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Journal of Sports Sciences
ISSN: 0264-0414 (Print) 1466-447X (Online) Journal homepage: http://www.tandfonline.com/loi/rjsp20
Dose-response relationship between weekly
resistance training volume and increases in
muscle mass: A systematic review and meta-
analysis
Brad J. Schoenfeld, Dan Ogborn & James W. Krieger
To cite this article: Brad J. Schoenfeld, Dan Ogborn & James W. Krieger (2016): Dose-
response relationship between weekly resistance training volume and increases in
muscle mass: A systematic review and meta-analysis, Journal of Sports Sciences, DOI:
10.1080/02640414.2016.1210197
To link to this article: http://dx.doi.org/10.1080/02640414.2016.1210197
Published online: 19 Jul 2016.
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ARTICLE
Dose-response relationship between weekly resistance training volume and
increases in muscle mass: A systematic review and meta-analysis
Brad J. Schoenfeld
a
, Dan Ogborn
b
and James W. Krieger
c
a
Department of Health Science, Lehman College, Bronx, NY, USA;
b
Total Rehabilitation and Sports Injuries Clinic, Winnipeg, Canada;
c
Weightology,
LLC, Issaquah, WA, USA
ABSTRACT
The purpose of this paper was to systematically review the current literature and elucidate the effects of
total weekly resistance training (RT) volume on changes in measures of muscle mass via meta-regres-
sion. The final analysis comprised 34 treatment groups from 15 studies. Outcomes for weekly sets as a
continuous variable showed a significant effect of volume on changes in muscle size (P=0.002). Each
additional set was associated with an increase in effect size (ES) of 0.023 corresponding to an increase in
the percentage gain by 0.37%. Outcomes for weekly sets categorised as lower or higher within each
study showed a significant effect of volume on changes in muscle size (P=0.03); the ES difference
between higher and lower volumes was 0.241, which equated to a percentage gain difference of 3.9%.
Outcomes for weekly sets as a three-level categorical variable (<5, 5–9 and 10+ per muscle) showed a
trend for an effect of weekly sets (P=0.074). The findings indicate a graded dose-response relationship
whereby increases in RT volume produce greater gains in muscle hypertrophy.
ARTICLE HISTORY
Accepted 1 July 2016
KEYWORDS
Exercise volume;
hypertrophy; skeletal
muscle; cross sectional area;
muscle growth
Introduction
Prevailing exercise science theory posits that muscular adapta-
tions are maximised by the precise manipulation of resistance
training (RT) programme variables (Bird, Tarpenning & Marino
2005; Kraemer & Ratamess, 2004). Training volume, commonly
defined as sets × reps × load, is purported to be one of the
most critical variables in this regard. Current hypertrophy
training guidelines recommend the performance of 1–3 sets
per exercise for novice individuals with higher volumes (HV) of
3–6 sets per exercise advised for advanced lifters (American
College of Sports Medicine, 2009). These guidelines are based
on the perceived presence of a dose-response relationship
between volume and muscle growth (Krieger, 2010), with HV
eliciting greater hypertrophic gains.
Several studies have examined the acute response to dif-
ferent RT volumes. Burd et al. (2010) reported significantly
greater increases in myofibrillar protein synthesis with 3 sets
of unilateral leg extension exercise at 70% 1 repetition max-
imum (RM) compared to a single set. These results held true at
both 5 h and 29 h post-exercise. Phosphorylation of the
intracellular signalling proteins eukaryotic translation initiation
factor 2B epsilon and ribosomal protein S6 were also elevated
to a greater extent in the multiple set conditions. A follow-up
study by the same lab found that phosphorylation of AKT,
mTOR and P70S6K were all greater when participants per-
formed 3 sets of unilateral leg extension versus 1 set, although
results did not rise to statistical significance (Mitchell et al.,
2012). Similarly, Terzis et al. (2010) demonstrated a graded
dose-response relationship between volume and increases in
both p70S6k and ribosomal protein S6, with linearly increasing
elevations noted between 1, 3 and 5 sets of leg presses carried
out at 6RM. Interestingly, Kumar et al. (2012) found that
increases in RT volume magnified the acute response to a
greater extent in elderly compared to young individuals.
While the totality of these findings suggest an acute anabolic
superiority for HV of resistance exercise, it is important to note
that acute measures are not necessarily reflective of the long-
term accretion of muscle proteins (Mitchell et al., 2014). Thus,
the practical application of these results must be interpreted
with some degree of circumspection.
The results of longitudinal research on the dose-response
relationship between volume and muscle hypertrophy have
been conflicting, with some studies showing that HV produce
significantly greater adaptations (Correa et al., 2015; Radaelli,
Botton, et al., 2014; Radaelli, Fleck, et al., 2014; Rønnestad
et al., 2007; Sooneste, Tanimoto, Kakigi, Saga, & Katamoto,
2013; Starkey et al., 1996) and other studies reporting no
volume-based differences (Bottaro, Veloso, Wagner, & Gentil,
2011; Cannon & Marino, 2010; Galvao & Taaffe, 2005; McBride,
Blaak, & Triplett-McBride, 2003; Mitchell et al., 2012; Ostrowski,
Wilson, Weatherby, Murphy, & Little, 1997; Radaelli, Wilhelm,
et al., 2014; Rhea, Alvar, Ball, & Burkett, 2002; Ribeiro et al.,
2015). However, the small samples inherent in longitudinal
training studies often compromise statistical power, thereby
increasing the likelihood of a type II error. A meta-analysis of
effect sizes (ES) can help identify trends among conflicting
and/or underpowered studies and thus provide greater insight
as to whether hypertrophic benefits actually exist from per-
forming higher training volumes. A meta-analysis by Krieger
(2010) published in 2010 found a 40% greater ES difference
favouring the performance of multiple versus single set
CONTACT Brad J. Schoenfeld brad@workout911.com
JOURNAL OF SPORTS SCIENCES, 2016
http://dx.doi.org/10.1080/02640414.2016.1210197
© 2016 Informa UK Limited, trading as Taylor & Francis Group
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training. Moreover, there was a dose-response trend with 2–3
sets per exercise associated with a greater ES versus 1 set and
4–6 sets per exercise associated with a greater ES than a single
set. A caveat to these findings is that only 8 studies qualified
for inclusion at the time, and only 3 measured muscle-specific
growths with imaging techniques such as MRI and ultrasound.
Numerous studies have been carried out subsequent to pub-
lication of this meta-analysis, with many employing advanced
muscle-specific imaging modalities to address the importance
of training volume. Moreover, Krieger (2010) analysed only the
impact of the number of sets per session on muscle growth
whereas the total number of weekly sets completed may be a
more relevant marker of training volume.
Thus, the purpose of this paper was to systematically review
the current literature and elucidate the effects of total weekly
RT volume on changes in measures of muscle mass via meta-
regression. Based on previous meta-analytic data (Krieger,
2010), we hypothesised that there would be graded dose-
response relationship, with higher training volumes promoting
progressively superior hypertrophic results.
Methods
Inclusion criteria
Studies were deemed eligible for inclusion if they met the
following criteria: (1) were an experimental trial published in
an English-language-refereed journal; (2) directly compared
different daily RT volumes in traditional dynamic resistance
exercise using coupled concentric and eccentric actions at
intensities ≥65% 1RM without the use of external implements
(i.e., pressure cuffs, hypoxic chamber, etc.) and all other RT
variables equivalent; (3) measured morphologic changes via
biopsy, imaging and/or densitometry; (4) had a minimum
duration of 6 weeks and (5) used human participants without
musculoskeletal injury or any health condition that could
directly, or through the medications associated with the man-
agement of said condition, be expected to impact the hyper-
trophic response to resistance exercise (i.e., coronary artery
disease and angiotensin receptor blockers).
Search strategy
The systematic literature search was conducted in accordance
with the Preferred Reporting Items for Systematic Reviews and
Meta-Analyses (PRISMA) guidelines (Moher, Liberati, Tetzlaff,
Altman, & PRISMA Group, 2009). To carry out this review,
English-language literature searches of the PubMed, Sports
Discus and CINAHL databases were conducted from all time
points up until December 2014. Combinations of the following
keywords were used as search terms: “muscle”;“hypertrophy”;
“growth”;“cross sectional area”;“fat free mass”;“resistance
training”,“resistance exercise”,“multiple sets”,“single sets”,
“volume”and “dose response”.
A total of 1474 studies were evaluated based on search
criteria. To reduce the potential for selection bias, each study
was independently perused by two of the investigators (BJS
and DIO), and a mutual decision was made as to whether or
not they met basic inclusion criteria. Any inter-reviewer
disagreements were settled by consensus or consultation
with the third investigator. Of the studies initially reviewed,
36 were determined to be potentially relevant to the paper
based on information contained in the abstracts. Full text of
these articles was then screened and 15 were deemed suitable
for inclusion in accordance with the criteria outlined. The
reference lists of articles retrieved were then screened for
any additional articles that had relevance to the topic, as
described by Greenhalgh and Peacock (2005). Two additional
studies were subsequently identified in this manner, bringing
the total number of eligible studies to 17. After subsequent
review, two of the studies (Radaelli, Botton, et al., 2013;
Radaelli, Wilhelm, et al., 2013) were found to have used pre-
viously collected data so they were excluded from analysis.
Thus, the final number of studies included for analysis was 15
(see Figure 1). Table 1 summarises the studies analysed. All
studies included in the analysis received ethics approval from
the local Institutional Review Board.
Coding of studies
Studies were read and individually coded by two of the
investigators (BJS and DIO) for the following variables:
Descriptive information of participants by group including
sex, body mass index, training status (trained participants
were defined as those with at least one year regular RT
experience), stratified participant age (classified as either
young [18–29 years], middle-aged [30–49 years] or elderly
[50+ years]; whether the study was a parallel or within-
participant design; the number of participants in each
group; duration of the study; number of sets performed per
muscle group per session; total weekly training volume per
muscle group (number of sets per muscle group per ses-
sion × number of weekly sessions); type of morphologic
measurement (magnetic resonance imaging (MRI), ultra-
sound, biopsy, dual energy X-ray absorptiomety [DXA] and/
or air displacement plethysmography); region/muscle of
body measured (upper, lower or both) and whether hyper-
trophy measure was direct or indirect. Coding was cross-
checked between coders, and any discrepancies were
resolved by mutual consensus. To assess potential coder
drift, 30% of the studies were randomly selected for recoding
as described by Cooper et al. (Cooper, Hedges, & Valentine,
2009). Per case agreement was determined by dividing the
number of variables coded the same by the total number of
variables. Acceptance required a mean agreement of 0.90.
Calculation of ES
For each hypertrophy outcome, an ES was calculated as the
pre-test–post-test change, divided by the pooled pre-test
standard deviation (SD) (1). A percentage change from pre-
test to post-test was also calculated. A small sample bias
adjustment was applied to each ES (Morris, 2008). The var-
iance around each ES was calculated using the sample size in
each study and mean ES across all studies (Borenstein,
Hedges, & Higgins, 2009).
2B. J. SCHOENFELD ET AL.
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Statistical analyses
Meta-analyses were performed using robust variance meta-
regression for multi-level data structures, with adjustments
for small samples (Hedges, Tipton, & Johnson, 2010; Tipton,
2015). Study was used as the clustering variable to account for
correlated effects within studies. Observations were weighted
by the inverse of the sampling variance. Model parameters
were estimated by the method of restricted maximum like-
lihood (REML) (Thompson & Sharp, 1999); an exception was
during the model reduction process, in which parameters
were estimated by the method of maximum likelihood, as
likelihood ratio tests cannot be used to compare nested mod-
els with REML estimates. Separate meta-regressions on ESs
were performed with the following moderator variables: total
sets per muscle group per week as a continuous variable; total
sets per muscle group per week categorised as low (<5),
medium (5–9) or high (10+); total sets per muscle group per
week categorised as lower (<9) or higher (9+) and total sets
per muscle group per week categorised as lower or higher
based on the comparison group within each study. For the
latter, if a study had 3 comparison groups, the highest volume
group was classified as “Higher”, and the two lower volume
(LV) groups were classified as “Lower”. In the latter regression
model, mean differences in ES were calculated for each study
to give a study-level ES for the difference between HV and LV
and to allow the generation of a forest plot. To assess the
practical significance of the outcomes, the equivalent per cent
change was calculated for each meta-regression outcome. To
assess the potential confounding effects of study-level mod-
erators on outcomes, an additional full meta-regression model
was created with the following predictors: total sets per mus-
cle group per week (continuous variable), gender (male,
female or mixed), age category (younger or older), weeks,
hypertrophy measurement type (direct or indirect) and body
portion (upper, lower or whole). The model was then reduced
by removing predictors one at a time, starting with the most
insignificant predictor (Burnham & Anderson, 2002). The final
model represented the reduced model with the lowest
Bayesian Information Criterion (Schwarz, 1978) and that was
not significantly different (P>0.05) from the full model when
compared using a likelihood ratio test. Weekly set volume was
not removed during the model-reduction process. Since all
covariates were removed during the model-reduction process,
and the simple model with set volume as the lone covariate
was not significantly different from the full model, only the
results of the simple models are reported. To explore possible
interactions between set volumes and other variables, sepa-
rate regressions were performed on set volume and its inter-
action with age category, gender category, body half and
measurement type.
In order to identify the presence of highly influential stu-
dies which might bias the analysis, a sensitivity analysis was
carried out for each model by removing one study at a time,
and then examining the set volume predictor. Studies were
identified as influential if removal resulted in a change of the
Records identified through
database searching
(n = 1474)
Screening
Included Eligibility Identification
Additional records identified
through other sources
(n = 2)
Total records screened
(n = 1476)
Full-text articles assessed
for eligibility
(n = 38)
Full-text articles excluded,
with reasons
(n = 21)
Studies included in
meta-analysis
(n = 17)
Studies included in
meta-analysis
(n = 15)
Additional articles
excluded, with reasons
(n = 2)
Figure 1. Flow diagram of search process.
JOURNAL OF SPORTS SCIENCES 3
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Table 1. Summary of hypertrophy training studies investigating volume.
Study ParticipantsDesign Study duration
Weekly sets
per exercise Hypertrophy measurement Findings
Bottaro et al.
(2011)
30 untrained
young men
Random assignment to a resistance training protocol
where one group performed 3 sets of knee extension
exercise and 1 set of elbow flexion exercise while the
other group performed 3 sets of elbow flexion exercise
and 1 set of knee extension exercise. All participants
performed 8–12RM of each exercise twice per week.
12 weeks High: 6
Low: 2
Ultrasound No significant differences in muscle
thickness between conditions (Elbow
flexors: 5.9% for high, 7.2% for low;
Quads: 2.5% for high, −2.9% for low)
Cannon and
Marino (2010)
31 untrained
young and
elderly women
Random assignment to a resistance-training protocol
performed either 1 or 3 sets per exercise. Training
consisted of knee extension and knee flexion exercise
performed 3 days a week at an intensity of 75% 1RM.
10 weeks High: 9
Low: 3
MRI No significant differences in muscle
volume between conditions (10.7%
for high, 6.0% for low)
Correa et al.
(2015)
36 untrained
postmenopausal
women
Random assignment to a resistance-training protocol
performed either 1 or 3 sets per exercise. All
participants performed 8 exercises targeting entire
body at 15RM. Training was carried out 3 days a week
for 11 weeks.
11 weeks High: 9
Low: 3
Ultrasound Significantly greater increases in muscle
thickness of the quadriceps for the
high volume condition (20.4% for
high; 11.6% for low)
Galvao and Taaffe
(2005)
28 untrained
elderly men and
women
Random assignment to a resistance-training protocol
performed either 1 or 3 sets per exercise. All
participants performed seven exercises (chest press,
seated row, triceps extension, biceps curl, leg press, leg
curl, leg extension) targeting the entire body at 8RM.
Training was carried out twice weekly.
20 weeks High:9
Low:~5
DXA No significant differences in lean body
mass between conditions (1.5% for
high, 1.0% for low)
McBride et al.
(2003)
28 young
untrained men
and women
Random assignment to a resistance-training protocol
consisting of 5 different exercises including the biceps
curl, leg press, chest flye, sit-up and back extension.
One group performed a single set of each of these
exercises while the other group performed 6 sets for
the biceps curl and leg press and 3 sets for all other
exercises. All participants performed 6-15RM of the
exercises twice weekly.
12 weeks High: 12
Low: 2
DXA No significant differences in lean body
mass between conditions (Upper
body: 0% for high, 0% for low; Lower
body: 5.1% for high, 0% for low)
Mitchell et al.
(2012)
18 untrained
young men
Within-participant design where participants trained one
leg with 3 sets and the other with 1 set at 80% 1RM on
a knee extension machine. Training was carried out 3
days-per-week.
10 weeks High: 9
Low: 3
MRI and biopsy No significant differences in cross
sectional area between groups (MRI:
6.8% for high; 3.1% for low; Biopsy:
15.9% for high, 16.4% for low)
Ostrowski et al.
(1997)
27 resistance-
trained young
men
Random assignment to a resistance-training protocol
performed either 1, 2 or 4 sets per exercise. All
participants performed a 4-day split body routine
working each of the major muscle groups with
multiple exercises in a session at 7-12RM.
10 weeks High: 12–28
Med: 6–14
Low:3–7
Ultrasound No significant differences in muscle
thickness between conditions (Triceps:
4.8% for high, 4.7% for medium, 2.3%
for low; Quads: 12.3% for high, 4.6%
for medium, 6.3% for low)
(Continued )
4B. J. SCHOENFELD ET AL.
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Table 1. (Continued).
Study ParticipantsDesign Study duration
Weekly sets
per exercise Hypertrophy measurement Findings
Radaelli, Fleck,
et al. (2014)
48 young,
recreationally
trained men
Random assignment to a resistance-training protocol
performed either 1, 3 or 5 sets per exercise. All
participants performed 8-12RM for multiple exercises
for the entire body (bench press, leg press, lat
pulldown, leg extension, SP, leg curl, biceps curl,
abdominal crunch and triceps extension). Training was
carried out 3 days per week.
6 months High: 30
Med: 18
Low: 6
Ultrasound Significantly greater increases in elbow
flexor muscle thickness for the 5-set
condition compared to the other 2
conditions. Only the 3- and 5-SETS
groups significantly increased elbow
flexor muscle thickness from baseline.
Significantly greater increases in
elbow extensor muscle thickness in
the 5-set condition compared with
the other 2 conditions. Only the 5 set
group significantly increased triceps
extensor thickness from baseline.
(Biceps: 17.0% for high, 7.8% for
medium, 1.4% for low; Triceps: 20.8%
for high, 1.7% for medium, 0.5% for
low)
Radaelli, Wilhelm,
et al. (2014)
27 untrained
elderly women
Random assignment to a resistance-training protocol
performed either 1 or 3 sets per exercise. All
participants performed 10 exercises targeting the
entire body at 10-20RM (bilateral leg press, unilateral
elbow flexion, bilateral knee extension, lat pull-down,
bilateral leg curl, triceps extension, bench press, hip
abduction and adduction and abdominal crunch).
Training was carried out twice weekly.
6 weeks High: 12
Low:4
Ultrasound No significant differences in muscle
thickness between conditions (6.7%
for high, 4.4% for low)
Radaelli, Botton,
et al. (2014)
20 untrained
elderly women
Random assignment to a resistance-training protocol
performed either 1 or 3 sets per exercise. All
participants performed 10 exercises targeting the
entire body at 6-20RM (bilateral leg press, unilateral
elbow flexion, bilateral knee extension, lat pull-down,
bilateral leg curl, triceps extension, bench press, hip
abduction and adduction and abdominal crunch).
Training was carried out twice weekly.
20 weeks High: 12
Low:4
Ultrasound Significantly greater increases in
quadriceps muscle thickness for the
high-volume group (Biceps: 14.5% for
high, 18.8% for low; Quads: 17.1% for
high, 11.9% for low)
Rhea et al. (2002) 18 resistance-
trained young
men
Random assignment to a resistance-training protocol
performed either 1 or 3 sets-per-exercise. All
participants performed 4-10RM on the bench press
and leg press. Participants also performed an
additional set of multiple exercises considered
unrelated to the bench press or leg press (biceps curl,
lat pull-down, abdominal crunches, back extensions
and seated rows). Training was carried out 3 days-per-
week.
12 weeks High: ~5
Low: 3
BodPod No significant differences in lean body
mass between conditions (1.7% for
high, 1.1% for low)
Ribeiro et al.
(2015)
30 untrained
elderly women
Random assignment to a resistance-training protocol
consisting of 8 exercises for the total body (chest press,
horizontal leg press, seated row, knee extension,
preacher curl, leg curl, triceps pushdown and seated
calf raise) performed either 1 or 3 days-per-week. All
participants performed 10–15 repetitions for 3 days-
per-week.
12 weeks High: ~10
Low: ~4
DXA No significant differences in lean body
mass between conditions (1.6% for
high, 1.1% for low)
(Continued )
JOURNAL OF SPORTS SCIENCES 5
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Table 1. (Continued).
Study ParticipantsDesign Study duration
Weekly sets
per exercise Hypertrophy measurement Findings
Rønnestad et al.
(2007)
21 untrained
young men
Random assignment to a resistance-training protocol
where one group performed 3 sets of upper body
exercise and 1 set of lower body exercise while the
other group performed 3 sets of lower body exercise
and 1 set of upper body exercise. Training consisted of
8 exercises for the entire body (leg press, leg
extension, leg curl, seated chest press, seated rowing,
latissimus pull-down, biceps curl and shoulder press)
performed at 7-10RM and carried out 3 days-per-week.
11 weeks High: 9–18
Low: 3–6
MRI Significantly greater increases in thigh
muscle CSA for the HV condition
(Trapezius: 14.3% for high, 9.8% for
low; Quads: 12.0% for high, 8.0% for
low; Hamstrings: 10.1% for high, 6.0%
for low)
Sooneste et al.
(2013)
8 untrained young
men
Within-participant crossover where all participants
performed a two day-per-week resistance-training
protocol of preacher curls so that one arm used 3 sets
in a session and the other arm used a single set in the
following session. Training was performed at 80% 1RM
and carried out 2 days-per-week.
12 weeks High: 6
Low: 2
MRI Significantly greater increases in upper
arm CSA for the high-volume
condition (15.9% for high, 2.8% for
low)
Starkey et al.
(1996)
48 untrained
mixed-aged
men and
women
Random assignment to a resistance-training protocol of
knee flexion and extension performed either 1 or 3
days-per-week. All participants performed 8-12
repetitions for 3 days-per-week.
14 weeks High: 9
Low: 3
Ultrasound No significant differences in muscle
thickness of the anterior or posterior
thigh muscles between conditions,
although only the high-volume group
significantly increased hypertrophy of
the vastus medialis relative to control
(2.9% for high, 2.5% for low).
Abbreviations: MRI (magnetic resonance imaging); DXA (dual energy X-ray absorptiometry); CSA (cross sectional area).
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predictor going from significant or a trend (P≤0.10) to non-
significant (P>0.10), or vice versa, or if removal caused a large
change in the magnitude of the coefficient.
All analyses were performed using package metaphor in R
version 3.2.3 (The R Foundation for Statistical Computing,
Vienna, Austria). Effects were considered significant at
P≤0.05, and trends were declared at 0.05 < P≤0.10. Data
are reported as x ± standard error of the means (SEM) and
95% confidence intervals (CIs).
Results
The final analysis comprised 34 treatment groups from 15
studies. The mean ES across all studies was 0.38 ± 0.08 (CI:
0.21, 0.56). The mean per cent change was 6.8 ± 1.3% (CI:
3.9, 9.7).
Weekly sets (continuous per muscle)
Outcomes for weekly sets as a continuous variable are shown
in Table 2. There was a significant effect of the number of
weekly sets on changes in muscle size (P=0.002). Each addi-
tional set per week was associated with an increase in ES of
0.023. This was equivalent to an increase in the percentage
gain by 0.37% for each additional weekly set.
Weekly sets (lower versus higher within studies per
muscle)
Outcomes for weekly sets categorised as lower or higher
within each study are shown in the forest plot in Figure 2.
There was a significant effect of volume (P=0.03); the ES
difference between HV and LV was 0.241 ± 0.101 (CI: 0.026,
0.457). This was equivalent to a difference in percentage gain
of 3.9%.
Weekly sets (<5, 5–9 and 10+ per muscle)
Outcomes for weekly sets as a three-level categorical variable
are shown in Table 2. There was a trend for an effect of weekly
sets (P=0.074). Mean ES for each category were 0.307 for <5
sets, 0.378 for 5–9 sets and 0.520 for 10+ sets. This was
equivalent to percentage gains of 5.4%, 6.6% and 9.8%,
respectively.
Weekly sets (<9, 9+ per muscle)
Outcomes for weekly sets as a two-level categorical variable
are shown in Table 2. There was a trend for an effect of weekly
sets (P=0.076). Mean ES was 0.320 for <9 sets, and 0.457 for 9
+ sets. This was equivalent to percentage gains of 5.8% and
8.2%, respectively.
Interactions
There was no significant interaction between weekly set
volume and gender (P=0.55), body half (P=0.28) or age
(P=0.66). There was a significant interaction with the type of
hypertrophy measurement (P=0.037). The mean increase in ES
for each additional weekly set was 0.023 for direct measure-
ments (CI: 0.009, 0.037), but only 0.006 for indirect measure-
ments, a value which was not significantly different from 0 (CI:
−0.023, 0.12). This was equivalent to an increase in the percen-
tage gain by 0.38% for each additional weekly set for direct
measurements (CI: 0.14, 0.62), but only 0.21% for each addi-
tional weekly set for indirect measurements (CI: −0.28, 0.52).
Sensitivity analysis
Sensitivity analysis revealed one influential study. Removal of
the study by Radaelli, Fleck, et al. (2014) reduced the impact of
the weekly number of sets on hypertrophy (Table 3). The
estimate for the change in ES for each additional set was
reduced to 0.013 (P=0.008). This was equivalent to an increase
in the percentage gain by 0.25 for each additional weekly set.
The study level ES in Figure 2, representing the within-study
difference between HV and LV, decreased to 0.147 (CI: 0.033,
0.261; P=0.016). This was equivalent to a difference in percen-
tage gain of 3.1%. In the 3-category model, there was no longer
an advantage to 10+ sets; mean ES for <5, 5–9 and 10+ sets
were 0.306, 0.410 and 0.404, respectively. This was equivalent to
percentage gains of 5.5%, 7.2% and 8.6%, respectively. In the
two-category model (<9 sets and 9+sets), there was no longer a
trend for an effect of weekly sets (P=0.12). Mean ES for <9 sets
and 9+ sets were 0.316 and 0.425, respectively. This was equiva-
lent to percentage gains of 5.9% and 8.0%, respectively.
Discussion
The present study sought to compare the effects of varying RT
volumes on established markers of muscle growth based on a
systematic analysis of pooled data from the current literature.
Results showed an incremental dose-response relationship
Table 2. Impact of weekly set volume on effect size and percentage change in
muscle size.
Weekly sets per
muscle group ES 95% CI P-value
Equivalent
percentage gain
Each additional
weekly set
0.023 ± 0.006 0.010, 0.036 0.002 0.37
<5 0.307 ± 0.07 0.152, 0.462 0.074 5.4
5–9 0.378 ± 0.13 0.092, 0.664 6.6
10+ 0.520 ± 0.13 0.226, 0.813 9.8
<9 0.320 ± 0.06 0.185, 0.455 0.076 5.8
9+ 0.457 ± 0.12 0.208, 0.707 8.2
Table 3. Impact of weekly set volume after removal of study by Radaelli, Fleck,
et al. (2014).
Weekly sets per
muscle group ES 95% CI P-value
Equivalent
percentage gain
Each additional
weekly set
0.013 ± 0.004 0.004, 0.021 0.008 0.25
<5 0.306 ± 0.08 0.137, 0.474 0.059 5.5
5–9 0.410 ± 0.13 0.099, 0.721 7.2
10+ 0.404 ± 0.09 0.217, 0.592 8.6
<9 0.316 ± 0.07 0.166, 0.466 0.12 5.9
9+ 0.425 ± 0.12 0.161, 0.689 8.0
JOURNAL OF SPORTS SCIENCES 7
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whereby progressively higher weekly training volumes
resulted in greater muscle hypertrophy. These findings were
seen across all predictor models employed as determined by
increasing ES as well as greater percentage gains in muscle
mass. Results are consistent with those of previous meta-
analytic work (Krieger, 2010), and expand on prior findings
with the inclusion of a substantial amount of new data using
more precise methods of measurement. These results also are
in agreement with acute research showing greater post-exer-
cise muscle protein synthesis (MPS) and intracellular anabolic
signalling for multiple versus single-set protocols (Burd et al.,
2010; Kumar et al., 2012; Mitchell et al., 2012; Terzis et al.,
2010)
A significant dose-response effect was seen when analysing
the number of weekly sets as a continuous predictor. Each
additional weekly set performed was associated with an
increase in ES of 0.02, equating to a 0.36% hypertrophic
gain. Sub-analysis of covariates revealed a significant interac-
tion between sets per week and the type of measurement,
making it very likely that these findings were not due to
chance alone (Hopkins, Marshall, Batterham, & Hanin, 2009).
The increase in ES for each additional weekly set was 0.02 for
direct muscle-specific measures (MRI and ultrasound), but only
0.01 for whole-body measures (DXA and BodPod). This under-
scores the importance of using direct measurements when
assessing hypertrophic outcomes, as they are more sensitive
to detecting subtle changes in muscle size (Levine et al., 2000).
Contrary to findings of Rønnestad et al. (2007), who reported a
dose-response effect for the lower- but not upper-body mus-
culature, meta-regression of included studies did not detect
any growth-related differences between body segments based
on RT volume (P=0.30). No other covariate including age,
gender or study duration was found to significantly affect
results.
Dose-response effects were noted when stratifying sets
into low (≤4 sets · week
–1
), medium (5–9 sets · week
–1
) and
high (≥10 sets · week
–1
) volumes. Although results did not
reach statistical significance, the low observed P-value (0.074)
indicates a good likelihood that results were not due to
chance alone (Hopkins et al., 2009). Null findings may be due
to reduced statistical power as a consequence of stratification
of the model. The ES displayed a graded volume-dependent
increase progressing from low to medium to high volume
conditions (0.30, 0.36 and 0.50, respectively). These values
were paralleled by graded increases in percentage muscle
growth (5.4%, 6.5% and 9.6%, respectively), indicating that
greater muscular development is achieved by performing at
least 10 weekly sets per muscle group.
When considering weekly sets as a binary predictor (<9 versus
≥9 sets · week
–1
), findings did not reach statistical significance
between conditions. However, when taking a magnitude-based
approach to statistical inference, the low observed P-value
(0.076) indicates a good likelihood that results were not due to
chance alone (Hopkins et al., 2009). Null findings may be due to
reduced statistical power as a consequence of stratification of
the model. Moreover, ES favoured HV compared to LV (0.66
versus 0.43, respectively), and these values mirrored percentage
gain increases in hypertrophy (8.0% versus 5.7%, respectively).
The paucity of data investigating weekly volumes of >12 sets
prevented analysis of very high training volumes on hyper-
trophic outcomes. Thus, it remains unclear as to where the
upper threshold lies as to the dose-response relationship
between RT volume and muscular growth.
Our analysis looked only at hypertrophy-related outcomes
and did not endeavour to ascertain underlying mechanisms
behind the dose-response relationship. Nevertheless, it can be
speculated that results are attributed at least in part to the
cumulative effects of time under tension at a given load.
Hypothetically, repeated within-session stimulation of muscle
tissue is necessary to drive intracellular signalling in a manner
that maximises the anabolic response to RT. Considering that
muscle hypertrophy is predicated on the dynamic balance
between MPS and breakdown (Sandri, 2008), higher RT
volumes would therefore conceivably sustain weekly anabo-
lism to a greater degree than LV. It also is feasible that
differences in metabolic stress between conditions may play
a role in results. Research indicates that exercise-induced
metabolic stress augments muscle protein accretion when a
minimum threshold for mechanical tension is achieved
(Schoenfeld, 2013). Given evidence that metabolite build-up
Figure 2. Forest plot of studies comparing the hypertrophic effects of different training volumes where the comparison made within each study analysed lower vs.
higher number of sets. The data shown are mean ±95% CI; the size of the plotted squares reflect the statistical weight of each study. Abbreviations: ES (effect size).
8B. J. SCHOENFELD ET AL.
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is significantly greater in multiple versus single set protocols
(Gotshalk et al., 1997), a rationale exists whereby this phenom-
enon enhances anabolism to a greater extent in high-volume
protocols.
A primary limitation of the current literature on the topic is
the lack of controlled research in resistance-trained individuals.
Only two studies to date investigated the effects of RT volume
on changes in muscle mass. Rhea et al. (2002) found no sig-
nificant differences in fat-free mass when training with 3 sets
versus 1 set in cohort of recreationally trained men (minimum
of 2 years RT experience working out at least 2 days · week
–1
).
The study was limited by the use of an indirect measurement
instrument (BodPod), that as shown in the present analysis, may
lack the sensitivity to detect subtle changes in lean mass.
Moreover, only the bench press and leg press were manipu-
lated for training volume, attenuating the potential dose-
response effects on whole-body muscle growth and thereby
making it difficult to draw practical conclusions. Ostrowski et al.
(1997) used B-mode ultrasound to investigate hypertrophic
changes in a cohort of resistance-trained young men (1–
4 years RT experience with the ability to bench press and
squat 100% and 130% of body mass, respectively) performing
either 3, 6 or 12 weekly sets per muscle group. Although no
significant effects were demonstrated between conditions, the
highest volume group displayed markedly greater absolute
increases in rectus femoris cross sectional area compared to
the medium and low volume conditions (13.1% versus 5% and
6.7%, respectively). Null findings may be the result of a type II
error given the small sample size employed. Clearly, more
studies are needed in resistance-trained individuals to be able
to draw research-based conclusions as to the effects of RT
volume on muscle growth.
Practical applications
The current body of evidence indicates a graded dose-
response relationship between RT volume and muscle growth.
Clearly, substantial hypertrophic gains can be made using low-
volume protocols (≤4 weekly sets per muscle group). Such an
approach therefore represents a viable muscle-building option
for those who are pressed for time or those to which the
conservation of energy is an ongoing concern (i.e., frail
elderly). However, the present analysis shows that HV proto-
cols produce significantly greater increases in muscle growth
than LV. Based on our findings, it would appear that perfor-
mance of at least 10 weekly sets per muscle group is necessary
to maximise increases in muscle mass. Although there is cer-
tainly a threshold for volume beyond which hypertrophic
adaptations plateau and perhaps even regress due to over-
training, current research is insufficient to determine the
upper limits of this dose-response relationship.
It is clear that the optimal RT dose will ultimately vary
between individuals, and these differences may have a genetic
component. For example, research shows that the variances in
the angiotensin converting enzyme (ACE) genotype affects the
strength-related response to single- versus multiple-set rou-
tines (Colakoglu et al., 2005). Although the ACE gene does not
appear to mediate the hypertrophic response to RT
(Charbonneau et al., 2008), it remains possible that other
genes may well influence volume-related muscular gains.
Consistent with an evidence-based approach, practitioners
should carefully monitor client progression and adjust training
dosages based on the individual’s response.
Disclosure statement
No potential conflict of interest was reported by the authors.
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