2019_HighResistance-TrainingVolumeEnhancesMuscleThicknessinResistance-TrainedMen

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High Resistance-Training Volume Enhances Muscle Thickness in Resistance-
Trained Men
Article  in  The Journal of Strength and Conditioning Research · October 2019
DOI: 10.1519/JSC.0000000000003413
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RESPOSTAS AGUDAS DE INDICADORES DE FADIGA E INCHAÇO MUSCULAR APÓS TREINAMENTO DE FORÇA COM RESTRIÇÃO DE FLUXO COM O USO DE BANDAS ELÁSTICAS
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Felipe Brigatto
Universidade Metodista de Piracicaba (Unimep)
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Leonardo Emmanuel Medeiros Lima
Universidade Metodista de Piracicaba (Unimep)
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Moisés Germano
Universidade Metodista de Piracicaba (Unimep)
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Marcelo Saldanha Aoki
University of São Paulo
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Original Research
HighResistance-Training VolumeEnhancesMuscle
Thickness in Resistance-Trained Men
Felipe A. Brigatto,1,2 Leonardo Emmanuel de Medeiros Lima,1 Moisés D. Germano,1 Marcelo S. Aoki,3
Tiago V. Braz,1 and Charles R. Lopes1,4
1Methodist University of Piracicaba, Human Performance Research Laboratory, Piracicaba, São Paulo, Brazil; 2Anhanguera University
Center, Leme, São Paulo, Brazil; 3School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, Brazil; and 4Adventist
Faculty of Hortolândia, Hortolândia, São Paulo, Brazil
Abstract
Brigatto, FA, Lima, LEdM, Germano, MD, Aoki, MS, Braz, TV, and Lopes, CR. High resistance-training volume enhances muscle
thickness in resistance-trained men. J Strength Cond Res XX(X): 000–000, 2019—This study investigated the effects of different
volumes of resistance training (RT) (8 weeks of 16, 24, and 32weekly sets permuscle group) onmuscular strength and hypertrophy.
Subjects were pair-matched according to baseline strength and then randomly assigned to 1 of 3 experimental groups: 16 weekly
sets permuscle group (G16, n5 9), 24weekly sets permuscle group (G24, n5 9), or 32weekly sets permuscle group (G32, n5 9).
All other RT variables (e.g., exercise performed, exercise order, weekly frequency, range of repetitions, rest intervalbetween sets
and exercises, etc.) were maintained constant. The total load lifted was calculated for every RT session to compare the accu-
mulated external training load among experimental groups across the intervention period. Testing was conducted before in-
tervention (pre) and after 8-week (post-8) periods formaximal voluntarymuscle strength (1 repetitionmaximum [1RM] test for bench
press and parallel back squat exercises) and muscle thickness (MT) of the biceps brachii, triceps brachii, and vastus lateralis. The
major findings were as follows: (a) all RT volumes increased bench press and parallel back squat 1RM and (b) all RT volumes
increased the biceps brachii, triceps brachii, and vastus lateralis MT. The magnitude of increase in 1RM and MT of the lower body
when training with 32 weekly sets per muscle group was higher than for 16 weekly sets per muscle group. The magnitude of the
increase in MTTB was higher when training with 32 weekly sets than for 16 weekly sets.
Key Words: dose-response relationship, hypertrophy, muscle strength
Introduction
The primary goals of individuals engaged in resistance training
(RT) programs are to improve strength and muscle hypertrophy.
In this context, it is well accepted that these neuromuscular
adaptations are maximized by the appropriate manipulation of
RT variables, such as volume, intensity, frequency of training, rest
interval, selection and order of exercises, velocity of execution,
muscular actions, and range of motion (25).
Training volume, commonly defined as total load lifted (TLL:
sets3 repetitions3 external load), is considered to be one of the
most critical variables in this regard (8). Moreover, the total
number of sets to failure, or near to, seems to be an adequate
method to quantify training volume if all the other variables are
kept constant (2). In fact, systematic reviews with meta-analyses
have consistently shown a clear dose-response relationship be-
tween the total weekly number of sets per muscle group and
neuromuscular adaptations, muscle strength (15,24,27), and
muscle hypertrophy (16,29).
Regarding muscle strength, a recent meta-analysis showed that
a moderate (defined as 5–9 sets per exercise) to high ($10 sets per
exercise) weekly training volume is more effective for strength
gain as compared to lower training volume (#5 sets per exercise)
(24). It should be noted, however, that only 2 of the studies in-
cluded in the analysis used adequate experimental designs for the
investigation of a dose-response relationship among trained
individuals. The experimental designs involved at least 3 experi-
mental groups with different training volumes (17,20).
Similarly, a moderate (5–9 sets permuscle group) to high (101
sets per muscle group) weekly training volume is indicated to
induce muscle growth as compared to lower training volume (,5
sets per muscle group) (29). An added limitation to these findings
is that only 2 of the 15 studies that achieved inclusion criteria were
conducted in individuals with previous RT experience (20,26).
This observation is of relevance because there is compelling evi-
dence that resistance-trained individuals respond differently to
those who have not previously performed RT (22).
The findings of these recent meta-analyses were, however, re-
stricted to a maximum of 10 total weekly sets per muscle group.
As such, the analysis was only able to determine dose-response
effects up to this weekly training volume due to the paucity of the
research on higher RT volume programs. Thus, it remains unclear
as to whether RT, when performed with a higher volume, can
continue to enhance the hypertrophic response and, if so, at what
point these results reach the plateau. Furthermore, to the best of
the authors’ knowledge, only 2 published studies have in-
vestigated the effects of different RT volumes on morphological
adaptations using a dose-response study design among resistance-
trained individuals and using a training volume of greater than 10
sets per muscle group per week (20,30).
Given the existing gaps in the current literature and the
growing interest in this topic, the purpose of this study was to
investigate the chronic effects of training muscle groups with 16,
Address correspondence to Felipe A. Brigatto, filephi@gmail.com.
Journal of Strength and Conditioning Research 00(00)/1–9
ª 2019 National Strength and Conditioning Association
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mailto:filephi@gmail.com
24, and 32 sets per muscle group per week on neuromuscular
performance and morphological adaptations in resistance-
trained men. The authors used high RT volumes, typically asso-
ciated with bodybuilding training systems (9), and the use of
validated diagnostic imaging methods to directly assess changes
in muscle thickness (MT) (e.g., ultrasound). Based on previous
meta-analyses, the authors hypothesized that there would be
a graded outcome response, with an increasing gain in muscular
strength and hypertrophy seen for 16, 24, and 32 weekly sets per
muscle group programs, respectively.
Methods
Experimental Approach to the Problem
This study followed a randomized, longitudinal design (33).
Subjects were pair-matched according to baseline strength and
then randomly assigned to 1 of the 3 experimental groups: 16
weekly sets per muscle group (G16, n 5 9), 24 weekly sets per
muscle group (G24, n 5 9), or 32 weekly sets per muscle group
(G32, n 5 9). All other RT variables (e.g., exercise performed,
exercise order, weekly frequency, range of repetitions, rest in-
terval between sets and exercises, etc.) were maintained constant.
The experimental period lasted 11 weeks: 1st week—
familiarization period; 2nd week—preintervention period (base-
line); 3rd-10th week—training intervention period; and 11th
week—postintervention period. The training intervention period
lasted 8 weeks, and the TLL was calculated for every RT session
to compare the accumulated external training load among ex-
perimental groups, across the intervention period.
Testing was conducted before intervention (pre) and after the
8-week (post-8) period for maximal voluntary muscle strength
(1 repetition maximum [1RM] test for bench press and parallel
back squat exercises) and MT of the biceps brachii, triceps bra-
chii, and vastus lateralis. In the first week, volunteers attended
2 familiarization sessions in the laboratory. The subjects refrained
from all physical exercises other than activities of daily living for
at least 48 hours before the first familiarization session. In the first
session, volunteers were familiarized with the 1RM test. The
following day (24 hours after), volunteers were familiarized with
standard procedures adopted in all RT exercises, such as body
position, cadence, range of motion, rest, etc. In addition, subjects
were trained and instructed to record their dietary intake.
Subjects
Twenty-seven healthymen (27.26 7.1 years [range 19–31 years];
height 5 176 6 6.1 cm; total body mass 5 80.6 6 6.5 kg; RT
experience 5 40.2 6 13.2 months [mean 6 SD; range 24–120
months]; RT frequency5 4.96 0.9 session perweek) volunteered
to participate in this study. The sample size was justified by
a priori power analysis based on a pilot study, where the vastus
lateralis MT was assessed as the outcome measure with a target
effect size (ES) difference of 0.75, an alpha level of 0.05, and
a power (12b) of 0.80 (7). All subjects were resistance-trained;
performing RT on a minimum of 3 days per week for at least 1
year at the university’s RT gym. All subjects regularly performed
(minimum frequency of once a week) all exercises used in the
training intervention and in the strength tests for at least 1 year
before entering the study. The number of sets per muscle group
that the subjects usually performed before the study is outlined in
Table 1. Moreover, subjects were free from any existing muscu-
loskeletal disorders; history of injury with residualsymptoms
(pain, “giving-away” sensations) in the trunk, upper limbs, and
lower limbs within the last year and stated that they had not taken
anabolic steroids or any other illegal agents known to increase
muscle size at the time or during the previous year. Thus, par-
ticipation in the study required that the subjects answered nega-
tively to all questions on the Physical Activity Readiness
Questionnaire and had a minimum 1RM parallel back squat of
1.253 total bodymass and a 1RMbench press of at least equal to
total body mass (13). All subjects read and signed an informed
consent document approved by the Methodist University of
Piracicaba research ethics committee (protocol 1.749.141).
Procedures
Resistance-Training Program. The RT protocol consisted of 9
exercises targeting each of themajormuscle groups. Subjects were
instructed to refrain from any additional resistance-type training
for the duration of the study. The specific protocols for experi-
mental groups are outlined in Table 2. The exercises were chosen
based on their common inclusion in bodybuilding and strength-
type RT programs (18). The weekly training protocol for all
groups consisted of 2 split routines targeting specific muscle
groups: split routine A (Arout) and split routine B (Brout).
The weekly training for all groups consisted of 4 training sessions
(Arout1Brout1Arout1Brout). Thus, G16, G24, andG32 performed
16, 24, and 32weekly sets for themajormuscle groups, respectively,
comprising 8, 12, and 16 sets of multijoint exercises and 8, 12, and
16 sets of single-joint exercises, respectively, except for the hamstring
muscles, which were stimulated with 16, 24, and 32 weekly sets of
single-joint exercise (machine-seated leg curl). Each set involved
8–10 maximum repetitions (RM) with 60 seconds of rest afforded
between sets and 120-second rest between exercises. All sets were
conducted to the point of momentary concentric muscular failure,
operationally defined as the inability to perform another concentric
repetition while maintaining adequate form. The external load (kg)
was adjusted for each exercise, as needed, on successive sets to ensure
that subjects achieved failure in the target repetition range. The ca-
dence of repetitions was conducted in a controlled fashion, with
concentric and eccentric actions of approximately 1.5 seconds, for
total repetitiondurationof approximately 3 seconds.AllRT sessions
were preceded by a specific warm-up consisting of 2 sets of 10
repetitionswith 50%of the load used in the first set of all exercises of
the session. All subjects reported a rating of perception exertion
(RPE) based on the RPE/repetitions in reserve scale (11) of 9.5–10
for all sets and exercises in RT sessions.
All routines were directly supervised by the research assistants
to ensure the correct performance of the respective routines. Be-
fore the training intervention period, all subjects underwent
10RM testing (according to guidelines established by the Na-
tional Strength and Conditioning Association, NSCA (18)) to
determine individual initial training loads for each exercise.
Attempts were made to progressively increase the load lifted each
week while maintaining the target repetition range. No injuries
were reported, and the adherence to the program was 100% for
all groups.
Estimate of Food Intake. To avoid potential dietary confounding
of results, subjects were advised to maintain their customary
nutritional regimen and to avoid taking any supplements during
the study period. Dietary nutrient intake was assessed by a 24-
hour food diary on 2 nonconsecutive weekdays and 1 day of the
weekend. The subjects were instructed to record in detail the time
Resistance-Training Volume (2019) 00:00
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of consumption and types and quantity of food preparations
consumed during 24 hours. The quantity of food was recorded in
cooking units (spoons, cups, and glasses) and transformed into
grams. The estimation of energy intake (macronutrients) was
analyzed by NutWin software (UNIFESP, Sao Paulo, Brazil). The
estimated food intakewas assessed duringweeks 1, 4, and 8 of the
training intervention period.
Criterion Measurements: Muscle Strength. Upper- and lower-
body maximum strength was assessed by 1RM testing in the
bench press (1RMBENCH) and parallel back squat (1RMSQUAT)
exercises. Subjects refrained from any exercise other than activi-
ties of daily living for at least 48 hours before baseline testing and
at least 48 hours before testing at the conclusion of the study.
Maximum strength testing was consistent with recognized
guidelines as established by the NSCA (18). Before testing,
subjects performed a general warm-up consisting of 5 minutes of
cycling (Schwinne; AC Sport, Vancouver, WA) at 60–70 rpm and
50 W. Subsequently, a specific warm-up set of the given exercise
of 5 repetitions was performed at ;50% 1RM followed by 1–2
sets of 2–3 repetitions at a load corresponding to ;60–80%
1RM. Subjects then performed sets of 1 repetition of increasing
weight for 1RM determination. The external load was adjusted
by ;5–10% in subsequent attempts until the subject was unable
to complete 1 maximal muscle action. The 1RM was considered
the highest load lifted. A 3- to 5-minute rest was used between
each successive attempt. All 1RM determinations were made
within 5 attempts.
Successful 1RMBENCH was achieved if the subject displayed
a 5-point body contact position (head, upper back, and buttocks
firmly on the bench with both feet flat on the floor), lowered the
bar to touch his chest, and executed full elbow extension. The grip
Table 1
Baseline descriptive statistics (mean 6 SD).*
Variables G16 (n 5 9) G24 (n 5 9) G32 (n 5 9) ANOVA 3 3 1 (p)
Age (y) 27.9 6 8.2 26.4 6 6.3 27.1 6 6.6 0.422
Total body mass (kg) 81.6 6 6.9 80.2 6 5.6 80.0 6 7.5 0.869
Height (cm) 179 6 6 176 6 7 174 6 6 0.325
RT experience (mo) 51 6 40 32 6 7 34 6 8 0.217
RT frequency (sessions·wk21) 4.8 6 0.9 5.2 6 1.1 4.9 6 0.8 0.396
Total no. of sets (sets·wk21) 226 6 128 171 6 47 210 6 50 0.368
No. of sets—chest (sets wk21) 27 6 14 20 6 7 25 6 7 0.294
No. of sets—back (sets wk21) 28 6 14 20 6 6 25 6 5 0.202
No. of sets— shoulder (sets·wk21) 45 6 27 34 6 11 43 6 14 0.421
No. of sets—biceps (sets wk21) 42 6 27 35 6 10 41 6 11 0.665
No. of sets–triceps (sets·wk21) 42 6 27 34 6 11 38 6 9 0.638
No. of sets–quadriceps (sets wk21) 21 6 13 16 6 5 19 6 7 0.642
No. of sets–hamstrings (sets·wk21) 21 6 13 12 6 8 18 6 7 0.137
1RMBENCH (kg) 93 6 20 103 6 23 98 6 20 0.122
1RMSQUAT (kg) 105 6 20 117 6 32 121 6 27 0.098
MT of the biceps brachii muscle (mm) 38.2 6 3.9 38.2 6 4.5 35.6 6 3.1 0.288
MT of the triceps brachii muscle (mm) 33.9 6 4.3 33.6 6 4.3 35.9 6 3.8 0.305
*G165 16 weekly sets per muscle group; G245 24 weekly sets per muscle group; G325 32 weekly sets per muscle group; ANOVA5 analysis of variance; RT5 resistance training; sets·wk215 sets per
week; 1RM 5 1 maximal repetition; MT 5 muscle thickness.
Table 2
Training protocols for experimental groups.*
Monday Tuesday Wednesday Thursday Friday
Arout Brout Arout Brout
G16 (n 5 9)
Bench press 4 3 8-10RM Lat pull-down 4 3 8-10RM REST Bench press 4 3 8-10RM Lat pull-down 4 3 8-10RM
Dumbbell flat fly 4 3 8-10RM Dumbbell reverse fly 4 3 8-10RM Dumbbell flat fly 4 3 8-10RM Dumbbell reverse fly 4 3 8-10RM
Cable triceps 4 3 8-10RM Biceps curl 4 3 8-10RM Cable triceps 4 3 8-10RM Biceps curl 4 3 8-10RM
Parallel back squat 4 3 8-10RM Seated leg curl 8 3 8-10RM Parallel back squat 4 3 8-10RM Seated leg curl 8 3 8-10RM
Leg extension 4 3 8-10RM Leg extension 4 3 8-10RM
G24 (n 5 9)
Bench press 6 3 8-10RM Lat pull-down 6 3 8-10RM REST Bench press 6 3 8-10RM Lat pull-down 6 3 8-10RM
Dumbbell flat fly 6 3 8-10RM Dumbbell reverse fly 6 3 8-10RM Dumbbell flat fly 6 3 8-10RM Dumbbell reverse fly 6 3 8-10RM
Cable triceps 6 3 8-10RM Biceps curl 6 3 8-10RM Cable triceps 6 3 8-10RM Biceps curl6 3 8-10RM
Parallel back squat 6 3 8-10RM Seated leg curl 12 3 8-10RM Parallel back squat 6 3 8-10RM Seated leg curl 12 3 8-10RM
Leg extension 6 3 8-10RM Leg extension 6 3 8-10RM
G32 (n 5 9)
Bench press 8 3 8-10RM Lat pull-down 8 3 8-10RM REST Bench press 8 3 8-10RM Lat pull1down 8 3 8-10RM
Dumbbell flat fly 8 3 8-10RM Dumbbell reverse fly 8 3 8-10RM Dumbbell flat fly 8 3 8-10RM Dumbbell reverse fly 8 3 8-10RM
Cable triceps 8 3 8-10RM Biceps curl 8 3 8-10RM Cable triceps 8 3 8-10RM Biceps curl 8 3 8-10RM
Parallel back squat 8 3 8-10RM Seated leg curl 16 3 8-10RM Parallel back squat 8 3 8-10RM Seated leg curl 16 3 8-10RM
Leg extension 8 3 8-10RM Leg extension 8 3 8-10RM
*G16 5 16 weekly sets per muscle group; G24 5 24 weekly sets per muscle group; G32 5 32 weekly sets per muscle group; Arout 5 split routine A; Brout 5 split routine B; RM 5 repetition maximum.
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width was standardized at 200% of biacromial width (21). In the
1RMSQUAT, subjects were required to squat down so that the top
of the thighwas parallel to the ground (;90° of knee joint flexion)
for the attempt to be considered successful, as determined by
a research assistant who was positioned laterally to the subject.
The barbell was positioned on the shoulders (high-bar position),
and the subjects’ feet were always positioned at hip width (5).
A 1RMBENCH testing was conducted before 1RMSQUAT with
a 20-minute rest period separating tests. Strength testing was
conducted using free weights. Recording of feet and hand place-
ment was made during familiarization strength testing and then
used for preintervention and postintervention performance tests
as well as at all training sessions. All testing sessions were su-
pervised by the research team to achieve a consensus for success
on each attempt. The test-retest intraclass correlation coefficient
(ICC), coefficient of variation (CV), and the typical error of the
measurement (TEM) calculated through the data collected during
the familiarization period and the preintervention period (5 days
between the test-retest) for 1RMBENCH were 0.989, 0.8%, and
2.05 kg, respectively. The ICC, CV, and SEM for 1RMSQUAT
were 0.990, 0.7%, and 1.95 kg, respectively.
Muscle Thickness. Ultrasound imaging was used to obtain the
assessment of MT. A trained technician performed all testing
using an A-mode ultrasound imaging unit (Bodymetrix Pro Sys-
tem; Intelametrix, Inc., Livermore, CA). After a generous appli-
cation of a water-soluble transmission gel (Mercur S.A.—Body
Care, Santa Cruz do Sul, Brazil) to the site to be evaluated, a 2.5-
MHz linear probe was placed perpendicular to the tissue interface
without depressing the skin. Equipment settings were optimized
for image quality, according to the manufacturer’s user manual
and held constant among testing sessions.When the quality of the
image was deemed to be satisfactory, the image was saved to the
hard drive, and MT dimensions were obtained by measuring the
distance from the subcutaneous adipose tissue–muscle interface
to themuscle-bone interface, as permethods used byAbe et al. (1).
Measurements were taken on the right side of the body at 3 sites:
biceps brachii (MTBB), triceps brachii (MTTB), and vastus lateralis
(MTVL). The upper-arm measurements were conducted while
subjects were standing, and the measurements of the thigh muscle
involved subjects lying supine on an examination table. For the
anterior and posterior upper arm,measurements were taken 60%
distal between the lateral epicondyle of the humerus and the
acromion process of the scapula; for the thigh muscle, measure-
ments were taken at 50% of the distance between the lateral
condyle of the femur and greater trochanter. For each measure-
ment, the examined limb was secured to minimize unwanted
movement. Tomaintain consistency between preintervention and
postintervention testing, each site was marked with henna ink
(reinforced everyweek). In an effort to help ensure that swelling in
the muscles from training did not obscure results, images were
obtained 48–72 hours before commencement of the study and
after the final training session. This is consistent with research
showing that an acute increase in MT returns to baseline within
48 hours after a RT session (19).
To further ensure accuracy of measurements, at least 3
images were obtained for each site. If measurements were
within 1 mm of one another, the figures were averaged to ob-
tain a final value. If measurements presented more than 1 mm
difference from one another, a fourth image was obtained, and
the closest 3 measurements were then averaged. The test-retest
ICC forMTBB, MTTB, andMTVL was 0.996, 0.998, and 0.999,
respectively. The CV for these measurements was 0.4, 0.6, and
0.6, respectively. The TEM for these measurements was 0.29,
0.42, and 0.41, respectively.
Total Load Lifted. Total load lifted (sets3 repetitions3 external
load [kgf]) (31) was calculated from training logs filled out by
research assistants for every RT session. The accumulated TLL
(ATLL) was the sum of all RT weeks. Only repetitions performed
through a full range of motion were included for analysis. The
data were expressed in kilogram-force units (kgf). The DTLL
described the difference in the TLL between weeks 8 and 1 (e.g.,
TLL in the week 8 minus the TLL in the week 1).
Statistical Analyses
The normality and homogeneity of the variances were verified
using the Shapiro-Wilk and Levene tests, respectively. Before
analysis, all data were log-transformed for analysis to reduce bias
arising from nonuniformity error (heteroscedasticity). The mean,
SD, and 95% confidence intervals (CIs) were used after data
normalitywas assumed. A repeated-measures analysis of variance
(ANOVA) was used to compare 1RMBENCH, 1RMSQUAT, MTBB,
MTTB, andMTVL time effect (before vs. after week 8)3 3 groups
(G16 vs. G24 vs. G32). A 33 3 ANOVA (interaction groups and
time [week 1, 4, and 8]) was used to compare the food-intake
variables. A 1 3 3 ANOVA (G16 vs. G24 vs. G32) was used to
compare the variables ATLL and ΔTLL (week 8—week 1). Post
hoc comparisons were performed with the Bonferroni correction.
Assumptions of sphericity were evaluated using theMauchly test.
Where sphericity was violated (p , 0.05), the Greenhouse-
Geisser correction factor was applied. In addition, ESs were
evaluated using a partial eta squared (h2
p), with,0.06, 0.06–0.14,
and .0.14 indicating a small, medium, and large effect, re-
spectively. The ES in absolute difference (before vs. after 8 weeks)
was calculated in raw values of the variables using the stan-
dardized difference, based on Cohen’s d units by means (d value)
(6). The d result was qualitatively interpreted using the following
thresholds: ,0.2, trivial; 0.2–0.6, small; 0.6–1.2, moderate;
1.2–2.0, large; 2.0–4.0, very large; and .4.0, extremely large. If
the 90% confidence limits overlapped, small positive and nega-
tive values for the magnitude were deemed unclear; otherwise,
this magnitude was deemed to be the observed magnitude (11).
Smallest worthwhile change (SWC) in MTBB, MTTB, and MTVL
was calculated by the formula SWC 5 TEM 3 90% CIs (4).
Hence, the TEM is multiplied by 1.746 to establish the 90% CI,
according to the distribution of probability for t (16) as p, 0.10
i.e., degrees of freedom (DF—16). The TEM for these measure-
ments was 0.42 mm (MTTB), 0.29 (MTBB), and 0.41 mm (MTVL)
(3). Smallest worthwhile change was used as a trivial area (gray
bar) of the smallest true individual change of subjects (12). The
relationship between variables was determined through Pearson
correlation. The 95%CI of the association between variables was
calculated. The following criteria were adopted to interpret the
magnitude of the correlation (r): #0.1, trivial; .0.1–0.3, small;
.0.3–0.5, moderate; .0.5–0.7, large; .0.7–0.9, very large; and
.0.9–1.0, almostperfect (12). If the 95% confidence limits
overlapped, small positive and negative values for the magnitude
were deemed unclear; otherwise, this magnitude was deemed to
be the observed magnitude (12). All analyses were performed
using SPSS-22.0 software (IBM Corp., Armonk, NY). The
adopted significance was p # 0.05. Figures were assembled in
GraphPad Prism version 6.0 software (La Jolla, CA) following the
assumptions for continuous data.
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Results
No significant difference was noted between groups for any of the
baseline measurements (all p . 0.05 [Table 1]). There was no
significant difference in any dietary intake variables (kcal, pro-
teins (g), carbohydrate (g), and lipids (g)) either within or between
groups over the course of the study (all p . 0.05 [Table 3]).
Maximal Strength
A significant main effect of time (F1,8 5 640.565, p 5 0.001, h2
p 5
0.988), but not group3 time interaction (F1,8 5 1.371, p5 0.275,
h2
p 5 0.146), was observed for the 1RMBENCH. There was a signif-
icantmain effect of time (F1,85 17.761, p5 0.003,h2
p 5 0.689) and
group3 time interaction (F1,85 15.012,p5 0.038,h2
p 5 0.614) for
1RMSQUAT (after 8 weeks G16 vs. G32 p5 0.023) (Table 4). Effect
size in absolute difference (after 8 weeks–before) was moderate be-
tween G16 vs. G24 (d 5 0.63, 90% confidence limits [CL] 5
0.07–1.19; d 5 1.14, 90% CL 5 0.68–1.60), trivial and moderate
between G16 vs. G32 (d 5 0.07, 90% CL 5 20.35 to 0.49; d 5
0.78, 90%CL50.37–1.19), andmoderate betweenG24 vs.G32 (d
5 0.82, 90%CL5 0.40–1.24; d5 0.85, 90%CL5 0.34–1.36) for
the 1RMBENCH and 1RMSQUAT, respectively (Figure 1).
Muscle Thickness
A significantmain effect of time (F1,85 154.217, p5 0.0001,h2
p 5
0.951) but not group3 time interaction (F1,8 5 2.076, p5 0.188,
h2
p 5 0.206), was observed forMTBB. There was a significantmain
effect of time (F2,165 137.451, p5 0.001, h2
p 5 0.945) and group
3 time interaction (F1.435,11.4775 21.268, p5 0.001, h2
p 5 0.727)
for MTTB (after 8 weeks G16 vs. G32, p 5 0.003) (Table 5). A
significant main effect of time (F2.16 5 161.933, p 5 0.001, h2
p 5
0.953) and group 3 time interaction (F4,32 5 37.509, p 5 0.001,
h2
p 5 0.824) was observed forMTVL (after 8 weeksG16 vs. G32, p
5 ,0.01) (Table 5). Effect size in absolute difference (after 8
weeks–before) was large between G16 vs. G24 (d 5 1.50, 90%
CL5 0.91–1.99; d5 1.92, 90%CL5 1.04–2.80; d5 1.79, 90%
CL 5 1.19–2.29), very large and extremely large between G16
vs. G32 (d 5 3.77, 90% CL 5 2.70–4.84; d 5 5.11, 90% CL 5
4.34–5.89; d 5 4.81, 90% CL 5 4.09–5.53), and large and very
large between G24 vs. G32 (d5 2.07, 90% CL5 1.14–3.00; d5
1.71, 90% CL5 0.83–2.59; d5 2.37, 90% CL5 1.35–3.39) for
MTBB, MTTB, and MTVL, respectively (Figure 1).
Figure 2 shows individual comparisons between subjects for
absolute MT difference from before to week 8. G32 presented
a higher number of subjects who benefited in the MTBB, MTTB,
and theMTVLwhen comparedwith G24 andG16. The difference
variation was G16 (MTBB 5 range 0–0.4 mm, MTTB 5 range
0–0.4 mm, MTVL 5 range 0–1.7 mm), G24 (MTBB 5 range
0–1 mm, MTTB 5 range 0.4–3.1 mm, MTVL 5 range 1–3 mm),
and G32 (MTBB 5 range 0.6–1.7 mm, MTTB 5 range
1.8–3.5 mm, MTVL 5 range 2.5–4.2 mm).
Total Load Lifted
A significant main effect of groups was observed for TLL
(F2.253,18.021 5 25.622, p5 0.001, h2
p 5 0.675) and DTLL (F7,56
5 3.123, p 5 0.115, h2
p 5 0.281). G32 demonstrated a greater
TLL when compared with G24 (38.0%; d 5 2.90, 90% CL 5
21.90 to 3.90) andG16 (57.1%; d5 6.05, 90%CL5 4.45–7.65)
(Figure 3A). G32 showed an increase in TLL at week 8 vs. week 1
(ΔTLL) compared with G24 (d5 1.98, 90%CL5 1.05–2.91) and
G16 (d 5 6.05, 90% CL 5 4.43–7.67) (Figure 3B).
Correlations Between Training Load and
Dependent Variables
Figure 3 illustrates the correlations between accumulated TLL
(ATLL) and absolute differences (raw value—Dkg andDmm) from
pre– to post–8 weeks in dependent variables for all subjects pooled
together. Accumulated TLL was showed a slight correlation with
Dkg 1RMBENCH (r 5 0.28, 95% CI 5 20.10 to 0.60) and was
moderately correlated with Dkg 1RMSQUAT (r 5 0.49, 95% CI 5
0.25–0.73). However, ATLL correlated highly with DmmMTBB (r
5 0.84, 95% CI5 0.75–0.93), DmmMTTB (r5 0.86, 95% CI5
0.79–0.94), and Dmm MTVL (r 5 0.88, 95% CI 5 0.82–0.95).
Table 3
Estimated dietary nutrient intake for G16, G24, and G32 (mean 6 SD).*
Variables Week 1 Week 4 Week 8
ANOVA 3 3 2
Time Time 3 group
p p
Total (kcal)
G16 3,158 6 262 3,136 6 279 3,137 6 316 0.301 0.092
G24 3,110 6 190 3,052 6 258 3,124 6 273
G32 3,103 6 330 3,065 6 283 3,089 6 279
Protein (g)
G16 144 6 15 144 6 16 144 6 15 0.445 0.388
G24 137 6 13 136 6 12 138 6 13
G32 140 6 12 140 6 14 136 6 15
Carbohydrate (g)
G16 490 6 46 480 6 33 484 6 47 0.161 0.092
G24 470 6 40 464 6 40 473 6 39
G32 478 6 46 470 6 39 480 6 41
Lipids (g)
G16 69 6 9 71 6 10 69 6 10 0.358 0.114
G24 66 6 9 63 6 8 66 6 8
G32 70 6 13 70 6 11 69 6 9
*G165 16 weekly sets per muscle group; G245 24 weekly sets per muscle group; G325 32 weekly sets per muscle group; ANOVA5 analysis of variance; Total (kcal)5 total kilocalories intake; g5 grams.
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Discussion
This study investigated the effects of different volumes (16, 24,
and 32 weekly sets per muscle group) on muscular strength and
hypertrophy after 8 weeks of RT. The main findings were as
follows: (a) all RT volumes increased bench press and parallel
back squat 1RM and (b) all RT volumes increased the biceps
brachii, triceps brachii, and vastus lateralis MT. The magnitude
of increase in 1RMandMTof the lower body,when trainingwith
32 weekly sets per muscle group, was higher than for 16 weekly
sets per muscle group. Likewise, the magnitude of increase in
MTTB, when training with 32 weekly sets, was higher than for 16
weekly sets (Figure 4).
Regarding muscle strength, when compared with previous
studies investigating the effects of varying RT volumes on neu-
romuscular adaptations conducted in resistance-trained sub-
jects, the current findings corroborate those of Marshall et al.
(17) and are slightly in contrast with the data from Heaselgrave
et al. (10), Ostrowski et al. (20), and Schoenfeld et al. (30).
Marshall et al. (17) (2 vs. 8 vs. 16 weekly sets of back squat
exercise) observed that the 16-set group was significantly
stronger in the 1RM squat test than the 2-set group after 3 weeks
of training and remained stronger after 6 and 10 weeks of
training. Heaselgrave et al. (10) (9 vs. 18 vs. 27 weekly sets of
biceps RT), Ostrowski et al. (20) (3 vs. 6 vs. 12 weekly sets per
muscle group), and Schoenfeld et al. (30) (6 vs. 18 vs. 30 and 9
vs. 27 vs. 45 sets per muscle group for upper and lower limbs,
respectively) showed no difference in between groups for iso-
metric and 1RM maximum strength tests.
Interestingly, in this study, themagnitude of increase for training
with 32 weekly sets was higher than for 16 weekly sets for
1RMSQUAT but not for 1RMBENCH. The RT volume that was
commonly performed by the subjects before the study could par-
tially explain these findings (Table 1). Although no among-group
differences were observed for the total number of weekly sets
performed for the quadriceps muscles before the study, impor-
tantly, the number of weekly sets for this muscle was reduced in the
G16 groupduring the intervention (from21 to 16 sets),whereas for
G24 and G32, the number of weekly sets for the quadriceps was
increased (from 16 to 24 and 19 to 32, respectively). Although
a similar occurrence was observed for the pectoralis major muscle
(decreased RT volume for G16 and increased RT volume for G24
and G32, when comparing the RT volume commonly used by the
subjectsbefore the study), it should be noted that different muscles
may have different dose-response curves for RT volume. This
seems to be the case for the upper- vs. lower-bodymuscles (28,34).
Some experimental evidence demonstrated that lower-body mus-
cles somehow benefit more from a higher RT volume compared
with upper-limb muscles (28). To verify the weekly volume per
muscle group performed by resistance-trained subjects, Teixeira
et al. (32) analyzed the current training programs of 63 resistance-
trained men. The results showed a difference between muscles in
which the weekly volume for the pectoralis major was significantly
higher than the volume used for the quadriceps (median with
Table 4
Before and after 8 weeks of muscle strength measures (mean 6 SD).*
Variables Before After 8 weeks Δ% MD (95% CI)
Time Time 3 group
p p
1RMBENCH (kg)
G16 93 6 20 115 6 21† 23.6 22.1 (14.2–29.9) 0.001 0.275
G24 103 6 23 124 6 23† 20.9 21.5 (16.8–26.2) 0.001
G32 98 6 20 126 6 17† 28.7 28.2 (21.1–35.3) 0.001
1RMSQUAT (kg)
G16 105 6 20 123 6 19† 16.6 17.5 (13.8–21.2) 0.001 0.038
G24 117 6 32 138 6 32† 18.1 21.2 (17.6–24.7) 0.001
G32 121 6 27 151 6 25†‡ 25.4 30.7 (18.6–42.8) 0.001
*G165 16 weekly sets per muscle group; G245 24 weekly sets per muscle group; G325 32 weekly sets per muscle group; 1RMBENCH5 1 maximal repetition test in bench press exercise; 1RMSQUAT5 1
maximal repetition test in parallel back squat exercise; MD 5 mean difference; 95% CI 5 95% confidence interval.
†Significantly greater than the corresponding preintervention value (p , 0.05).
‡Significantly greater than the G16 post–8-week value (p , 0.05).
Figure 1. Efficiency of the group that trained 32 weekly sets per muscle group (G32) in
comparison with the groups that trained 24 and 16 weekly sets per muscle group (G24 and
G16) to improve muscle thickness of the triceps brachii (MTTB), biceps brachii (MTBB), and
vastus lateralis (MTVL) muscles. The Cohen’s of effect size (ES) principle 6 90% confidence
intervals were used to compare the absolute differences of the variables before vs. after 8
weeks. Trivial areas were the smallest worthwhile change (SWC) (see Methods). *Large ES;
**very large ES; ***extremely large ES.
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interquartile ranges [IQR]: 30 [IQR 5 8] vs. 16 [IQR 5 12], re-
spectively). These data demonstrate that resistance-trained men
commonly use a higher weekly volume for the upper body com-
paredwith the lower-body. Thus, it is plausible to hypothesize that,
for men, the muscles of upper limbs are already better adapted to
higher weekly volumes, whereas lower limbs would be more sus-
ceptible to increases in training volume.
Therefore, it is feasible that the subjects in theG32unduly benefited
from the unfamiliar stimulus of training with a higher RT volume for
the lower-bodymuscles, where the strength gain was influencedmore
by this new stimulus, in comparison with the upper-body muscles.
Regarding muscle hypertrophy, the present findings essentially
reflected recent meta-analytic data showing a dose-response re-
lationship between RT volume and hypertrophy (29). This study
indicates that a substantially greater training volume may be bene-
ficial to enhance muscle growth in subjects with previous RT ex-
perience, at least over an 8-week training period. Hypertrophy for 2
of the 3measuredmuscleswas significantly greater for the highest vs.
lowest RT volume condition. Only the biceps brachii muscle did not
show a statistically greater increase in MT between conditions.
Moreover, a dose-response relationship was detected for the mag-
nitude of ES for MT, in the higher RT volumes conditions, where
G32 . G24 . G16 for all measured muscles (Figure 1).
Another interesting aspect of the present findings is that al-
though a significant within-group difference was observed in the
G16 for all muscles measured, and the absolute differences from
pre– to post–8 weeks forMTBB (0.26 0.1 mm) andMTTB (0.36
0.2mm)were below TEM for these measurements (0.29 and 0.42
for MTBB andMTTB, respectively). In fact, all subjects in the G16
presented absolute changes below the SWC (MTBB 5 range
0–0.4mm, SWC5 0.50mm;MTTB5 range 0–0.4mm, and SWC
5 0.73). Therefore, it is possible that the changes observed for
these outcomes in the G16 were not due to the RT intervention
but the expected variation of these measurements.
Several potential relationships between RT volume and skeletal
muscle hypertrophy/strength have been postulated: (a) a dose-
response relationship, where gradual increases in weekly RT vol-
ume lead to a greater increase inmuscle mass and strength (24,29),
(b) an inverted-U relationship, whereby increasing weekly RT
volume beyond a certain threshold negatively impacts skeletal
muscle accretion (8), and (c) no relationship between weekly RT
volume and muscle hypertrophy or strength (10,20,30).
To date, the literature has failed to identify the optimal RT
volume per muscle group to maximize muscle hypertrophy and
strength. Furthermore, the existing literature has focused on
muscular adaptations to relatively low-volume RT (#10–12
weekly sets), highlighting a clear need to investigate this re-
lationship by implementing higher weekly RT volumes (.10–12
weekly sets) (29).
Taken together with the findings of Schoenfeld et al. (30), the
present results imply that for improvement in hypertrophy in
resistance-trained subjects, a higher RT volume (32 weekly sets
per muscle group in this study and 30–45 weekly sets per muscle
group in the study of Schoenfeld et al. (30)) is crucial for en-
hancing muscle hypertrophy. Therefore, future studies should
investigate the following: (a) when the RT volume threshold for
resistance-trained subjects is reached and (b) at which point the
RT volume becomes detrimental for hypertrophy gain, thus ex-
perimentally demonstrating the hypothetical inverted-U curve for
the dose-response relationship between RT volume and muscle
hypertrophy. Moreover, the current data demonstrated that
ATLL was highly correlated with Dmm (r 5 0.84–0.88).
Other criticism of high RT volume protocols is that this ap-
proach is prone to overtraining and can be detrimental (8).
Contrary to this hypothesis, the current results demonstrated that
Table 5
Before and after 8 weeks of muscle morphology measures (mean 6 SD).*
Variables Before After 8 weeks Δ% MD (95%CI)
Time Time 3 group
p p
MTBB (mm)
G16 38.2 6 3.9 38.4 6 3.9† 0.5 0.2 (0.1–0.3) 0.01
G24 38.2 6 4.5 38.7 6 4.6† 1.3 0.5 (0.2–0.8) 0.001 0.206
G32 35.6 6 3.1 36.7 6 3.0† 3.1 1.1 (0.8–1.4) 0.001
MTTB (mm)
G16 33.9 6 4.3 34.2 6 4.3† 0.8 0.2 (0.1–0.4) 0.022
G24 33.6 6 4.3 35.0 6 4.7† 4.0 1.3 (0.5–2.1) 0.001 0.001
G32 35.9 6 3.8 38.4 6 4.2†‡ 7.0 2.5 (1.9–3.1) 0.001
MTVL (mm)
G16 36.2 6 4.4 36.9 6 4.0† 2.1 0.7 (0.1–1.3) 0.001
G24 35.4 6 5.0 37.4 6 4.6† 5.6 1.9 (1.2–2.7) 0.001 0.001
G32 37.1 6 5.1 40.6 6 5.1†‡ 9.4 3.4 (2.9–3.9) 0.001
*G165 16 weekly sets per muscle group; G245 24 weekly sets per muscle group; G325 32 weekly sets per muscle group; MTBB5muscle thickness of the biceps brachii muscle; MTTB5muscle thickness
of the triceps brachii muscle; MTVL 5 muscle thickness of the vastus lateralis muscle; MD 5 mean difference; 95% CI 5 95% confidence interval.
†Significantly greater than the corresponding preintervention value (p , 0.05).
‡Significantly greater than the G16 post–8-week value (p , 0.05).
Figure 2. Univariate scatterplot with means of absolute dif-
ference from before to week 8 in muscle thickness (MT) of the
biceps brachii (MTBB), triceps brachii (MTTB), and the vastus
lateralis (MTVL) of the 3 groups (G16, G24, and G32). Trivial
areas were the smallest worthwhile change (SWC) (see
Methods).
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www.nsca.comthe higher RT volume implemented was not associated with
detrimental effects. By contrast, the DTLL was superior for the
higher RT volume conditions, where G32.G24.G16. That is,
the capacity to accumulate more TLL over the weeks was not
negatively influenced by the higher RT volume conditions. In fact,
higher number of weekly sets apparently resulted in a greater
capacity to increase the TLL over the weeks. Although this study
has consistently demonstrated that a higher RT volume is well
tolerated with no detrimental effects, it is plausible that this
greater TLL, when achieved through high RT volume protocols
(G24 and G32), may culminate in detrimental effects if executed
for a longer time frame (more than 8 weeks). However, Radaelli
et al. (23) reported a greater increase in elbow flexor MT with 30
weekly sets per muscle group vs. 6 or 18 sets for 6 months, in
untrained individuals. This previous study demonstrated that
higher volumes are well tolerated even when executed for longer
periods and even when performed by untrained subjects. It is,
therefore, evident that further investigation in trained individuals
for longer time periods is warranted to better elucidate this topic.
This study has several limitations that must be considered when
attempting to draw evidence-based inferences. First, the study period
lasted only 8 weeks. Although this duration was sufficient to achieve
a significant increase in muscular strength and hypertrophy (assessed
by MT) in all groups, it is conceivable that results between groups
would have diverged over a longer time frame. Second, the novelty
factor of changing programs may have unduly influenced results.
Although, no between-groups differences were observed in the total
number of weekly sets performed for quadricep muscles before the
study, it is important to note that for G16, the number of weekly sets
for this muscle was reduced during the intervention (from 21 to 16
sets), whereas for G24 and G32, the number of weekly sets for the
quadriceps was increased (16–24 and 19–32, respectively). Although
this topic has not been well studied, there is evidence indicating that
muscular adaptations are enhanced when program variables are
altered outside of traditional norms (14). Therefore, it is feasible that
the subjects in G32 unduly benefit from the unfamiliar stimulus of
training with a higher RT volume and because the lower-body mus-
cles are more responsive to this (28,34), the muscle strength gain was
more influenced by this new stimulus. It is also possible that periodi-
zationofRTvolumemightprovide ameans tomaintain thenoveltyof
the stimulus and thus promote a continued gain over time; this hy-
pothesis is worthy of additional investigation. In this context, it is
recommended that future researches in resistance-trained subjects
consider an extended familiarizationperiod (3–4weeks) of all subjects
performing the same lower volume routine. Third, the small sample
size affected statistical power. As is the case in most longitudinal RT
studies, a high degree of interindividual variability was noted among
subjects, which limited the ability to detect a significant difference in
several outcome measures. Despite this limitation, the analysis of ESs
provides a good basis for drawing inferential conclusions from the
results. It is recommended that future researches for the investigation
of a dose-response relationship among trained individuals used lager
sample sizes. Finally, the findings of this study are specific to
resistance-trained men and, therefore, cannot necessarily be general-
ized to other populations including adolescents, women, and the el-
derly. It is possible that the higher RT volumes may not be as well
tolerated in these individuals and perhaps could hasten the onset of
overtrainingwhen combinedwith a high intensity of effort and longer
training periods. Future research is required to determine the volume-
related responses to RT across different populations.
Practical Applications
This study provides evidence that a higher RT volume (32
weekly sets per muscle group) augments lower-body muscular
strength; however, the RT volume does not seem to have any
additive effect on upper-body muscular strength. Alternatively,
a dose-response relationship was observed for the increase in
muscle hypertrophy, with a greater gain achieved with the
higher RT volume. It is conceivable that for those who wish to
maximize muscle strength and hypertrophy as a primary goal,
periodization of RT volume over the course of a long-term
training cycle to achieve higher volumes, interspersed with
lower RT volumes, may be an adequate approach. Such a pe-
riodization strategy would maintain the novelty of the training
stimulus and provide deloading phases aimed at promoting
recovery, thus facilitating a continuous improvement in neu-
romuscular performance and muscular hypertrophy.
Figure 4. Correlation coefficients (with 95% confidence
intervals) between accumulated total load lifted and absolute
differences (raw value) from pre– to post–8 weeks in de-
pendent variables. All subjects were pooled together (n5 27).
The grey area represents trivial correlation (see Methods).
Figure 3.Weekly total load lifted (TLL) of subjects during the 8
weeks of intervention training (3A). Delta (Δ) absolute and
relative (%) differences of the TLL (kgf) at week 8 minus week
1. A) different from G16; (B) different from G24.
Resistance-Training Volume (2019) 00:00
8
Copyright © 2019 National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
Acknowledgments
The authors acknowledge for the support of Conselho Nacional
deDesenvolvimentoCientı́fico e Tecnologia—Brazil (CNPq), and
Coordenação de Aperfeiçoamento de Pessoal deNı́vel Superior—
Brazil (CAPES).
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