. May experience active
insufficiency at short lengths.
(17)
Biceps Yes Yes No May not necessitate training at longer
lengths. Likely experiences active
insufficiency at short lengths.
(14,30,49,55,69)
Triceps No Yes No Muscle length likely irrelevant for
maximizing triceps hypertrophy.
(19,44,68)
Muscle Hypertrophy Response
VOLUME 00 | NUMBER 00 | MONTH 202212
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
range of motion elbow flexion train-
ing was found to induce more muscle
damage in the biceps than partial
range of motion training. Muscle
damage and the resultant soreness
can negatively affect recovery and
future training session quality, but
the preliminary theory presented
here suggests that there is no hyper-
trophic benefit to using a full range of
motion when training the biceps. To
the strength and conditioning profes-
sional limited by time or scheduling
constraints, using these potential
findings may offer useful insight that
aids in program design.
Importantly, the practitioner may also
need to consider the inherent alter-
ations in muscle and joint moments
when modifying the range of motion
used in resistance training exercises.
It is generally accepted that for most
muscles, increasing the flexion angle
of a joint will result in a greater inter-
nal moment, and thus, larger levels of
tension experienced by the target
muscle. Indeed, preliminary research
would suggest that increasing the
range of motion (and resultant inter-
nal moment) enhances hypertrophic
adaptations in some muscles but not
others, which may embolden the
practical usefulness of the length-
tension curve in this aspect. Although
the concept of joint and muscle
moments likely interacts with the pre-
sented theories relative to the length-
tension curve, further research is war-
ranted to ascertain the independence
of each stimulus about hypertrophic
outcomes.
Relative to the other hard sciences,
exercise and strength training
research is a relatively new endeavor
(20). New findings and theories are
published virtually every day, often-
times with inconclusive results that
warrant further research. Unique
training methods and theories are
occasionally met with resistance
from practitioners, especially because
of the common use of untrained sub-
jects in strength training literature. It is
well-established that adaptations to
training differ greatly between trained
and untrained individuals (1,2) which
can reduce the applicability of a study’s
results. Furthermore, contradictory
findings, such as seen between Bloom-
quist et al. (5) and Pinto et al. (55), can
add to the general confusion of the field
when appropriate connections between
muscle properties and their influence on
adaptations are not made.
It is difficult to identify holes in the
research when it comes to strength
training ranges of motion, associated
muscle lengths, and long-term adapta-
tions because the topic itself is a hole
in the research and requires further
investigation. Future research should
endeavor to perform varying range of
motion training with all the major
muscle groups to assess the veracity
of the theory presented herein. In addi-
tion, using trained subjects in these
investigations offer more valid insights
for the practicing strength and condi-
tioning professional. Finally, investiga-
tions such as Stasinaki et al. (68) may
be considered a gold standard in this
realm in which ultrasonography was
used to measure muscle fascicle
length which validated the joint range
of motion used in the training proto-
col. Until the appropriate literature
has been established, the theory pre-
sented in this review may serve as
the proverbial bridge between science
and application for the strength and
conditioning practitioner and fitness
enthusiast alike.
Conflicts of Interest and Source of Funding:
The authors report no conflicts of interest
and no source of funding.
Charlie R.
Ottinger is the
Director of
Human Perfor-
mance at the
Applied Science
and Performance
Institute.
Matthew H.
Sharp is the Vice
President of
Research at the
Applied Science
and Performance
Institute.
Matthew W.
Stefan is a
Research Scien-
tist at the
Applied Science
and Performance
Institute.
Raad H. Gheith
is a Research
Scientist at the
Applied Science
and Performance
Institute.
Fernando de la
Espriella is the
Director of Crea-
tives at the
Applied Science
and Performance
Institute.
Jacob M.
Wilson is the
Chief Executive
Officer at the
Applied Science
and Performance
Institute.
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