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Resistance Training Volume Enhances Muscle
Hypertrophy but Not Strength in Trained Men
BRAD J. SCHOENFELD
1
, BRET CONTRERAS
2
, JAMES KRIEGER
3
, JOZO GRGIC
4
, KENNETH DELCASTILLO
1
,
RAMON BELLIARD
1
, and ANDREW ALTO
1
1
Department of Health Sciences, CUNY Lehman College, Bronx, NY;
2
Sport Performance Research Institute, AUT University,
Auckland, NEW ZEALAND;
3
Weightology, LLC, Redmond, WA; and
4
Institute for Health and Sport (IHES), Victoria
University, Melbourne, AUSTRALIA
ABSTRACT
SCHOENFELD, B. J., B. CONTRERAS, J. KRIEGER, J. GRGIC, K. DELCASTILLO, R. BELLIARD, and A. ALTO. Resistance
Training Volume Enhances Muscle Hypertrophy but Not Strength in Trained Men. Med. Sci. Sports Exerc., Vol. 51, No. 1, pp. 94–103,
2019. Purpose: The purpose of this study was to evaluate muscular adaptations between low-, moderate-, and high-volume resistance
training protocols in resistance-trained men. Methods: Thirty-four healthy resistance-trained men were randomly assigned to one of three
experimental groups: a low-volume group performing one set per exercise per training session (n= 11), a moderate-volume group
performing three sets per exercise per training session (n= 12), or a high-volume group performing five sets per exercise per training
session (n= 11). Training for all routines consisted of three weekly sessions performed on nonconsecutive days for 8 wk. Muscular
strength was evaluated with one repetition maximum (RM) testing for the squat and bench press. Upper-body muscle endurance was
evaluated using 50% of subjects bench press 1RM performed to momentary failure. Muscle hypertrophy was evaluated using B-mode
ultrasonography for the elbow flexors, elbow extensors, mid-thigh, and lateral thigh. Results: Results showed significant preintervention
to postintervention increases in strength and endurance in all groups, with no significant between-group differences. Alternatively, while
all groups increased muscle size in most of the measured sites from preintervention to postintervention, significant increases favoring the
higher-volume conditions were seen for the elbow flexors, mid-thigh, and lateral thigh. Conclusions: Marked increases in strength and
endurance can be attained by resistance-trained individuals with just three 13-min weekly sessions over an 8-wk period, and these gains
are similar to that achieved with a substantially greater time commitment. Alternatively, muscle hypertrophy follows a dose–response
relationship, with increasingly greater gains achieved with higher training volumes. Key Words: VOLUME, DOSE–RESPONSE
RELATIONSHIP, STRENGTH TRAINING, HYPERTROPHY, SINGLE SET
Resistance training (RT) is the primary exercise in-
tervention for increasing muscle mass in humans. It
is theorized that the volume of training performed in
a RT bout—herein determined by the formula: repetitions //
sets (1)—plays a significant role in chronic muscular adapta-
tions such as muscle size and strength (2). As compared with
single-set routines, acute studies indicate that performing
multiple sets augments the phosphorylation of p70S6 kinase
and muscle protein synthesis (MPS), suggesting that higher
volumes of training are warranted for maximizing the hy-
pertrophic response (3,4). However, although acute signaling
and MPS studies can help to generate hypotheses as to po-
tential long-term RT responses, longitudinal studies directly
assessing hallmark adaptations, such as muscular strength and
muscle hypertrophy, are necessary to draw evidence-based
conclusions for exercise prescription (5).
When evaluating the results of longitudinal research on
the topic, many of the studies have failed to show statistically
significant differences in hypertrophy between lower and
higher RT volumes. However, low sample sizes in these studies
raise the potential for type II errors, invariably confounding the
ability to draw conclusive inferences regarding probability. A
recent meta-analysis showed a dose–response relationship be-
tween the total number of weekly sets and increases in muscle
growth (6). However, the analysis was only able to determine
dose–response effects up to 10 total weekly sets per muscle
group due to the paucity of research on higher-volume RT
programs. Thus, it remains unclear whether training with even
higher volumes would continue to enhance hypertrophic
Address for correspondence: Brad J. Schoenfeld, Ph.D., CUNY Lehman
College, 250 Bedford Park Blvd West, Bronx, NY 10468; E-mail:
brad@workout911.com.
Submitted for publication June 2018.
Accepted for publication August 2018.
0195-9131/19/5101-0094/0
MEDICINE & SCIENCE IN SPORTS & EXERCISE
Ò
Copyright Ó2018 The Author(s). Published by Wolters Kluwer Health, Inc.
on behalf of the American College of Sports Medicine. This is an open-
access article distributed under the terms of the Creative Commons
Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-
ND), where it is permissible to download and share the work provided it
is properly cited. The work cannot be changed in any way or used com-
mercially without permission from the journal.
DOI: 10.1249/MSS.0000000000001764
94
APPLIED SCIENCES
adaptations and, if so, at what point these results would pla-
teau.Anaddedlimitationtothesefindingsisthatonlytwoof
the 15 studies that met inclusion criteria were carried out in
individuals with previous RT experience. There is compelling
evidence that resistance-trained individuals respond differently
than those who are new to RT (7). A ‘‘ceiling effect’’ makes it
progressively more difficult for trained lifters to increase
muscle mass, thereby necessitating more demanding RT pro-
tocols to elicit further muscular gains. Indeed, there is
emerging evidence that consistent RT can alter anabolic in-
tracellular signaling (8), indicating an attenuated hypertrophic
response. Thus, findings from untrained individuals cannot
necessarily be generalized to a resistance-trained population.
A dose–response pattern has also been proposed for RT
volume and muscular strength gains. A recent meta-analysis
on the topic by Ralston et al. (9) showed that moderate to
high weekly training volumes (defined as set volume) are
more effective for strength gains as compared with lower
training volumes. It should be noted, however, that only two
of the included studies used a dose–response study design
among trained individuals. In a sample of 32 resistance-
trained men, Marshall et al. (10) demonstrated that higher-
volume training produces both faster and greater strength
gains as compared with lower-volume training. In contrast to
these results, Ostrowski et al. (11) conducted a study among
27 trained men and reported similar changes in muscular
strength between low-, moderate- and high-volume training
groups. Both of these studies included resistance-trained
men, yet they observed different findings. It, therefore, is
evident that further work among trained individuals is
warranted to better elucidate this topic.
Given the existing gaps in the current literature, the pur-
pose of this study was to evaluate muscular adaptations be-
tween low-, moderate-, and high-volume RT protocols in
resistance-trained men. This design afforded the ability to
glean insight into the benefits of the respective training
protocols while taking into account the time efficiency of
training. Based on previous research and meta-analytical
data, we hypothesized that there would be a graded response
to outcomes, with increasing gains in muscular strength and
hypertrophy seen in low-, moderate-, and high-volume pro-
grams, respectively.
METHODS
Subjects
Subjects were 45 healthy male volunteers (height, 175.0 T
7.9 cm; weight, 82.5 T13.8 kg; age, 23.8 T3.8 yr; RT ex-
perience, 4.4 T3.9 yr) recruited from a university popula-
tion. This sample size was justified by a priori power
analysis in G*power using a target effect size (ES) of f=0.25,
alpha of 0.05 and power of 0.80, which determined that
36 subjects were required for participation; the additional re-
cruitment accounted for the possibility of dropouts. Subjects
were required to meet the following inclusion criteria: 1)
males between the ages of 18 to 35 yr, 2) no existing
musculoskeletal disorders, 3) claimed to be free from con-
sumption of anabolic steroids or any other legal or illegal
agents known to increase muscle size for the previous year, 4)
experienced with RT, defined as consistently lifting weights at
least three times per week for a minimum of 1 yr.
Subjects were randomly assigned to one of three experi-
mental groups: a low-volume group (1SET) performing one
set per exercise per training session (n= 15), a moderate-
volume group (3SET) performing three sets per exercise per
training session (n= 15), or a high-volume group (5SET)
performing five sets per exercise per training session (n=15).
Using previously established criteria (12), this translated into
a total weekly number of sets per muscle group of six and
nine sets for 1SET, 18 and 27 sets for 3SET, and 30 and 45
sets for 5SET in the upper and lower limbs, respectively. The
number of sets was greater for the lower-body musculature as
compared to the upper-body musculature. Such a training
program was designed based on the claim that lower-body
muscles might require more training volume (as compared
with the upper body) to optimize muscular adaptations with
RT (13). Approval for the study was obtained from the
Lehman College Institutional Review Board (2017-0778).
Informed consent was obtained from all subjects before
beginning the study.
RT Procedures
The RT protocol consisted of seven exercises per session
targeting all major muscle groups of the body. The exercises
performed were: flat barbell bench press, barbell military
press, wide grip lateral pulldown, seated cable row, barbell back
squat, machine leg press, and unilateral machine leg extension.
These exercises were chosen based on their common inclusion in
bodybuilding- and strength-type RT programs (14,15). To pre-
vent confounding, subjects were instructed to refrain from
performing any additional resistance-type or high-intensity an-
aerobic training for the duration of the study.
Training for all routines consisted of three weekly ses-
sions performed on nonconsecutive days for 8 wk. Sets
consisted of 8 to 12 repetitions carried out to the point of
momentary concentric failure, that is, the inability to per-
form another concentric repetition while maintaining proper
form. The cadence of repetitions was carried out in a con-
trolled fashion, with a concentric action of approximately 1 s
and an eccentric action of approximately 2 s. Subjects were
afforded 90-s rest between sets. The time between exercises
was prolonged to approximately 120 s given the additional
time required for the setup of the equipment used in the
subsequent resistance exercise. The load was adjusted for
each exercise as needed on successive sets to ensure that
subjects achieved momentary failure in the target repetition
range. Thus, if a subject completed more than 12 repetitions
to momentary failure in a given set, the load was increased
based on the supervising researcher’s assessment of what
would be required to reach momentary failure in the desired
loading range; if less than eight repetitions were
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accomplished, the load was similarly decreased. All routines
were directly supervised by the research team to ensure
proper performance of the respective routines. Attempts
were made to progressively increase the loads lifted each
week to ensure that the subjects were exercising with as
much resistance as possible within the confines of maintaining
the target repetition range. Before training, subjects underwent
10 repetition maximum (RM) testing to determine individual
initial training loads for each exercise. Repetition maximum
testing was consistent with recognized guidelines as established
by the National Strength and Conditioning Association (14).
Dietary Adherence
To avoid potential dietary confounding of results, subjects
were advised to maintain their customary nutritional regi-
men and to avoid taking any supplements other than those
provided in the course of the study. Dietary adherence was
assessed by self-reported food records using a nutritional
tracking application (http://www.myfitnesspal.com), which
was collected for 5-d periods twice during the study: 1 wk
before the first training session (i.e., baseline) and during the
final week of the training protocol. Subjects were instructed
on how to properly record all food items and their respective
portion sizes consumed for the designated period of interest.
Each item of food was individually entered into the program,
and the program provided relevant information as to total
energy consumption, as well as amount of energy derived
from proteins, fats, and carbohydrates for each time period
analyzed. To help ensure that dietary protein needs were met,
subjects consumed a supplement on training days containing
24gproteinand1gcarbohydrate(Iso100HydrolyzedWhey
Protein Isolate; Dymatize Nutrition, Dallas, TX) under the
supervision of the research staff.
Measurements
Anthropometry. Subjects were told to refrain from
eating for 12 h before testing, eliminate alcohol consumption
for 24 h, abstain from strenuous exercise for 24 h, and void
immediately before the test. Height was measured to the
nearest 0.1 cm using a stadiometer. Body mass was mea-
sured to the nearest 0.1 kg on a calibrated scale (InBody
770; Biospace Co. Ltd., Seoul, Korea).
Muscle thickness. Ultrasound imaging was used to
obtain measurements of muscle thickness (MT), which
shows a high correlation with RT-induced changes in
muscle cross-sectional area as determined by the ‘‘gold
standard’’ magnetic resonance imaging (16). As reported by
others, correlations between magnetic resonance imaging
and ultrasound measurements amount to 0.89, 0.73, and 0.91
for elbow flexors, elbow extensors, and quadriceps MT, re-
spectively (17,18). The lead researcher, a trained ultrasound
technician, performed all testing using a B-mode ultrasound
imaging unit (ECO3; Chison Medical Imaging, Ltd, Jiang Su
Province, China). The technician applied a water-soluble
transmission gel (Aquasonic 100 Ultrasound Transmission
gel; Parker Laboratories Inc., Fairfield, NJ) to each measure-
ment site, and a 5- to 10-MHz ultrasound probe was placed
perpendicular to the tissue interface without depressing the
skin. When the quality of the image was deemed satisfactory,
the technician saved the image to hard drive and obtained MT
dimensions by measuring the distance from the subcutaneous
adipose tissue–muscle interface to the muscle–bone interface.
Measurements were taken on the right side of the body at four
sites: 1) elbow flexors, 2) elbow extensors, 3) mid-thigh (a
composite of the rectus femoris and vastus intermedius), and
4) lateral thigh (a composite of the vastus lateralis and vastus
intermedius). 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; mid- and lateral thigh measurements were taken
50% between the lateral condyle of the femur and greater
trochanter for the quadriceps femoris. In an effort to ensure
that swelling in the muscles from training did not obscure
results, images were obtained 48 to 72 h before commence-
ment of the study, as well as after the final RT session. This is
consistent with research showing that acute increases in MT
return to baseline within 48 h after an RT session (19). To
further ensure accuracy of measurements, three images
were obtained for each site and then averaged to obtain a
final value. The between-day repeatability of ultrasound
tests was assessed in a pilot study in a sample of 10 young
resistance-trained men. The test–retest intraclass correla-
tion coefficient (ICC) from our lab for thickness measure-
ment of the elbow flexors, elbow extensors, mid-thigh and
lateral thigh as assessed on consecutive days are 0.976,
0.950, 0.944 and 0.998, respectively. The standard error of
the measurement (SEM) for elbow flexor, elbow extensor,
mid-thigh, and lateral thigh MT was 0.70, 0.83, and 1.09,
and 0.34 mm, respectively.
Maximal Strength Assessments
Muscle strength. Upper- and lower-body strength was
assessed by 1RM testing in the barbell parallel back squat
(1RM
SQUAT
) and flat barbell bench press (1RM
BENCH
) ex-
ercises. These exercises were chosen because they are well
established as measures of maximal strength. Subjects
reported to the laboratory having refrained from any exercise
other than activities of daily living for at least 48 h before
baseline testing and at least 48 h before testing at the con-
clusion of the study. RM testing was consistent with rec-
ognized guidelines established by the National Strength and
Conditioning Association (14). In brief, subjects performed
a general warm-up before testing that consisted of light car-
diovascularexerciselastingapproximately5to10min.A
specific warm-up set of the given exercise of 8 to 10 repetitions
was performed at ~50% of subjects_perceived 1RM followed
by one to two sets of two to three repetitions at a load corre-
sponding to approximately 60% to 80% 1RM. Subjects then
performed sets of one repetition of increasing weight for 1RM
determination. Three- to 5-min rest was provided between each
http://www.acsm-msse.org96 Official Journal of the American College of Sports Medicine
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successive attempt. All 1RM determinations were made within
five trials. Subjects were required to reach parallel in the
1RM
SQUAT
for the attempt to be considered successful as de-
termined by a squat beeper (SquatRight); confirmation of squat
depth was obtained by a research assistant positioned laterally
to the subject to ensure accuracy. Successful 1RM
BENCH
was
achieved if the subject displayed a five-point body contact po-
sition (head, upper back, and buttocks firmly on the bench with
both feet flat on the floor) and executed full-elbow extension.
1RM
SQUAT
testing was conducted before 1RM
BENCH
with a
5-min rest period separating tests. Recording of foot and hand
placement was made during baseline 1RM testing and then
used for poststudy performance. All testing sessions were
supervised by the research team to achieve a consensus for
success on each trial. The repeatability of strength tests was
assessed on two nonconsecutive days in a pilot study of six
young, resistance-trained men. The ICC for the 1RM
BENCH
and 1RM
SQUAT
was 0.98 and 0.93, respectively. The SEM
for these measures are 2.0 and 2.4 kg, respectively.
Muscle endurance. Upper-body muscular endurance
was assessed by performing the bench press using 50% of
the subject_s initial 1RM in the bench press (50% BP) for as
many repetitions as possible to momentary failure with
proper form. Successful performance was achieved if the
subject displayed a five-point body contact position (head,
upper back, and buttocks firmly on the bench with both feet
flat on the floor) and executed a full lock-out. Muscular
endurance testing was carried out after assessment of muscular
strength to minimize effects of metabolic stress interfering with
performance of the latter. The repeatability of the muscular
endurance test was assessed on two nonconsecutive days in a
pilot study of seven young resistance-trained men. The ICC
for the 50% BP was 0.93, and the SEM was 0.99 repetitions.
Statistical Analyses
Data were modeled using both a frequentist and Bayesian
approach. The frequentist approach involved a using an
ANCOVA on the change scores, with group (one, three, or
five sets) as the factor and with the baseline value as a co-
variate. The Bayesian approach involved a JZS Bayes Factor
ANCOVA with default prior scales. In the case of a signif-
icant ANCOVA effect, control for the familywise error rate
of multiple testing was performed using a Holm–Bonferroni
correction. In the Bayes Factor ANCOVA, the posterior odds
were corrected for multiple testing by fixing to 0.5 the prior
probability that the null hypothesis holds across all comparisons.
Analyses were performed using JASP 0.8.6 (Amsterdam, The
Netherlands). Effects were considered significant at Pe0.05.
Bayes factors for effects were interpreted as ‘‘weak,’’ ‘‘positive,’’
‘‘strong,’’ or ‘‘very strong’’ according to Raftery (20). Data are
reported as x¯TSD unless otherwise specified.
RESULTS
Eleven subjects dropped out during the course of the study,
resulting in a total sample of 34 subjects (1SET, n= 11; 3SET,
n= 12; 5SET, n= 11). Reasons for dropouts were as follows:
personal reasons, 4; noncompliance, 3; training-related injury,
2; injury unrelated to training, 2. Thus, the study was slightly
underpowered based on initial power analysis. All subjects
included in the final statistical analysis completed 980% of
sessions with an overall average attendance of 94%. Average
training time per session was approximately 13 min for 1SET,
approximately40minfor3SET,andapproximately68min
for 5SET. Figure 1 depicts the data collection process in
flowchart format.
Squat 1RM. We were unable to gauge successful 1RM
in one of the subjects from 1SET and one of the subjects from
3SET in the allotted number of trials, and thus had to exclude their
data from analysis. There was no significant difference between
groups in squat 1RM improvement, and evidence favored the
null model (P=0.22;BF
10
G1; Table 1; Figure 2A).
Bench 1RM. There was no significant difference between
groups in bench 1RM improvement, and there was weak
evidence favoring a difference in pretest bench 1RM over a
group difference in bench press improvement (P=0.15;BF
10
G1
for group differences; Table 1; Figure 2B).
Bench endurance. There was no significant difference
between groups in bench endurance improvement, and evi-
dence favored the null model (P= 0.52; BF
10
G1; Table 1;
Figure 2C).
Elbow flexor thickness. There was a significant dif-
ference between groups in improvements in bicep thick-
ness, and positive evidence in favor of a group effect over
the null (P=0.02;BF
10
= 3.04; Table 1; Figure 3A). Post hoc
comparisons showed a significant difference between one
and five sets (Table 1). There was positive evidence in fa-
vor of five sets compared with one set (BF
10
= 4.71) and
weak evidence in favor of three sets compared with one set
(BF
10
= 1.30). Evidence did not favor three sets versus five
sets (BF
10
=0.60).
Elbow extensor thickness. We were unable to achieve
satisfactory imaging in one of the subjects from 3SET, and
thus had to exclude his data from analysis. There was no
significant difference between groups in the improvement
in triceps thickness, and evidence favored the null model
(P= 0.19; BF
10
G1; Table 1; Figure 3B).
Mid-thigh thickness. We were unable to achieve sat-
isfactory imaging in three of the subjects from 3SET and
two of the subjects from 5SET, and thus had to exclude their
data from analysis. There was a significant difference between
groups in improvements in rectus femoris thickness, and positive
evidence in favor of a group effect over the null (P=0.02;BF
10
=
8.51; Table 1; Figure 3C). Post hoc comparisons showed a
significant difference between one and five sets (Table 1).
There was positive evidence in favor of five sets compared to
one set (BF
10
= 13.65) and weak evidence in favor of five
sets compared with three sets (BF
10
= 2.34). Evidence did
not favor one set versus three sets (BF
10
=0.51).
Lateral thigh thickness. There was a significant dif-
ference between groups in improvements in vastus lateralis
thickness, and strong evidence in favor of both a group
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effect and pretest effect over the null (P= 0.006; BF
10
=
63.87; Table 1; Figure 3D). Post hoc comparisons showed a
significant difference between one and five sets (Table 1).
There was strong evidence in favor of five sets compared to
one set (BF
10
= 38.14) and weak evidence in favor of three
sets compared with one set (BF
10
= 1.42) and five sets
compared to three sets (BF
10
= 2.25).
Diet. There were no significant differences between
groups in changes in self-reported kilocalorie or macronu-
trient intake (Table 1). There was positive evidence in favor
TABLE 1. Data of study outcomes.
Outcomes Group
Pre,
Mean TSD
Post,
Mean TSD
Unadjusted,
$(TSD)
P
(Group)
BF
10
(Group)
BF
10
(Pre)
BF
10
(Group + Pre)
Baseline
Adjusted $(CI)*
Squat 1RM (kg) 1 104.5 T14.2 123.4 T12.9 18.9 T6.0 0.22 0.78 0.82 0.53 18.6 (13.7 to 23.4)
3 114.9 T26.0 128.5 T24.7 13.6 T5.4 14.1 (9.5 to 18.7)
5 106.6 T24.0 126.2 T25.0 19.6 T10.0 19.5 (14.9 to 24.0)
Bench 1RM (kg) 1 93.6 T16.1 102.9 T15.2 9.3 T4.4 0.15 0.71 1.35** 0.99 9.3 (6.9 to 11.9)
3 96.4 T21.2 102.1 T20.1 5.7 T5.8 5.9 (3.4 to 8.4)
5 91.1 T20.9 97.9 T20.0 6.8 T2.3 6.6 (4.0 to 9.2)
Bench endurance 1 25.1 T3.6 28.2 T4.6 3.1 T3.9 0.52 0.30 0.37 0.11 3.1 (0.8 to 5.4)
3 23.7 T5.2 28.0 T5.6 4.3 T4.1 4.2 (2.0 to 6.4)
5 26.2 T4.3 31.0 T6.1 4.8 T2.9 4.9 (2.6 to 7.3)
Biceps thickness (mm) 1 42.6 T4.3 43.3 T5.1 0.7 T2.0 0.02*** 3.04** 0.33 1.03 0.7 (j0.4 to 1.8)
a
3 44.6 T5.9 46.7 T5.8 2.1 T1.6 2.1 (1.1 to 3.2)
ab
5 41.9 T3.6 44.8 T4.1 2.9 T1.7 2.9 (1.8 to 4.0)
b
Triceps thickness (mm) 1 47.2 T4.5 47.7 T4.6 0.6 T2.0 0.19 0.66 0.35 0.33 0.5 (j1.0 to 2.1)
3 48.4 T6.2 49.8 T6.3 1.4 T3.1 1.4 (j0.1 to 3.0)
5 47.1 T3.5 49.7 T4.9 2.6 T2.3 2.6 (1.0 to 4.1)
Rectus femoris thickness (mm) 1 59.7 T6.7 61.7 T5.5 2.0 T2.6 0.02*** 8.51** 1.74 6.75 2.2 (0.3 to 4.2)
a
3 57.9 T8.1 61.0 T8.7 3.0 T3.1 3.1 (1.0 to 5.2)
ab
5 54.4 T3.4 61.2 T4.5 6.8 T3.6 6.4 (4.2 to 8.6)
b
Vastus lateralis thickness (mm) 1 57.5 T6.0 60.4 T6.3 2.9 T1.9 0.006*** 38.14 5.81 63.87** 3.1 (1.6 to 4.5)
a
3 57.9 T8.0 62.5 T7.0 4.6 T2.3 4.9 (3.5 to 6.3)
ab
5 52.4 T6.2 59.6 T5.8 7.2 T3.0 6.8 (5.2 to 8.3)
b
Values are in mean TSD.
*Adjusted means are significantly different if superscript letters are different, based on all pairwise comparisons with a Holm adjustment.
**Preferred model based on highest BF
10
Q1.
***Significant at Pe0.05.
95% CI, 95% confidence interval.
FIGURE 1—Flowchart of data collection process.
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of baseline differences in self-reported kilocalorie intake
(BF
10
= 10.26; Table 1), but only weak evidence in favor of
baseline differences in self-reported macronutrient intake
(1 GBF
10
G3, Table 2).
DISCUSSION
The present study provided several important findings
that further our knowledge of the effect of RT volume on
muscular adaptations in resistance-trained individuals.
Specifically, changes in muscle strength and muscle en-
durance were similar regardless of the volume performed
when training in a moderate loading range (8–12 repetitions
per set); alternatively, higher volumes of training in this
loading range were associated with greater increases in
markers of muscle hypertrophy. We discuss the particulars
of these findings, as well as the study_s limitations, in the
subheadings below.
FIGURE 3—Prestudy to poststudy changes in MT for each condition. (A) Elbow flexors; (B) elbow extensors; (C) mid-thigh; (D) lateral thigh. All
values are in millimeters.
FIGURE 2—Prestudy to poststudy changes in muscle strength and endurance for each condition. (A) 1RM bench press; (B) 1RM squat; (C) upper
body muscular endurance. Values for 1RM
BENCH
and RM
SQUAT
are in kilograms; values for 50%BP are in repetitions.
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Muscle strength. Contrary to our initial hypothesis,
gains in muscular strength were strikingly similar across
conditions, with volume showing no differential effects on
1RM
SQUAT
or 1RM
BENCH
. Indeed, the results presented
herein indicate that the 1SET training condition may be sim-
ilarly effective at increasing muscular strength as performing
three or five sets per exercise. These findings indicate
that resistance-trained individuals can markedly enhance
levels of strength by performing only ~39 min of weekly
RT, with gains equal to that achieved in a fivefold greater
time commitment.
Our results are somewhat in contrast to the meta-analysis by
Ralston et al. (9). The authors reported that for strength in
multijoint exercises (as used in this study), moderate-to-high
weekly set volume routines (defined as six or more sets per
week) are more effective than low weekly set volume routines
(defined as five sets or less per week). Albeit, it should be made
clear that the ES difference was rather small (ES, 0.18; 95%
confidence interval, 0.01–0.34). Although in this study, the
1SET group did perform the least amount of volume, their total
weekly volume of six to nine sets per muscle group would be
classified as a moderate volume in the Ralston et al. (9) review.
To allow direct comparison of our results with the meta-
analysis mentioned-above an additional group that trained with
five or fewer sets per week would need to be included. Also, it
needs to be pointed out that the studies included in the meta-
analysis by Ralston et al. (9) used exercise prescriptions and
loading schemes that were different to those used in the present
study. Given the differences in the weekly set configurations,
it is difficult to compare these results with the meta-analysis by
Ralston et al. (9).
Three individual studies thus far have used a comparable
study design. Radaelli et al. (21) compared the effects of 6, 18,
and 30 weekly sets per muscle group. All groups increased
strength postintervention in all four tested exercises. However,
for the bench press and lat-pulldown exercises, the 30 weekly
set group experienced greater increases than the two other
groups. Given that their subjects did not have any RT experience
it might be that the greater strength gains in the 30 weekly set
group are due to the greater opportunities to practice the ex-
ercise and thus an enhanced ‘‘learning’’ effect (22). Also, their
intervention lasted 6 months, whereas the present study had a
duration of 8 wk. It might be that higher training volumes
become of greater importance for strength gains over longer
time courses; future studies exploring this topic using longer
duration interventions are needed to confirm this hypothesis.
Marshall et al. (10) examined the effects of three different
doses of volume on barbell back squat strength. The authors
compared the effect of 2, 8, and 16 weekly sets of squats (the
only resistance exercise for lower-body) and reported that
the 16 weekly sets group increased strength significantly
greater than the two weekly sets group. Although the authors
did include trained men, the main part of the training inter-
vention lasted 6 wk with a twice-weekly frequency, which
differs from the present study design. The authors used mid-
point testing after 3 wk of training and found that the 8 and
16 weekly set volume groups increased strength from baseline
while the two-weekly set group did not. Following the
remaining 3 wk, all groups increased strength from their
baseline values. However, the 16 weekly set group had greater
increases than the 2, but not the eight set group. Although we
did not use midpoint testing, it remains possible that the
higher-volume groups increased strength to a greater point
during the initial phases (e.g., in the first 4 wk), and that
these gains then leveled off between the groups by the end
of the intervention. Furthermore, it might be that subjects in
the high-volume group approached an overtraining (i.e.,
nonfunctional overreaching) status toward the end of the
training program, which might have impacted their levels of
strength at the postassessment. Future studies done on this
topic might consider using multiple strength testing points
during the intervention to explore if there are any differ-
ences in the time course of muscular strength accrual be-
tween different volumes of training.
Ostrowski et al. (11) reported that after 10 wk of training,
all groups increased upper and lower-body strength with no
significant between-group differences. Taken together with
the findings of Ostrowski et al. (11), our results would imply
that for strength improvements, there is a certain threshold
of volume that can be used in a training program, over which
further increases in volume are not advantageous, and might
only delay recovery from exercise. From a strength perspective,
TABLE 2. Nutritional data.
Outcome Groups Pre, Mean TSD Post, Mean TSD Unadjusted $(TSD) P(Group) BF
10
(Group) BF
10
(Pre) BF
10
(Group + Pre) Baseline Adjusted $(CI)*
Kcal 1 1752 T608 1790 T601 38 T445 0.31 0.48 10.26** 4.70 j75 (j417 to 268)
3 2041 T642 2198 T356 157 T703 175 (j130 to 479)
5 2190 T617 1961 T812 j229 T535 j144 (j468 to 179)
Protein (g) 1 114 T48 120 T49 7 T40 0.94 0.23 1.06** 0.23 3 (j28 to 34)
3 128 T46 127 T48 j1T48 0 (j28 to 28)
5 131 T48 125 T71 j6T56 j4(j33 to 25)
Carbohydrate (g) 1 195 T101 148 T103 j47 T79 0.24 0.31 2.94** 1.38 j55 (j100 to j11)
3 227 T91 205 T74 j22 T82 j20 (j60 to 20)
5 239 T128 229 T119 j10 T63 j4(j47 to 38)
Fat (g) 1 60 T30 75 T51 14 T53 0.16 0.52 1.39** 0.96 13 (j9to35)
367T40 89 T39 22 T33 23 (3 to 44)
560T27 57 T24 j4T14 j5(j26 to 16)
Values are in mean TSD.
*Adjusted means are significantly different if superscript letters are different, based on all pairwise comparisons with a Holm adjustment.
**Preferred model based on highest BF
10
Q1.
http://www.acsm-msse.org100 Official Journal of the American College of Sports Medicine
APPLIED SCIENCES
the findings would imply that a lower training volume routine
is equally effective to a higher training volume routine. Fur-
thermore, a lower-volume approach would be a more time-
efficient way of training, which might ultimately facilitate
better adherence given that time is commonly purported as a
factor influencing training adherence (23,24). Indeed, the
subjects in the 1SET group, on average, trained approxi-
mately 13 min per training session, whereas the 3SET and
5SET groups trained approximately 40 and 68 min, respec-
tively. It should be made clear that our results are specific to
training in the 8 to 12 RM range. It is possible that a different
pattern would emerge if the subjects trained with higher (or
lower) loads. For instance, training in the 1 to 5 RM zone
might require more volume, given that there would be less
‘‘practice’’ with a lower repetition range. Future studies,
therefore, might consider using a more strength-specific rep-
etition range to further explore this topic.
Muscle hypertrophy. The results of the present study
show a graded dose–response relationship between training
volume and muscle hypertrophy in a sample of resistance-
trained men. Our findings essentially mirror recent meta-
analytic data showing a dose–response relationship between
volume and hypertrophy (6). The present study indicates
that substantially greater training volumes may be beneficial
in enhancing muscle growth in those with previous RT ex-
perience, at least over an 8-wk training period. Hypertrophy
for three of the four measured muscles was significantly
greater for the highest versus lowest volume condition. Only
the elbow extensors did not show statistically greater in-
creases in MT between conditions. However, only the 5SET
condition showed a significant prestudy to poststudy in-
crease in elbow extensor growth, whereas measures of hy-
pertrophy in the lower volume conditions (i.e., 1SET and
3SET groups) were not statistically different. Moreover, a
dose–response relationship was seen for the magnitude of
effect in elbow extensor thickness changes, with ES values
of 0.12, 0.30, and 0.55 for the low-, moderate-, and high-
volume conditions, respectively.
Most previous researches investigating the effects of
varying RT volumes on muscular adaptations have been
carried out in those without RT experience. Only one pre-
vious study endeavored to examine the dose–response rela-
tionship (i.e., a minimum of three different set volumes)
between training volume and muscle growth in resistance-
trained individuals using site-specific measures of hyper-
trophy (11). In the 10-wk study, resistance-trained men were
allocated either to a: (a) low-volume group (three to seven
sets per muscle group per week); (b) moderate-volume
group (6–14 sets per muscle group per week); or (c) high-
volume group (12–28 sets per muscle group per week).
Results showed that percent changes and ES for muscle
growth in the elbow extensors and quadriceps femoris fa-
vored the high-volume group. However, no statistically
significant differences were noted between groups. When
comparing the results of Ostrowski et al. (11) to the present
study, there were notable similarities that lend support to the
role of volume as a potent driver of hypertrophy. Changes in
triceps brachii MT in Ostrowski et al. (11) study were 2.2%
for the lowest volume condition (seven sets per muscle per
week) and 4.7% for the highest-volume condition (28 sets
per muscle per week). Similarly, our study showed changes
in elbow extensor MT of 1.1% versus 5.5% for the lowest
(six sets per muscle per week) versus highest (30 sets per
muscle per week) volume conditions, respectively. Regard-
ing lower-body hypertrophy, Ostrowski et al. (11) showed
an increase of 6.8% in quadriceps MT for the lowest volume
condition (three sets per muscle per week) while growth in
the highest volume condition (12 sets per muscle per week)
was 13.1%. Again, these findings are fairly consistent with
those of the present study, which found an increase in mid-
thigh hypertrophy of 3.4% versus 12.5% and lateral thigh
hypertrophy of 5.0% versus 13.7% in the lowest and highest
volume conditions, respectively. It should be noted that the
lower-body volume was substantially greater in our study
for all conditions compared to Ostrowski et al. (11). Inter-
estingly, the group performing the lowest volume for the
lower-body performed nine sets in our study, which ap-
proaches the highest volume condition in Ostrowski et al.
(11), yet much greater levels of volume were required to
achieve similar hypertrophic responses in the quadriceps.
The reason for these discrepancies remains unclear.
Muscle endurance. All conditions showed similar
improvements in the test used for assessing muscular
endurance (i.e., the 50%BP test). To the best of our
knowledge, this is the first study that investigated the dose–
response effects of training volume on muscular endurance
adaptations in trained men. Similar to the findings presented
for strength, all groups increased muscular endurance from
pre-to-post with no significant between-group differences.
These findings indicate that training for improvements in
muscular abilities such as strength and muscular endurance
warrants a different volume prescription than when the
training goal is muscular hypertrophy. These differences in
the dose–response curves might be because muscular abil-
ities such as endurance have a significant skill component to
it. In other words, adaptations such as muscular endurance,
are, to a certain extent, influenced by motor learning (i.e.,
individuals learn the specific patterns of muscle recruitment
associated with performance of a given task) (25). Indeed,
studies that utilized training programs in which one group
trained with a repetition range that mimics the strength test,
while the other group trained with a repetition range which
was more similar to the endurance test, show that the latter
had greater improvements in muscular endurance; albeit, not
in all tested muscle groups (22). Furthermore, it is also rele-
vant to emphasize that the participants in all of the three
training groups trained used similar loading conditions.
Therefore, although we did not directly assess this variable,
all of the participants did likely experience similar levels of
discomfort associated with exercise (26). Level of discomfort
might be an important variable to consider given that the
ability to better tolerate discomfort may contribute to the
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increase in high-intensity exercise tolerance (exercise such as
the 50%BP test) (27). Thus, given that the discomfort with
training was likely similar between the groups, this might
explain the comparable increases in muscular endurance in all
three groups. Future studies done on this topic may wish to
explore this hypothesis further.
To the best of our knowledge, only one study examined the
dose–response effects between volume and muscular endur-
ance adaptations; albeit, this work was done in untrained in-
dividuals. In their study, Radaelli et al. (21) reported the 16-set
and 30-set groups increased muscular endurance pre-to-post
intervention as assessed by the 20 RM bench press test. The
increases in the 30-set group were greater than in the 16-set
group, and also, the increase in the 16-set group was greater
than the values observed in the 6-set group. For lower-body,
there was a significant increase in muscular endurance in all
groups, and the greatest increase was seen in the 30-set group.
Again, as with strength, it might be that more practice in the
higher-volume group resulted in greater gains in muscular
endurance. Given that the Radaelli et al. (21) study included
untrained individuals and their training program lasted
for 6 months, the comparison of their results with the results of
the present study remains limited. Also, in the present study,
we assessed only upper-body muscular endurance. Therefore,
these results cannot necessarily be generalized to the lower-
body musculature. Future work among trained individuals on
this topic is warranted.
Limitations. The study had several limitations that must
be taken into account when attempting to draw evidence-
based inferences. First, all subjects reported performing
multiset routines before the onset of the study and a majority
did not regularly train to momentary failure. It is unclear
how the novelty of altering these variables affected the re-
spective groups. Second, the upper-body musculature was
trained exclusively with multijoint exercises. These exer-
cises involve extensive involvement of the elbow flexors
and elbow extensors, as shown in the significant arm muscle
hypertrophy achieved with their consistent use (28,29). In-
deed, research indicates similar changes both in upper arm
MT and circumference when performing multijoint versus
single-joint exercises in untrained and trained individuals,
respectively (30,31). That said, it remains possible that single-
joint exercises for the arm musculature may become more
important to hypertrophy when training with low volumes;
further study on the topic is warranted. Third, measurements
of MT were obtained only at the mid-portion of the muscle
belly. Although this region is often used as a proxy of
the overall growth of a given muscle, research indicates
that hypertrophy manifests in a regional-specific manner, with
greater gains sometimes seen at the proximal and/or distal
aspects (32,33). Although it is possible that differences in
training volumes may have resulted in differential segmental
hypertrophy of a given muscle that was not detected by our
assessment method, there does not appear to be a sound ra-
tionale by which this would occur from manipulating volume,
making it unlikely that this confounded results. Fourth, al-
though subjects were instructed not to perform any additional
exercise training during the study, we cannot entirely rule out
that they failed to follow our guidelines. Fifth, the study had a
relatively small sample size and thus may have been some-
what underpowered to detect significant changes between
groups in certain outcomes. Sixth, while ultrasound is a well-
established method of assessing changes in markers of mus-
cle hypertrophy, it is not clear how the magnitude of the
reported changes impact aesthetic appearance. Finally, find-
ings of our study are specific to young resistance-trained men
and, therefore, cannot necessarily be generalized to other
populations, including adolescents, women, and older adults.
CONCLUSIONS
The present study shows that marked increases in strength
can be attained by resistance-trained individuals with just
three 13-min sessions per week, and that gains are similar to
that achieved with a substantially greater time commitment
when training in a moderate loading range (8–12 repetitions
per set). This finding has important implications for those
who are time-pressed, allowing the ability to get stronger in an
efficient manner, and may help to promote greater exercise ad-
herence in the general public. Alternatively, we show that increases
in muscle hypertrophy follow a dose–response relationship, with
increasingly greater gains achieved with higher training volumes.
Thus, those seeking to maximize muscular growth need to allot a
greater amount of weekly time to achieve this goal. Further re-
search is warranted to determine how these findings apply to re-
sistance individuals in other populations, such as women and
the elderly. Volume does not appear to have any differential
effects on measures of upper-body muscular endurance.
The authors would like to extend our heartfelt thanks to the fol-
lowing research assistants, without whom this study could not have
taken place: Patricia Fuentes, Shamel Jaime, Andriy Karp, Francis
Turbi, Christian Morales, Paco Almanzar, Chris Morrison, Lexis Beato,
Chaochi Lee, Elisha Edwards, Shailyn Mock, Leila Nasr, Antoine
Steward, Miguel Villafone, Solyi Lee, Joseph Ohmer, Marisela Santana,
Chicneccu Forde, Jonathan Mejia, Martin Bueno, Kevin Carranza,
MaChris Dampor, Mark Cells, Jason Abas, Abdul Pressley, Jonathan Davila,
Griselda Acevedo and Maria Hernandez. The authors also wish to thank
Dymatize Nutrition for supplying the protein supplements used in the study.
Finally, the authors are grateful to Andrew Vigotsky for his advice and rec-
ommendations on the statistical analyses. The results of this study are
presented clearly, honestly, and without fabrication, falsification, or inap-
propriate data manipulation, and do not constitute endorsement by ACSM.
This study was supported by a PSC CUNY grant from the State of
New York.
The authors declare no conflicts of interest.
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