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Evidence-Based Resistance Training Recommendations for Muscular Hypertrophy

Authors:

Abstract

Objective: There is considerable interest in attaining muscular hypertrophy in recreational gym-goers, bodybuilders, older adults, and persons suffering from immunodeficiency conditions. Multiple review articles have suggested guidelines for the most efficacious training methods to obtain muscular hypertrophy. Unfortunately these included articles that inferred hypertrophy markers such as hormonal measurements, used older techniques that might not be valid (e.g. circumference) and failed to appropriately consider the complexity of training variables. Methods: The present commentary provides a narrative review of literature, summarising main areas of interest and providing evidence-based guidelines towards training for muscular hypertrophy. Conclusions: Evidence supports that persons should train to the highest intensity of effort, thus recruiting as many motor units and muscle fibres as possible, self-selecting a load and repetition range, and performing single sets for each exercise. No specific resistance type appears more advantageous than another, and persons should consider the inclusion of concentric, eccentric and isometric actions within their training regime, at a repetition duration that maintains muscular tension. Between set/exercise rest intervals appear not to affect hypertrophy, and in addition the evidence suggests that training through a limited range of motion might stimulate similar results to full range of motion exercise. The performance of concurrent endurance training appears not to negatively affect hypertrophy, and persons should be advised not to expect uniform muscle growth both along the belly of a muscle or for individual muscles within a group. Finally evidence suggests that short (~3 weeks) periods of detraining in trained persons does not incur significant muscular atrophy and might stimulate greater hypertrophy upon return to training. Key words: muscular size, bodybuilding, intensity, genetics, concurrent, endurance
Medicina Sportiva
Med Sport 17 (4): 217-235, 2013
DOI: 10.5604/17342260.1081302
Copyright © 2013 Medicina Sportiva
REVIEW ARTICLE
217
EVIDENCEBASED RESISTANCE TRAINING
RECOMMENDATIONS FOR MUSCULAR HYPERTROPHY
James Fisher1(A,B,D,E,F), James Steele1 (A,B,D,E,F), Dave Smith2(D,E,F)
1Southampton Solent University UK
2Manchester Metropolitan University, UK
Abstract
Objective: There is considerable interest in attaining muscular hypertrophy in recreational gym-goers, bodybuilders,
older adults, and persons suffering from immunodeficiency conditions. Multiple review articles have suggested guidelines
for the most efficacious training methods to obtain muscular hypertrophy. Unfortunately these included articles that inferred
hypertrophy markers such as hormonal measurements, used older techniques that might not be valid (e.g. circumference)
and failed to appropriately consider the complexity of training variables.
Methods: The present commentary provides a narrative review of literature, summarising main areas of interest and
providing evidence-based guidelines towards training for muscular hypertrophy.
Conclusions: Evidence supports that persons should train to the highest intensity of effort, thus recruiting as many
motor units and muscle fibres as possible, self-selecting a load and repetition range, and performing single sets for each
exercise. No specific resistance type appears more advantageous than another, and persons should consider the inclusion
of concentric, eccentric and isometric actions within their training regime, at a repetition duration that maintains muscular
tension. Between set/exercise rest intervals appear not to affect hypertrophy, and in addition the evidence suggests that
training through a limited range of motion might stimulate similar results to full range of motion exercise. The performance
of concurrent endurance training appears not to negatively affect hypertrophy, and persons should be advised not to expect
uniform muscle growth both along the belly of a muscle or for individual muscles within a group. Finally evidence suggests
that short (~3 weeks) periods of detraining in trained persons does not incur significant muscular atrophy and might stimulate
greater hypertrophy upon return to training.
Key words: muscular size, bodybuilding, intensity, genetics, concurrent, endurance
Introduction
Muscular growth and hypertrophy is of consider-
able interest to athletes and lay persons wishing to
increase their muscularity. As aresult there have been
multiple publications reviewing the mechanisms [1],
as well as providing guidelines and training recom-
mendations. [1-5]. The most recent of these papers [1]
includes meta-analytical studies [2,5], and associated
position stand publications [6], as well as the opinion
of authors via text-books [7] as evidence to support
their claims. Such areview should be considering only
original, empirical, peer-reviewed research articles.
The inclusion of studies measuring a hormonal re-
sponse, which only infers potential for hypertrophic
adaptations, is also cause for concern as discussed
herein. Many other publications [2,4,5] have received
criticism for alack of scientific rigour [e.g. 8-10] and
thus there appears need for amore scrupulous review.
The present piece is not aimed as acritique of previous
publications, but rather aims to discuss the research
and provide evidence-based recommendations for
muscular hypertrophy.
Symptomatic, Aging, and Special Populations
Sarcopenia (muscle wastage) and thus, muscle
hypertrophy, are of considerable interest for special
populations e.g. older adults [11-13], persons suf-
fering from immunodeficiency conditions [14,15],
and bodybuilders [16]. However, the present article
is concerned only with the hypertrophic adaptations
to resistance training for asymptomatic adults. Whilst
the nature of these more complex areas, specifically
bodybuilding, might seem unwise to dismiss, body-
builders, weightlifters and the like should be consid-
ered an elite population, likely with genetics that are
favourable to muscular growth, and potentially using
powerful supplementation [17] or anabolic steroids
[18], and/or growth hormones [19,20]. As a result
their training routines and growth are not considered
to be within expected ranges for the general popula-
tion. Indeed, older or symptomatic persons likely do
not respond to resistance training in the same way as
asymptomatic persons, therefore, the present article
has excluded research considering any specialised
population sample group.
Physiological Biomarkers
We can also consider the biomarkers linked to, or
assumed to mediate, hypertrophy and muscle remod-
elling. This includes but is not limited to: hormone
levels, e.g. IGF-1, testosterone, and growth hormone,
[21-23]; satellite cell activation, proliferation and dif-
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Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
ferentiation [23,24]; protein synthesis [26,27], and
genetic variation [28]. These markers are discussed
in detail in several articles (e.g. 1,29-31] and some
authors have made recommendations from these in-
ferred markers [1,4]. However, multiple publications
have provided extensive critical analysis of these hy-
potheses and the associated complexities [e.g. 32-36].
Whilst we recognise the importance of understand-
ing hypertrophic mechanisms, we suggest that these
physiological biomarkers only infer ahypertrophic
response. As such the present article does not discuss
the measurement of these variables or other mecha-
nisms, but rather is focused upon research examining
the manipulation of training techniques/variables and
their effects upon in vivo hypertrophic measurement.
Acute and Chronic Hypertrophy and Methods of
Measurement
Muscular hypertrophy can be defined as acute,
i.e. as aresult of sarcoplasmic hypertrophy [37-39],
or chronic, i.e. as aresult of an increased number of
sarcomeres and myofibrils [40-42]. It is important that
hypertrophy is measured using amethod that can dif-
ferentiate between acute changes and chronic adapta-
tion therefore the present study will consider research
using the most accurate techniques, such as magnetic
resonance imaging (MRI), computerised tomography
(CT) and ultrasound, all of which are well-validated
[43-45]. In measurement of hypertrophy several
studies have reported muscle CSA or muscle thick-
ness (MT) from asingle ‘slice’ measurement whilst
others have taken multiple measurements through
the length of amuscle and calculated and reported
avolume. Since in the present review we make no
attempt to compare statistical values between studies
using different techniques, CSA, MT and volume are
considered adequate reporting for muscle size and thus
hypertrophic changes. With these criteria defined, the
aim of the present article is to provide readers with
aseries of scientifically-validated recommendations
for resistance training for healthy, asymptomatic adults
looking to increase muscular hypertrophy.
Methods
Aliterature search was completed up to the end
of May 2013, using MEDLINE, SportDiscus and
Google Scholar databases. In addition, the reference
list of each article gathered was used to broaden the
literature search, as well as previous reviews [1-6,46-
53]. The previously detailed inclusion and exclusion
criteria were applied to groups within research studies
considering hypertrophy. In addition the exclusion of
groups performing any irregular forms of training, e.g.
hypoxic or occluded training1 was also applied. Articles
manipulating training supplementation as avariable
were also excluded.
Whilst review articles [2,3,5] have served to try to
compile all the statistical data from respective stud-
ies into single results, the present piece makes no
such attempt due to the complex individual methods
and disparity of reporting data between the studies.
Thus given the broad area of this review, anarrative
approach has been utilised, discussing the between
group differences of each study in their own merit,
and grouping similar studies in an attempt to provide
recommendations based on the evidence. Finally, it is
worth mentioning that several papers were excluded
from the present review due to unclear method-
ological manipulation of variables including: exercises
performed, volume (including sets and repetitions),
load, and repetition duration [55-59]. Such studies
should be commended for their attempt to provide
‘real-life’ training regimes but ultimately are limited
in any application due to the lack of detail/control of
variables [60].
Having applied the inclusion and exclusion criteria
the present piece presents results from 57 different
peer-reviewed journal articles in an attempt to provide
evidence-based resistance training recommendations
for hypertrophy. The following sub-sections have been
discussed and summarized:
• IntensityofEffort,LoadandRepetitionRange
• RepetitionDurationandRestIntervals
• VolumeandConcurrentResistanceandEndurance
Training
• RangeofMotion,ContractionTypesandResistance
Types
• Non-UniformMuscleGrowth,ContralateralEffects
and Training and Detraining Time Course
• TrainingStatusandGenetics
Intensity of Effort, Load and Repetition Range
Intensity
Intensity of effort has previously been considered
to be perhaps the single most influential control-
lable variable for enhancing muscular strength [61].
Evidence suggests that, through the size-principle, i.e.
the sequential recruitment of motor units [62], that
training to momentary muscular failure maximizes
enrolment of muscle fibres to catalyse adaptation.
Two studies have considered hypertrophic measure-
ments using electrical stimulation of muscle contrac-
tion [63,64]. Ruther, et al., [63] reported favourable
increases in hypertrophy as measured by MRI pre-
and post-intervention for atraining group receiving
electrical stimulation (10%) compared to agroup
performing voluntary muscle activation (4%). Whilst
both groups trained at maximal effort, this article
1 The long term health implications of hypoxic/occluded training have not been thoroughly tested, whilst the effects of cuff pressure and moderate/
complete occlusion have implications for muscle activation [54]
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Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
suggests that the diminished ability of untrained sub-
jects to recruit motor units limits their potential for
hypertrophy, and that recruiting agreater number of
muscle fibres (even through electrical stimulation)
increases hypertrophic gains. In support Gondin et
al. [64], reported significant increases in muscle CSA
for agroup of participants performing electrically
stimulated isometric knee extension exercises. The
stimulated contraction equated to approximately
68±13%ofmaximal voluntarycontraction(MVC),
whilst the training intervention lasted 8-weeks. This
suggests that regardless of the stimulus, it is the acti-
vation of motor units and muscle fibres that catalyses
hypertrophic increases.
Goto et al. [65] considered the effects of either
strength (S) or combination (C) regimes on muscu-
lar hypertrophy. Both groups performed an identical
workout for 6 weeks. However, from week 7 the pro-
tocol for the S group consisted of 5 sets at 90% 1RM
with 3-minutes rest between each set, whereas the C
group performed the same regime with an additional
sixth set performed 30 seconds after the fifth set us-
ing 50% 1RM. The authors commented that each set
was taken to muscular failure. Muscle CSA of the
mid-thigh revealed no significant differences between
groups S and C at both week 6 and week 10 suggesting
that when training to failure there appears no differ-
ence in load or repetitions used. However, the authors
commented that that there was agreater hypertrophy
for the C group which approached significance (P =
0.08). Due to the nature of the decreased rest interval
before the final set within the C group, this might pro-
vide evidence for the use of drop-sets, or break-down
sets, e.g. where muscular force is no longer sufficient
to lift aload the load is reduced and repetitions are
almost immediately continued. Future research should
consider hypertrophic changes as aresult of advanced
techniques such as drop-sets, and pre-exhaustion,
amongst others.
Whilst between-set rest periods will be discussed
in alater section, astudy by Goto et al. [66] considered
the effect of awithin-set rest period on muscular hy-
pertrophy of the quadriceps. Participants were divided
into three groups: no rest (NR), with rest (WR) and
control (CTR). Each training group performed 3 sets
of 10RM for lat pull-down and shoulder press, and
5 sets of 10RM for bilateral knee extension. The NR
group were permitted 1 minutes’ rest between sets and
exercises, whereas the WR group were instructed to
take an additional 30 seconds of rest midway through
each set (e.g. between the 5th and 6th repetitions). The
increases in muscle CSA of the thigh was significantly
greater in NR compared to WR groups (12.9 ±1.3 %
vs. 4.0 ±1.2% respectively). This suggests that the con-
tinuous and sequential recruitment of muscle fibres for
the NR group enhanced hypertrophy, whilst the rest
in the WR group allowed some motor units recovery
time preventing the need for recruitment of higher
threshold motor-units.
Load and Repetition Range
In association with the discussion of intensity of
effort, we should consider how the load lifted (%1RM)
or the number of repetitions performed affects mus-
cular hypertrophy. For example Hisaeda et al. [67]
considered two different resistance training protocols
described as being typical for strength (S; high load,
low repetition) and hypertrophy (H; low load, high
repetition). Participants trained 3 x / week for 8 weeks
using an isotonic knee extension exercise. Group H
performed 5-6 sets of 15-20RM with 90 seconds inter-
val between sets, whilst group S performed 8-9 sets of
4-5RM with ‘sufficient’ rest between each set. Pre- to
post-test results revealed asignificant increase in CSA
for the quadriceps femoris for both groups with no
significant difference between training interventions.
Reporting similar results, Kraemer et al. [68], consid-
ered the effect of multiple resistance training protocols
on hypertrophy in physically active, but untrained
women. Participants were divided into either total- or
upper-body training programs, and further divided
in to two groups; one using heavier load and lower
repetition range (starting at 8RM and progressing to
3RM) and the other using alighter load and higher
repetition range (starting at 12RM and progressing to
8RM). Muscle CSA was measured for the mid-thigh
and upper arm of the dominant limbs at weeks 0, 12
and 24 using MRI. All training groups showed asig-
nificant increase in upper arm CSA from weeks 0 to 12,
with no significant difference between groups. In ad-
dition all training groups showed afurther significant
increase in CSA of the upper arm from weeks 12 to 24,
once again with no significant difference between the
groups. Mid-thigh CSA showed asignificant increase
from weeks 0 to 12, and 12 to 24 in the whole body
training groups only, with no significant difference
between the groups.
Additional support comes from Popov et al. [69],
and Tanimoto et al., [70,71], who considered the
effects of low and high load training on muscular
hypertrophy. Each of these studies compared groups
training at ~50% 1RM to ~80% 1RM. All groups
trained to repetition maximum (RM), and results of
MRI showed no significant differences in hypertro-
phy between the groups. Ogasawara et al., [72] also
compared low- (30% 1RM) and high-load (75% 1RM)
resistance training, using the same participants with
a12 month detraining period between each 6-week
intervention. Participants trained to volitional fatigue
in the bench press exercise and post-intervention MRI
results revealed similar increases in pectoralis major
and triceps brachii cross sectional area with no sig-
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Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
nificant differences between groups. In addition Léger
et al., [73] considered groups training with high load
and low reps (3-5RM), and low load and high reps (20-
28RM). Following an 8-week intervention of leg press,
squat and leg extension training MRI revealed ~10%
increases in cross sectional area of the quadriceps in
both groups with no significant differences between
high- and low-repetition groups.
Finally an article that is discussed in greater detail
in alater section [74] considered rest intervals be-
tween sets. In this study the group with adecreasing
rest interval performed fewer repetitions, and also
used alighter load as aresult of decreased rest. This
amounted to asignificantly (P < 0.05) lower total
training volume throughout the 8-week intervention.
However, both the continuous interval and decreasing
interval groups showed significant hypertrophy mea-
sured by MRI with no significant difference between
the groups.
Summary
The evidence presented supports previous research
suggesting that it is the activation of muscle fibres
that appears to stimulate muscular responses [61,62]
causing hypertrophy. Thus, recruiting as many mo-
tor units as possible through training to momentary
muscular failure appears optimal for muscular hyper-
trophy. From the research discussed there appears no
substantiation of the claim that training using either
light or heavy loads is better for attaining hypertrophic
adaptations when training to MMF.
Repetition Duration & Rest Intervals
Repetition Duration
The area of repetition duration2 and use of explo-
sive lifting has been equivocal with regard to strength
gains, although previous recommendations have
suggested avelocity that maintains muscular tension
throughout the range of movement [61,75]. This sec-
tion will consider the research regarding repetition
duration and hypertrophic gain. Young and Bibby
[78] considered fast and slow training groups for ahalf
squat exercise. The fast group performed acontrolled
eccentric phase followed by an explosive concentric
phase, and the slow group performed both concentric
and eccentric phases in aslow and controlled manner’.
Muscle thickness (MT) of the mid-thigh was measured
using ultrasound, where results revealed significant
hypertrophy in both fast and slow groups with no sig-
nificant differences between these groups. In addition,
the aforementioned studies by Tanimoto et al. [70,71]
considered the effects of repetition duration and load
using aknee extension exercise, on quadriceps hyper-
trophy. Participants in the first study [70] were divided
in to three groups: low-load and high repetition dura-
tion (LST; 3 seconds concentric: 3 seconds eccentric
with 1 second pause and no relaxation phase at ~50%
1RM), high-load and normal repetition duration (HN;
1 second concentric: 1 second eccentric and 1 second
for relaxing with ~80% 1RM0 and low-load and nor-
mal repetition duration (LN; 1 second concentric: 1
second eccentric and 1 second for relaxing with ~50%
1RM)3. The second study did not include aLN group
but did utilise acontrol group. The authors state that
exercise intensity was determined at 8RM. In the first
study [70] muscle CSA of the quadriceps was measured
using MRI and in the second study MT was measured
using ultrasound. The LST and HN groups reported
significantly greater hypertrophy than the LN group in
the first study [70] and the control group in the second
study [71] with no significant difference between LST
and HN in either study [70,71]. We might consider that
if either increased repetition duration or an increased
load caused participants to reach MMF around 8RM,
as to how the LN group using both alighter load and
lower repetition duration also reached MMF at around
8RM. It seems more logical that the LN group did not
perform repetitions to MMF, which might be acause
for their lack of hypertrophic gains compared to LST
and HN.
The evidence appears to suggest that repetition
duration makes no significant difference to hypertro-
phic gain. However, we might further consider astudy
by Friedmann et al. [79] whose protocol required
control participants perform 25 repetitions with 30%
1RM within 45 seconds. Following 6 sets of 3 x / week
training cross sectional area results using MRI revealed
no significant increases in strength or hypertrophy.
Previous reviews have suggested that muscular tension
appears necessary to actively recruit muscle fibres to
cause increases in strength [e.g. 61,75], therefore we
can consider that explosive training of 25 repetitions
in 45 seconds (e.g. <1 second per concentric/eccentric
muscle action), with aload of 30% 1RM does not pro-
vide sufficient stimulus for strength or hypertrophic
gains. Thus, whilst repetition duration appears to have
no significant effect on hypertrophy, it appears that
muscular tension is arequirement. In support, alatter
study by the same authors [80] considering eccentric
overload (see later section on contraction types for
more details) used the same research design of 25 leg
extension repetitions in 45 seconds. Once again none
2 Repetition duration makes reference to the time taken to perform concentric and eccentric phases (CON: ECC) of asingle repetition. Previous re-
search has clarified the importance of the term repetition duration as opposed to velocity or speed, which makes reference to distance and time [76,77].
3 The authors incorrectly cite the groups as low or high intensity, where in fact they make reference to load (kg). Since all groups were training to RM we
suggest that all groups trained at the same intensity of effort but rather differed in load. In addition the authors make reference to slow or normal speed
where they did not cite aspeed but rather repetition duration (see previous footnote).
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Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
of the training groups reported any significant increase
in hypertrophy. Interestingly, the authors state that
multiple participants dropped out of the study citing
muscle soreness or injury. Later within the present re-
view we will discuss time-course of hypertrophy where
evidence has shown chronic adaptation in as short
as 3 weeks of resistance training [81,82]. However,
we must also recognise that not all participants will
respond in the same time-scale, therefore the 4-week
interventions by Friedmann et al. [79,80] simply might
not have been of sufficient duration.
Rest Intervals
The American College of Sports Medicine (ACSM)
[4] discussed rest intervals between sets and exercises,
suggesting that both short (30 second) and long (90
second) rest intervals are equally efficacious. Two stud-
ies [74,83] directly examining the effects of different
between set rest intervals have supported the idea that
these have little effect upon hypertrophy. Ahtiainen
et al. [83] compared the effects of between-set rest
intervals on muscle hypertrophy of the quadriceps
whilst controlling for total volume (alower load and
additional sets was used during ashort-rest protocol
to create asimilarity in total volume - load x sets x
repetitions - between the protocols). Their 6-month
intervention consisted of acrossover design where two
training groups completed ashort-rest (SR; 2 minutes)
and along-rest (LR; 5 minutes) 3-month intervention.
Muscle volume of the quadriceps was measured using
MRI, and results revealed that neither the 3-month
SR or LR group alone produced significant increases.
However, after the 6-month intervention (including
both LR and SR) both groups 1 and 2, showed signifi-
cant increases in muscle volume.
De Souza et al. [74] considered the effects of
between set rest intervals on muscular hypertrophy
without controlling for total volume. Participants
were randomly assigned to either continuous inter-
val (CI) or decreasing interval (DI). After 2-weeks of
standardized training the CI group continued to have
2-minute rest intervals where the DI group reduced
their between set/exercise rest interval as follows;
weeks 3, 4, 5, 6, 7, and 8 accommodated 105, 90, 75,
60, 45, and 30 seconds of rest, respectively. As aresult
of this decreased rest interval the load lifted and thus
total training volume (load x sets x repetitions) for
the DI group also decreased. The authors reported
statistically significant differences for the free-weight
back squat (CI=27,248.2 ±293.8kg vs. DI=23,453.6
±299.4kg) and free-weight bench press (CI=21,257.9
±172.7kg vs. DI=19,250.4 ±343.8kg). Interestingly
this additional rest and training load did not enhance
pre- to post-test 1RM strength for the squat or bench
press to any greater degree in the CI group than for
the DI group. Muscle CSA of the right thigh and
upper arm revealed significant hypertrophy pre- to
post-intervention in both groups with no significant
between-group differences.
Overall, it appears that although rest intervals
can have an acute impact upon total training volume
this bears little effect upon hypertrophic adaptation.
Additionally, different rest intervals appear to bear
little effect independently where volume has been
controlled between groups.
Summary
From the evidence presented it appears that mus-
cular tension is anecessity in stimulating hypertrophic
gains. Whilst studies considering high and low rep-
etition duration generally have found no significant
difference, we can conclude that it is the sequential re-
cruitment of muscle fibres and training to momentary
muscular failure that stimulates hypertrophic response
rather than the load being lifted or repetition duration
used. In addition the evidence suggests that whilst rest
interval appears to play arole in acute performance
e.g. both the repetitions performed and load lifted, it
did not affect the chronic strength or hypertrophic
gains acquired.
Other studies have considered repetition duration
and shall be discussed herein where appropriate to
their other independent variables (e.g. concentric vs.
eccentric muscle actions); however, we caution the
interpretation of those studies with regard to repetition
duration due to the use of isokinetic dynamometry.
See later for amore thorough discussion.
Volume and Concurrent Resistance and Endurance
Training
Volume
Arecent meta-analysis suggested that significantly
greater gains in hypertrophy can be obtained by the
performance of multiple sets of exercise compared
to single sets [5]. However, acritique of that meta-
analysis suggested that the disparity between studies,
as well as inclusion of studies which did not meet
inclusion/exclusion criteria, prevented such asimple
conclusion [10]. With this in mind it is prudent that the
present review consider the area of volume of training
for muscular hypertrophy.
Starkey et al. [84] divided 39 (19 males, 20 females)
healthy untrained participants in to either 1 set, 3 set or
control groups for bilateral knee extension and flexion
exercises. Ultrasound measures of muscle thickness
revealed significant hypertrophy pre- to post-test for
the quadriceps muscles; medialis (3 set) and lateralis
(1 set). In addition muscle thickness increased in the
hamstrings muscles from pre- to post-test, measured
at 40% and 60% from greater trochanter to lateral
epicondyle of the tibia, for both 1 set and 3 sets groups
with no significant difference between the groups.
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Ostrowski et al. [85] also considered volume, divid-
ing 35 trained males into 1 of 3 groups (1 set, 2 sets,
and 4 sets, of each exercise). This equated to 3, 6, or
12 sets of exercise per muscle group, performed for
4 different workouts each week; (i) legs, (ii) chest
and shoulders, (iii) back and calves and (iv) biceps
and triceps. Ultrasound was used to measure cross-
sectional area for the rectus femoris (RF) and muscle
thickness for the triceps brachii (TB). After 10 weeks of
resistance training ultrasound measurements revealed
significant increases in cross-sectional area for RF and
muscle thickness for TB within all the groups, but no
significant differences in the gains between the groups.
Since this study utilizes asplit routine of training dif-
ferent body parts on different days it likely replicates
what many gym goers looking to increase muscle mass
might perform. Thus the absence of significant differ-
ences between 1, 2, and 4 set training groups represents
an important finding. Afinal study considering the
lower body is that of Bottaro et al. [86] who compared
3 sets of knee extension and 1 set of elbow flexion
(3K-1E) to 1 set of knee extension and 3 sets of elbow
flexion (1K-3E). Muscle thickness was measured using
ultrasound pre- and post- intervention, and results
revealed significant increases in muscle thickness in
the elbow flexors in both groups with no significant
difference between groups. However, the authors also
reported no significant increases in muscle thickness
for the knee extensors in either group from pre- to
post- intervention.
Sooneste et al. [87] considered volume of train-
ing in acrossover designed study, comparing 1 and 3
sets of seated dumbbell preacher curl over a12 week
period. Each participant trained 2 x / week, perform-
ing 1 set of biceps curl on one arm, and 3 sets on the
other arm. Each set was performed at 80% 1RM for
10 repetitions or to muscular failure. Cross sectional
area was measured using MRI pre- and post- 1RM test-
ing. The authors reported astatistical significance in
hypertrophy over the 12 week period for both groups
(1 set; 8.0 ±3.7%, 3 set; 13.3 ±3.6%), with astatistically
significant between group increase in favour of the 3
set training intervention.
The studies presented herein appear to be conflict-
ing, with some research supporting multiple set train-
ing [87] whilst others suggest no significant difference
in hypertrophic gains between single and multiple sets
[84-86]. Perhaps asignificant consideration might be
that of total training volume; i.e. the number of sets
that activate an intended muscle group as opposed to
the number of sets of aspecific exercise. For example
Gentil et al. [88] considered the addition of single joint
(SJ) exercises to amulti-joint (MJ) resistance training
program. Participants were divided into MJ or MJ+SJ
groups in which they performed either bench press
and lat pull-down exercises (MJ), or bench press, lat
pull-down, triceps extension and elbow flexion exer-
cises (MJ+SJ) for 3 sets of 8-12 repetitions, 2 x / week
for 10 weeks. All sets were performed to concentric
failure. The authors comment “Because the purpose of
the study was to evaluate the effects of adding supple-
mental SJ exercises to aMJ exercise program, total train-
ing volume between the two groups was not equated.
Muscle thickness of the elbow flexors was measured
using ultrasound revealing significant increases in
hypertrophy for both MJ and MJ+SJ groups (6.46%
and 7.04%, respectively) with no significant differ-
ence between groups. Thus, the addition of an isolated
elbow flexion exercise to atraining program which
already incorporated the use of the elbow flexors in
alat pull-down exercise made no significance to the
increases in hypertrophy of said muscles. It would be
interesting for researchers in the future to compare the
effects of multiple sets of the same exercise with single
sets of different exercises.
Concurrent Resistance and Endurance Training
The completion of multiple exercises for similar
muscle groups should not solely refer to the use of
typical resistance exercises. Many traditional endur-
ance exercise modalities use the same muscles as
resistance training exercises. Thus, when considering
exercise volume we should also consider concurrent
resistance and conventional cardiovascular training.
McCarthy et al. [89] compared the hypertrophic ef-
fects of performing strength (S), endurance (E) and
concurrent strength and endurance (SE) exercise.
The S group performed 8-weight training exercises
for 3 sets of each for 5-7RM. The E group performed
50 minutes of continuous cycling at 70% maximum
heart rate. The SE training group performed both
training protocols in their entirety each training day
(with alternating order) with 10 to 20 minutes of rest
between each session. Muscle CSA of the knee exten-
sors and knee flexors/adductors was measured using
CT scan pre- and post- intervention. Results showed
significant hypertrophy for the knee extensors in all
groups, with significantly greater increases in S and SE
compared to E groups. In addition, significant hyper-
trophy was reported in the knee flexors/adductors in
both the S and SE groups, with no significant between
group differences.
Izquiredo et al. [90] also compared the hyper-
trophic effects of strength (S), endurance (E), and
strength and endurance (SE) training. Groups trained
2 x / week performing either 2 x strength (S), 2 x en-
durance (E), or 1 x strength and 1 x endurance (SE)
workouts, for 16 weeks on non-consecutive days. The
authors noted that the training programs used in this
study were similar to those reported previously [91].
These are both complex and vague, including unquan-
tified ranges (e.g. 10-15 repetitions, 3-5sets, 50-70%
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1RM) as well as failing to clarify whether exercise was
taken to muscular failure, and the inclusion of ‘and/
or’ when describing the exercises performed suggested
alack of parity between participants/groups. The en-
durance element consisted of aprogressive cycle task
at aconstant 60rpm for 30-40 minutes per session,
increasing in wattage based on individual blood lactate
profiles. All groups showed significant hypertrophy in
the quadriceps with no significant difference between
groups. The S group significantly increased biceps bra-
chii CSA where no significant increases were reported
for SE and E groups. Whilst this article suggests that
afrequency of 1 x / week is not sufficient to stimulate
hypertrophy in the elbow flexors, we raise concern
about the publication of vague (and consequently
impossible to duplicate) training regimes.
Finally Lundberg et al. [92] considered the effects
of resistance exercise and aerobic exercise versus just
resistance exercise upon hypertrophy of the knee
extensors. Each participant performed unilateral leg
extension resistance exercise on aflywheel4 ergometer
2 x / week for weeks 1, 3 and 5, and 3 x / week for weeks
2 and 4 for both limbs. In addition they performed
aerobic exercise on aunilateral cycle ergometer 3 x
/ week for one of the lower body limbs, consisting of
40 minutes continuous cycling at 70% of max wattage
(WMax) at acadence of 60 rpm. After 40 minutes the
workload was increased by ~20W and subjects were
encouraged to cycle until failure, which occurred
within 1-5 minutes. Thus, one leg belonging to each
participant performed aerobic exercise and resistance
training (AE+RT) or resistance training only (RT).
The results reported significant increases within and
between legs in quadriceps volume for AE+RT, and
RT only (13.6% and 7.8%, respectively). The authors
reported aconsistent response across all 10 subjects.
Whilst the present article is primarily concerned with
resistance training recommendations to increase
muscular hypertrophy, Lundberg et al.s [92] find-
ings suggest that preceding exhaustive AE for the
quadriceps might further enhance hypertrophy above
that of RT alone. Notably participants performing
AE were encouraged to cycle until failure as aresult
of increased resistance, which supports previous
evidence that training to muscular failure appears to
maximally stimulate muscle fibres for hypertrophic
response. Future research might consider this with
regard to kayaking, rowing or arm cranking tasks for
the upper body.
Summary
The research considered within the present section
suggests that volume of training (e.g. the number of
sets performed) does not show arelationship to hy-
pertrophic gains. Based on the present evidence dis-
cussed and the likelihood that most persons perform
multiple exercises that activate the same muscle group,
our recommendations are to perform asingle set of
each exercise to MMF. In addition, the research has
supported that persons wishing to include endurance
exercise in their training regime can do so without
negatively affecting their hypertrophic gains. Further
research should consider this area with regard to fre-
quency and rest intervals/days.
Range of Motion, Contraction Types and Resistance
Types
Range of Motion
The ACSM [4] failed to discuss range of motion
(ROM) in regard to muscular hypertrophy, which
might have been aresult of alack of available research.
Two studies have been published since the 2009 ACSM
recommendations [4] which are discussed herein.
Pinto et al. [94] investigated muscular hypertrophy of
the elbow flexors for partial and full range of motion
(ROM) repetitions for abilateral bicep ‘preacher’ curl
exercise. Untrained participants were divided in to
one of three groups; full ROM (where movement was
controlled at 0° to 130° flexion), partial ROM (where
movement was controlled as the mid part of the repeti-
tion [50-100° flexion]) and acontrol group who did
no exercise. The authors did not mention repetition
duration, and as such it is unclear as to whether they
controlled for the presumably longer contraction time
of agreater ROM repetition against asmaller ROM.
Using ultrasound, the authors reported no statistically
significant difference between the increases for full
and partial ROM muscle thickness (9.5% and 7.4%
respectively). It is therefore puzzling that the authors
concluded that afull ROM is essential for muscle mass
gains, even though their evidence does not support
this conclusion. Further evidence to support limited
ROM training comes from Eugene-McMahon and
Onambélé-Pearson [95] who examined the effects of
knee ROM using free weights, resistance machines and
bodyweight exercises for the lower body. Participants
were randomised to either apartial ROM (full exten-
sion to 50° knee flexion), full ROM (full extension to
90° knee flexion), or anon-training control group.
Muscle CSA was measured at baseline, 8, 10 and 12
weeks at 25%, 50% and 75% of femur length. Both
training groups showed significantly greater CSA at 8
weeks at all sites. For training groups hypertrophy was
still significantly greater than baseline at both 10 and
12 weeks at 50% and 75%. No significant changes were
found for controls at any time point. Between group
4 This equipment works on the principle that the concentric movement unwinds astrap and initiates aflywheel. Upon reaching full extension the strap
begins to rewind as aproduct of the kinetic energy of the rotating fly-wheel, thus pulling the lever arm back through the ROM. Participants resist this
secondary motion of the lever arm performing an eccentric phase to this exercise. See Norrbrand et al. [93] for further details.
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comparisons revealed only one significant difference
in favour of the full ROM group for CSA at 75% site
at week 8 compared to partial ROM.
Evidently significant hypertrophy occurs using
limited ROM resistance exercise; however, there is
contrasting evidence as to whether this differs from
the improvements induced by full ROM exercise ei-
ther for muscle thickness or site specific CSA [94,95].
Persons with injuries or diminished ROM might be
interested to find that this evidence suggests that
partial ROM repetitions can still produce significant
hypertrophic gains, with no discernible difference to
the gains made from repetitions performed through
afull ROM.
Contraction Types
The concept of contraction type is of important
consideration with regard to achieving optimal
hypertrophic gains. When performing an exercise
dependent upon gravity to provide resistance (e.g.
afree-weight or traditional weight stack orientated re-
sistance machine) there is adifference in muscle-fiber
recruitment and activation in favour of the concentric
(CONC) lifting of aweight compared to the eccentric
(ECC) lowering of aweight [96]. However, when using
flywheel (see previous footnote) or isokinetic equip-
ment the ability to overload the ECC phase by provid-
ing agreater load to resist applies adifferent resistance
type. The biomechanical nature of ECC training with
an isokinetic dynamometer means that the lever arm is
pulled away and the participant maximally resists that
movement. With atraditional resistance machine or
free weight the ECC phase is generally the lowering of
aload under control, rather than resisting the move-
ment. Of course an advanced technique in resistance
training, is to use asupra-maximal load (e.g. >1RM)
and perform negative repetitions, where persons
might apply force to resist the load, but be perform-
ing an ECC repetition since their force production is
lower than that of the load. Ultimately this might best
be considered in terms of intent. An isokinetic ECC
muscle action or supra-maximal negative repetition
is more like an intended CONC contraction, whereas
the ECC phase of anormal repetition is an intended
ECC muscle action. In fact, Blazevich et al. [97] stated
exactly this in their study of concentric and eccentric
muscle actions using isokinetic dynamometry for leg
extension exercises; that the ECC group “maximally
extended the knee to resist the downward movement of
the lever arm of the dynamometer”. Indeed, Moore et al.
[98] stated that due to the nature of eccentric isokinetic
training (e.g. resisting aload by attempting to perform
aconcentric contraction) there is agreater muscular
force than concentric training. With this in mind the
present section has divided training with isokinetic,
isoinertial and isometric contractions.
Isokinetic
Higbie et al. [99] considered the effects of concen-
tric (CONC) and eccentric (ECC) training of the knee
extensors on an isokinetic dynamometer. The authors
state that the previous maximal force was displayed on
ascreen and participants were encouraged to reach or
exceed that marker. Post-test MRI revealed signifi-
cantly greater increases in hypertrophy for the ECC
group (6.6%) compared to the CONC group (5.0%).
In contrast Blazevich et al. [97] reported no signifi-
cant differences in hypertrophy between CONC and
ECC groups performing an isokinetic knee extension
exercise at 30°/s, equating to approximately 3-seconds
for each concentric/eccentric muscle action. Finally
Farthing and Chilibeck [100] considered the effects of
concentric (CONC) and eccentric (ECC) training at
two different velocities (180°/s and 30°/s). Participants
performed either CONC or ECC training of the elbow
flexors on an isokinetic dynamometer. Following
a5-week washout period each participant performed
the opposite muscle action type on the opposing arm.
Muscle CSA was measured using ultrasound pre- and
post- intervention and results showed that ECC fast
training caused significantly greater hypertrophy (13
±2.5%) compared to CONC slow (5.3 ±1.5%), CONC
fast (2.6 ±0.7%), and both control group arms. In ad-
dition ECC slow training significantly increased CSA
(7.8 ±1.3%) compared to both control group arms. Nei-
ther fast nor slow concentric training velocities showed
any significant increase in CSA when compared to the
control group. The high velocity (180°/s) likely equated
to higher forces than the slower velocity (30°/s) when
resisted. This research suggests that eccentric actions
which require high muscular forces might be beneficial
in increasing muscular hypertrophy. However, due to
the unnatural nature of eccentric training with using
isokinetics, as well as the risks associated with supra-
maximal loads we should be cautious of inferring
practical application from this research.
Isoinertial
Housh et al. [101,102] conducted two separate
studies considering the effects of unilateral CONC
[101] and ECC [102] training using dynamic constant
external resistance (DCER) on the leg extensors. We
can consider both studies individually but also in
comparison since they utilised the same protocol
for testing and training whilst controlling the same
independent variables. For CONC training [101],
participants trained at 80% 1RM but the repetition
duration was not stated by the authors. Muscle CSA of
the thigh was measured by MRI where post-test results
revealed significant hypertrophy in the training group
only. In the second study, considering ECC training
[102], the same authors utilised an identical protocol
to previously [101], with the only change in variable
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being the use of ECC training as opposed to CONC
training. The lever arm and load was raised manually
and then the participant lowered the lever arm for
approximately 1-2seconds. Cross-sectional area was
measured via MRI, revealing no significant increases
in hypertrophy in the training or control groups pre-
to post-intervention. In comparison between these
studies it appears that the CONC training attained
significant hypertrophy where the ECC training did
not. However, we should consider that in the CONC
training study [101] the repetition duration was not
detailed, whilst the 1-2 seconds ECC training [102],
whilst prompting significant increases in 1RM, might
not be sufficient time-under-tension to promote
growth in muscle CSA in the quadriceps. As suggested
[96] CONC contractions appear to stimulate higher
motor unit activation than ECC muscle actions where
loads are equal, suggesting that the ECC group in the
study by Housh et al. [102] did not train to the same
intensity of effort as the CONC group [101]. Therefore,
greater gains in hypertrophy might have been possible
if performing ECC training with agreater load, or to
ahigher intensity of effort.
In consideration of exactly this Smith and Ruther-
ford [103] compared the effects of unilateral CONC
versus ECC training of the knee extensors on muscle
hypertrophy. The ECC exercise was performed with
aload 35% greater than CONC, and both ECC and
CONC repetitions were controlled at 3 seconds’ dura-
tion. Cross sectional area was measured using aCT
scan, revealing significant hypertrophy pre- to post-
intervention for both ECC and CONC groups (4.0%
and 4.6% respectively) with no significant difference
between limbs. In contrast Norrbrand et al. [93]
reported significantly greater increases for a group
training with ECC overload using aflywheel (FW)
compared to traditional loading (WS). The FW and
WS group performed 4 sets of 7 maximal repetitions
in ~3s (FW; 1.5 seconds concentric: 1.5 seconds ec-
centric, WS; 1 second concentric: 2 seconds eccentric).
Muscle volume of the quadriceps was measured using
MRI, revealing significant hypertrophy in both WS
and FW groups pre- to post- intervention. Whilst the
authors suggest agreater increase in hypertrophy for
whole quadriceps as aresult of FW compared to WS
they reported no statistically significant difference
between the groups (6.2% vs. 3.0%, respectively).
However, results for individual quadriceps muscles
revealedsignificantincreasesforvastuslateralis(VL),
vastusintermedius(VI), vastus medialis (VM) and
rectus femoris (RF) for the FW group, as opposed to
only RF for the WS group.
Other research with the lower body has been per-
formed by Walker et al. [104] who compared the effects
of CONC versus CONC and ECC (CONC + ECC)
training on muscle CSA in the gastrocnemius muscle.
Participants were randomly assigned to two training
groups, and each subject acted as his own control. The
CONC group performed 40° of plantar-flexion from
an ankle angle of 90°-130° for 2 seconds per repeti-
tion with a2 second rest between repetitions. whilst
the CONC + ECC group performed an identical pro-
tocol with the addition of a2 second eccentric phase
as opposed to the 2 second rest. Muscle CSA of the
gastrocnemius measured by MRI revealed significant
increases in the CONC + ECC group only. Research
has also considered upper body muscles; Brandenburg
and Docherty [105] compared the effects of accentu-
ated eccentric loading on muscle hypertrophy of the
elbow flexors and extensors. Trained participants were
divided between dynamic constant external resistance
(DCER) and dynamic accentuated external resistance
(DAER). Participants in both groups performed either
4 sets of 10 repetitions at 75% 1RM (DCER) or 3 sets
of 10 repetitions at 75% 1RM for the concentric phase,
and 125% concentric 1RM for the eccentric phase
(DAER). Repetition duration was controlled at 2 sec-
onds concentric: 2 seconds eccentric for both groups.
Muscle CSA was measured pre- and post-intervention
using MRI at the mid-point of the humerus. However,
results revealed no significant hypertrophy in either
flexors or extensors in either DCER or DAER. The
authors attributed the lack of significant increases in
CSA to the trained status of the participants.
This evidence suggests that both concentric and ec-
centric muscle actions are required to stimulate muscle
hypertrophy. In addition, since muscle fibre recruit-
ment appears diminished in an eccentric compared
to concentric action when using the same load [96],
this research supports methods which increase the
intensity of effort, and thus muscle fibre recruitment,
in eccentric phases of amovement (e.g. by increasing
repetition duration or load).
Isometric
Finally multiple studies have considered isometric
training; Jones and Rutherford [106] compared the
effects of concentric (CONC), eccentric (ECC) and
isometric (ISO) training of the knee extensors. The
ISO group performed 4 second contractions at aknee
angleof90°anda targetof80% MVC.MuscleCSA
was measured pre- and post-intervention revealing
significant hypertrophy, with no significant differences
between training intervention groups. Similar results
have been reported for isometric training of the knee
extensors by Garfinkel and Cafarelli [107] and Kubo
et al. [108]. The training group within Garfinkel and
Cafarelli [107] performed thirty unilateral maximal
voluntaryisometriccontractions(MVIC)oftheknee
extensors. Muscle CSA measured by CT scan showed
significant hypertrophy pre- to post-intervention
(14.6%). The participants within Kubo et al. [108]
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performed two different unilateral isometric knee
extension regimes; either 3 sets of 50 repetitions for
1 second contraction and 2 second relaxation (short
duration), or 4 sets of acontraction for 20 seconds
and relaxation for 1 minute (long duration). Muscle
volume was calculated from MRI revealing significant
increases in hypertrophy in both legs (short duration
= 7.4 ±3.9%, and long duration = 7.6 ±4.3%) with no
significant between group differences.
Research also supports the use of isometric training
for the upper body. For example Ikai and Fukunaga
[109] measured muscle hypertrophy following uni-
lateral isometric training of the elbow flexors (at an
angle of 90°). Participants performed 3 x 10 second
maximal isometric contractions every day (except
Sunday) for 100 days. Ultrasound results revealed
significant hypertrophy pre- to post-test, in the trained
arm only, at 40 and 100 days (P < 0.05 and P < 0.001,
respectively). Davies et al. [110] also considered the
effects of unilateral isometric (IM) elbow flexion, this
time at 80% of maximal isometric torque. At 90° of
elbow flexion each participant performed 4 sets of 6
IM contractions, with each contraction lasting for 4
seconds. Maximal IM torque was tested each week to
accommodate aprogressive increase throughout the
6-week programme. Cross-sectional area was mea-
sured using CT scan revealing significant hypertrophy
in the trained arm only. In addition, and as discussed
previously Gondin et al. [64] reported data that sug-
gested that electrically stimulated isometric training of
thequadricepsat~68%MVCissufficienttostimulate
hypertrophic gains.
The research considered herein suggests that
muscular hypertrophy can be obtained by concentric
[97,101,103] eccentric [93,99,100] and isometric
muscle actions [64,106-110]. There appears to be
some evidence to suggest greater gains are acquired
from the disproportionate loading and contraction
type during eccentric muscle actions performed using
an isokinetic dynamometer [99,100]. However, other
studies have shown no significant difference between
constant and negative accentuated resistance [105],
and others have suggested no significant difference
in the hypertrophic gains achieved from isometric,
concentric and eccentric muscle actions [106]. Ulti-
mately it, once again, appears that amuscle action type
that maximally recruits motor units and thus muscle
fibres appears optimal to stimulate hypertrophic gains
whether that be eccentric, concentric, or isometric.
Resistance Types
The evidence presented suggests that hypertrophic
gains can be acquired by free-weight [78], traditional
accommodating resistance machines [65,66,71,86],
flywheel machines [93,111,112], and isokinetic dy-
namometers [97,100]. However, only one published
study has specifically considered the differences in
hypertrophy between resistance types. O’Hagan et al.
[113] considered the effects an accommodating elbow
flexion resistance machine (hydraulic; ARD), and the
other arm using aweight resistance machine (designed
to the same specification as the ARD but using acable
pulley; WRD). It is worth noting that the ARD group
only performed contractions in the CONC phase (each
repetition at, or near maximal), whilst the WRD group
trained using CONC and ECC muscle actions at 80%
1RM5. The ARD group performed CONC contractions
on the slowest possible setting, which was replicated
on the WRD using ametronome. Interestingly the
authors commented that they equated workload in
“units” [page 1213]. However, if the WRD group truly
performed their sets to repetition maximum (RM)
then the main consideration is simply that both groups
trained to maximal effort; the ARD group performed
10 maximal concentric contractions per set, and the
WRD group performed 1 maximal concentric contrac-
tion as the final repetition of each set. The use of CT
scan revealed significant hypertrophy for both groups
post-test. They reported no significant between group
difference for biceps CSA, or total flexor CSA; however
they did report asignificantly greater increase in CSA
in the brachialis for the WRD group.
Summary
The evidence suggests that muscular hypertrophy
can be obtained through concentric, eccentric and
isometric muscle actions, with the most significant
variable appearing to be that of intensity of effort and
thus muscle fibre recruitment. We suggest that use of
an isokinetic dynamometer or resisting supramaximal
loads (e.g. >1RM) for eccentric muscle actions pro-
vides asignificant stimulus for growth. However, we
urge caution with regard to the safety implications of
using supramaximal loads.
In addition, whilst there is minimal research that
has directly compared hypertrophy when training
with different resistance types, the evidence presented
supports the logical conclusion that amuscle does not
know what it contracts against; it simply contracts or
relaxes [61]. Therefore, we reiterate earlier comments;
that it is the recruitment of motor units and muscle
fibres that stimulates muscular growth irrespective of
what has caused that recruitment. With this in mind,
and until further evidence can suggest to the contrary,
there appears no scientific reason for suggesting one
resistance type above another, but rather to propose
5 The authors provide adiagrammatic to show that the WRD group trained at 80% of “maximal contraction”, however we should clarify that this is
areference to the load lifted in asingle repetition (page 1212; e.g. 1RM), in fact the WRD group trained at 8-12RM which by its definition means that the
final repetition was amaximal contraction irrespective of the load being lifted.
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that it is the method of training that appears more
important. We propose that resistance type should be
chosen with the consideration of other variables, e.g.
safety, time efficiency, and personal preference.
Non-Uniform Muscle Growth, Contralateral Effects,
and Training and Detraining Time-Course
Non-Uniform Muscle Growth
In areview of muscular hypertrophy we should
also consider the non-uniform growth of both asingle
muscle along its length and of individual muscles
within agroup, as it might be expected by some that
they should confer uniform hypertrophy from par-
ticipation in resistance training. Examination of the
research in this area suggests need for amore reserved
expectation. For example research has supported
non-uniform hypertrophy of the quadriceps muscles
as aresult of resistance training. Research suggests
that lower body exercise stimulates the greatest level
of hypertrophic growth at the rectus femoris, with
lesser and similar results from the vastus medialis
and lateralis and the least hypertrophy at the vastus
intermedius [92,111,112,114].
In support of non-uniform growth Abe et al. [115]
considered whole body hypertrophy. Three physically
active, but untrained, males performed 16 weeks of
resistance training, performing squat, knee extension,
knee flexion, bench press and lat pull-down exercises
for 3 sets of 8-12 repetitions to failure. Total body MRI
revealed significant pre- to post- intervention increases
in muscle volume, with the most significant hypertro-
phy occurring at the level of the shoulder, chest, and
upper portion of the upper arm (m=26%), followed
by the mid-thigh (m=18%) and lower leg (m=9%).
Matta et al. [116] considered muscle thickness of the
biceps brachii (BB) and triceps brachii (TB) following
an upper body resistance training intervention. Mus-
cular hypertrophy was measured using ultrasound at
proximal (PS), midsite (MS) and distal (DS) positions
of the humerus (50, 60, and 70% distance between
the acromion and olecranon, respectively). Results
revealed significant hypertrophy for BB at all sites
after the training intervention. In addition pre- and
post- intervention data revealed significant differences
in MT at the PS (~12%) and DS (~5%) (P < 0.05). Sig-
nificant hypertrophy was also seen in the TB pre- to
post-intervention at PS, MS, and DS sites. However,
there was no significant difference in the proportion
of hypertrophy between sites on the TB.
Similar research which has considered the activa-
tion of muscles has been performed by Wakahara
et al. [117] who considered muscle activation and
hypertrophy of the triceps in distal, middle and proxi-
mal regions. Acute muscle activation was reported as
aproduct of MRI measurements taken before and after
asingle workout. The authors suggest that brightness
of the agonist muscle in aMRI increases immediately
after exercise, which can be quantified as an increase
in the transverse relaxation time (T2) of amuscle.
The authors suggest this has been related to exercise
intensity, number of repetitions and electrical activ-
ity. Results showed significantly lower activation in
the distal region of the triceps compared to middle
and proximal regions. Similarly the chronic increases
in muscle CSA was significantly lower in the distal
region compared to the middle and proximal regions.
In amore recent study the same authors [118] followed
asimilar research design with supportive results. Once
again MRI was used to estimate muscle activation of
the triceps brachii using transverse relaxation time
of the triceps. Pre- to post-intervention hypertrophy
supported that the most significantly activated areas of
the muscle result in the greatest hypertrophic change.
These authors suggested that the chronic adaptations
of muscle hypertrophy are attributable to the acute
muscle activation during the exercise. Of course it
is logical that to stimulate muscular growth we must
activate the motor units and muscle fibres.
In review Hedayatpour and Falla [119] suggest that
non-uniform muscular adaptations are aproduct of
the individual muscle fibres’ mechanical and direc-
tional biology, stating that architectural complexity’
along with the ‘non-uniform distribution of motor
unit activation during exercise influence this. In sum-
mary, it appears that whilst different exercises might
activate different areas of a muscle there is a more
complex relationship between motor-unit activation,
fibre-recruitment and chronic hypertrophy for specific
exercises than the present review can consider.
Contralateral effects
As an adjunct to non-uniform growth it is perhaps
worth discussing the concept of contralateral effects
of unilateral training, i.e. agrowth effect in an un-
trained limb as aresult of training the contralateral
limb. In the future section on time-course of train-
ing and detraining, we discuss astudy by Ivey et al.
[120], who presented data that unilateral training of
the knee-extensors can produce contralateral effects
in males. However, other research has suggested that
training unilaterally causes significant hypertrophy
in the trained limb only considering the elbow flex-
ors [109], elbow extensors 121] and knee extensors
[101,102,111,112,122,123].
Further evidence comes from Ploutz et al. [124]
who considered the hypertrophic effects of unilateral
knee extension training. Cross-sectional area of the
thigh was measured pre- and post-intervention using
MRI, with results reporting asignificant mean increase
in hypertrophy in the trained leg only. The CSA of
the untrained leg showed no significant change pre-
post-intervention (neither hypertrophy nor atrophy).
228
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
Whilst it is not within the scope of this article to con-
sider strength changes as aresult of any RT studies, it
is perhaps noteworthy that whilst the left quadriceps
made greater 1RM strength changes than the right leg
(14% vs. 7%), both legs showed asignificant increase in
1RM strength pre- post-test, suggesting that there was
astrength but not hypertrophic response in the un-
trained leg. Tesch et al. [112] considered the effects of
unilateral unloading with the addition of knee exten-
sion resistance exercise over a5 week period. Muscle
volume was measured pre- and post-intervention
using MRI, revealing significant hypertrophy in the
quadriceps as aresult of training. The authors reported
significantincreasesforeachquadricepsmuscle(VL=
6.2%,VI=5.3%,VM=9.3%,andRF=16.3%)aswell
as whole quadriceps (7.7%). The other participants
who were subject to unilateral unloading without
resistance training showed significant reductions in
musclesize(VL=-9.3%,VI=-8-8%,VM=-12.1%,
RF = 0%, whole quadriceps = -8.8%.
Finally, Hubal et al. [125] considered hypertrophy
of males and females performing unilateral biceps and
triceps exercise in their non-dominant arm. A large
cohort of participants (male=243, female=342) per-
formed biceps preacher curl, biceps concentration curl,
standing biceps curl, overhead triceps extension and
triceps kickback. Muscle CSA of the elbow flexors was
measured pre- and post-intervention using MRI at asite
corresponding to the maximum circumference when
the elbow was flexed to 90°. Results revealed asignifi-
cant increase in muscle size for both males (20.4%) and
females (17.9%), with asignificant difference between
groups (p < 0.001). No significant increases were seen in
the untrained arm in either males or females. Interest-
ingly, due to the large sample size, the authors were able
to comment regarding outliers, defined as ±2 SD. They
reported that 0.08% of both men (n = 2) and women (n
= 3) were low responders, and that 3% of men (n = 7)
and 2% of women (n = 7) were high responders. Indeed,
in Figure. 1 [page 968] the range of percentage increases
in CSA change is considerable from -5% to +55%. This
shows that inter-individual differences in hypertrophic
response to training are substantial.
The evidence generally supports that hypertrophy
is not commonplace as aresult of contralateral train-
ing with the exception of the study by Ivey et al. [120].
Interestingly within their study the authors make clear
that “the untrained leg was kept in arelaxed position
throughout the training program… and verified by
constant investigator observation”. In addition whilst
the authors do confirm their data in the results sec-
tion, clarifying that “the small change seen in untrained
limbs in both older and younger men was significant (P
< .05)”they fail to discuss this result at all in the discus-
sion section. As such it is difficult to hypothesise as to
why they obtained such abnormal results.
Training and Detraining Time course
For those engaged in resistance training it is of
interest to understand how quickly they can expect to
begin to acquire hypertrophic adaptations. Similarly,
for those presently engaged in resistance training,
reasons may arise that may require them to halt their
engagement for aperiod of time, thus leading us to
consider to what extent initial adaptations might be
maintained or lost. Thus within the present article
it seems prudent to discuss expected time-course
of muscular growth as aresult of resistance training
in addition to the expected time-course of muscle
response to detraining. For example Seynnes et al.
[81] reported significant increases in hypertrophy of
thequadricepsmuscles(RF,VM,andVL),measured
using MRI, after 20 days of resistance training (4 sets
of 7 ‘maximal’ repetitions performed on aflywheel
bilateral leg extension 3 x / week).
Abe et al. [126] considered the effect of time course
and volume of training on whole-body muscular
hypertrophy with untrained participants (male=17,
female=20), aged 25-50 years. Muscle thickness was
measured using ultrasound at the following eight ana-
tomical sites; chest, anterior and posterior upper arm,
anterior thigh (30%, 50%, and 70% thigh length from
greater trochanter) and posterior thigh (50% and 70%
of thigh length) pre- and post-intervention, and at 2
week intervals throughout the 12 weeks. Significant
increases occurred in the upper body (males’ biceps at
4 weeks, and the males’ and females’ triceps and chest
at 6 weeks, continuing to increase through weeks 8
and 12) and lower body (males’ hamstrings muscles;
50% from greater trochanter at 6 weeks, males’ and
females’ hamstrings muscles; 70% from greater tro-
chanter at 6 weeks). Some significant improvements
were seen post-intervention compared to weeks 2, 4
and 6 in the upper body. No significant increases in
muscle thickness were reported for the quadriceps for
males or females. We might consider the motivation
of the participants to train to muscular failure, or even
consider the potential for low response as aresult of
genetics as suggested by Hubal et al. [125] as reasons
for alack of hypertrophy.
Amore recent study reported that untrained males
performing abench press exercise can significantly (P
= 0.002) increase muscular hypertrophy of the pectora-
lis major (PM) after just 1 week of training as measured
by ultrasound [82]. Whilst the authors reported PM
and TB increases at weeks 1 and 5, respectively; the
table shown on page 219 does not provide data for
individual weeks, only 3- week intervals. Interestingly
from this table we can see that both PM and TB showed
significant increases in muscle thickness at week 3,
leading us to question why in the results section they
state TB increases at week 5. The authors also reported
that the pectoralis major showed steady increases in
229
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
size throughout the duration of the 24-week interven-
tion (weeks 3 and 6 were significantly greater than pre-
testing, whilst weeks 9, 12 and 15 were significantly
greater than week 6, and week 24 was significantly
greater than week 15). Whereas the triceps brachii
made early increases in hypertrophy (weeks 3 and 6
were significantly greater than pre-testing, and week
15 was significantly greater than week 6), no signifi-
cant differences were found when comparing weeks
18, 21 and 24 to week 15. It is perhaps worth noting
that participants performed the bench press exercise
at 200% of the biacromial distance, which the authors
suggest might have resulted in decreased activation of
the triceps [127].
In addition multiple studies have considered
detraining periods. For example Narici et al. [123]
considered hypertrophic changes following 60-days
of isokinetic knee extension training, and a40-day
detraining period. Cross sectional area was measured
using MRI pre- and post-intervention, revealing
significant increases in hypertrophy over the 60 day
period (8.5 ±1.4%, equating to approximately 0.14%
/ day). Similar significant decreases in hypertrophy
(0.10% / day) were reported following the 40 day de-
training period. In contrast Ivey et al. [120] reported
that the significant increases in hypertrophy as aresult
of 9-weeks of knee extension exercise were still evident
after 31 weeks without any additional training, in pre-
viously untrained males. However, whilst untrained
females also showed asignificant increase in muscle
volume following the 9-week resistance training
intervention the MRI results following detraining
suggested that their quadriceps had atrophied to their
original size pre-training. Alater study by Blazevich
et al. [97], reported significant growth following 10
weeks of isokinetic knee extension exercise. In addi-
tion, following afurther 14 weeks of detraining there
was no significant difference in MT between finishing
the training intervention and finishing the detraining
period. However, data analysis also revealed that there
was no statistically significant difference in MT be-
tween the starting (pre-training intervention) values,
and the values after the detraining period.
Finally Ogasawara et al. published two studies
comparing continuous and non-continuous resistance
training [128,129]. The earlier study [128] compared
two groups, performing either continuous training for
15 weeks (CTR) or agroup that trained for 6 weeks,
went untrained for 3 weeks, and then retrained for
afurther 6 weeks (RTR) using free-weight bench press.
The initial 6-weeks showed significant increases in
hypertrophy of the triceps brachii (TB) and pectoralis
major (PM) with no significant difference between
CTR and RTR groups. During the 3-week detraining
period the RTR group showed no significant atrophy
of the TB and PM. Through the final 6 weeks of the
intervention the CTR group reported asignificantly
decreased hypertrophy in the TB and PM when com-
pared to the initial 6 weeks, whereas the RTR group
showed no such decrease in rate of growth. At the
conclusion of the 15-week intervention there was no
significant difference in hypertrophy of the TB and
PM between the CTR and RTR groups. In the more
recent study Ogaswara et al. [129] again considered
TB and PM hypertrophy following abench press
exercise, this time comparing continuous (CTR) and
periodized (PTR) training groups. The continuous
training group performed the exercise for 24 consecu-
tive weeks, whilst the periodised group performed the
exercise for weeks 1-6, 10-15, and 19-24 with 3-week
detraining period in between. In the CTR group hy-
pertrophic changes were significantly greater for weeks
1-6, compared to weeks 10-15, and 19-24. However,
in the PTR group there was no significant difference
in the rate of growth between weeks 1-6, 10-15, and
18-24. When comparing measurements between the
groups at week 6, 15 and 24 there were no significant
differences for either PM or TB suggesting that any
atrophy over the detraining periods was compensated
for over the subsequent 6-week training periods.
Summary
The evidence considered within this section sug-
gests that non-uniform muscle growth (in both asingle
muscle as part of agroup, and along the length of abel-
ly of amuscle) is commonplace. We suggest that whilst
different exercises/body positions/handgrips might
activate different areas of a muscle there is a more
complex relationship between motor-unit activation,
fibre-recruitment and chronic hypertrophy than the
present review can consider. With this in mind our
suggestion is to perform avariety of upper and lower
body exercises, utilizing divergent grips and body posi-
tions (within safe boundaries) to ensure comparable
hypertrophy for the entire muscular system.
In addition there appears little evidence to suggest
that contralateral hypertrophy can be obtained. Finally,
the time course for hypertrophy appears to occur
following around 3-4 weeks of resistance training.
However, more notably, the time course for muscular
atrophy appears to vary considerably between persons.
It appears that rest from training or abrief detraining
period does not result in significant atrophy and can,
in fact, increase hypertrophy when returning to resis-
tance training. This seems logical; that the body does
not grow during training, but rather whilst recovering
from the training stimulus. Brief periods of excessive
training require asimilar period of no training to allow
the body to recover and prepare for further training
sessions. Further research should certainly investigate
frequency of training to consider optimal timescale for
training and recovery between workouts.
230
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
Training status and Genetics
The present article has not considered the dispar-
ity in hypertrophy between trained and untrained
individuals, primarily because most research studies
utilize untrained participants, and due to the vague
interpretations of trained, untrained, and recreation-
ally trained.6 However, we should also recognize that
once aperson is in some degree of trained state that
their rate of response is likely to diminish. We suggest
that future research needs to consider this area in
greater detail regarding manipulation of the variables
discussed herein. However, we should recognise that
within the final section discussing detraining, it ap-
pears that lengthy recovery from previous training
interventions does not cause significant atrophy and
can accommodate substantially greater hypertrophy
when returning to training. With this regard our
recommendation is to monitor training response,
perhaps through the use of atraining journal, and
provide sufficient variation and rest and recovery to
allow muscular hypertrophy to occur.
In addition, and as mentioned in the opening
section, we should identify that genetic factors will
likely be the most significant variable with regard to
hypertrophic response to resistance training, [28,29]
though unlike the manipulation of training variables
these cannot be manipulated. Aprevious review con-
sidering strength training [61] identified and discussed
the generally accepted somatotypes and genotypes
that appear to affect responsiveness to training. In-
deed, as noted previously Hubal et al. [125] reported
that 0.08%, and 3% of his 585 participants were low
responders and high responders respectively, caus-
ing changes in CSA varying between -5% and +55%.
In consideration of this, those engaged in resistance
training for hypertrophy should mediate their expecta-
tions accordingly, though realise that the potential for
positive hypertrophic adaptations is inherent in the
vast majority of people yet to varying degrees [125].
Afinal note on methods of measuring muscular
development is that of muscle density as measured
using Hounsfield units by CT scan. Previous research
has reported an increase in muscle density [130,131]
as aresult of resistance training, which whilst not
ameasure of muscle cross sectional area (and as such
has not been included within the present article) is
achange in muscle architecture. Many persons re-
cord increases in muscular strength without change
in muscle cross sectional area [e.g. 105]; perhaps the
unmeasured muscular density needs to be considered
more in future research.
Conclusion
This article presents evidence-based recommenda-
tions for persons wishing to increase their muscular
size. In summary, the evidence discussed herein leads
us to suggest that intensity of effort should be maximal
to recruit, and thus stimulate the growth of, as many
muscle fibres as possible by training to momentary
muscular failure [63-66]. Single sets of exercises appear
to attain similar results to multiple sets [84-86,88], and
load used and number of repetitions performed seems
not to affect hypertrophy where sets are taken to MMF
[67-74], whilst repetitions should be performed at
apace that maintains muscular tension [70,71,78]. In
addition, long rest intervals appear unnecessary [74,83]
and the inclusion of concurrent endurance training
appears not to significantly influence the hypertrophic
gains of resistance training [89,90,92]. In fact, the ad-
dition of high intensity cycling might increase mus-
cular hypertrophy [92]. Neither the type of resistance
[65,66,71,78,97,100,111-113], range of motion [94,95]
nor muscle action (e.g. concentric, eccentric or isomet-
ric; [64,97,103-105,108] seem to influence muscular
growth, although evidence suggests the likelihood of
non-uniform muscle growth both along the length of
amuscle and between individual muscles of amuscle
group [92,111,112,114-118]. Exercising acontralateral
limb appears not to stimulate hypertrophic gains in an
untrained limb, although evidence suggests that it might
reduce the rate of atrophy [124,125]. Finally untrained
persons appear to be capable of making significant hy-
pertrophic gains within 3 weeks of starting resistance
training [81,88] whilst trained persons are encouraged
to allow adequate rest (up to ~3 weeks) [122,128,129]
between training sessions without fear of atrophy.
Future Research
Interestingly, amid the plethora of studies reviewed
there was no research that had compared frequency
of training, and/or differing routine types (e.g. whole
body and split routine) both of which are likely of
considerable interest to both exercise physiologists
and lay persons wishing to increase muscularity. Fu-
ture research should certainly consider these areas,
along with those others mentioned herein in similarly
well-controlled studies. We reiterate earlier comments
about the control and detail of independent variables
to ensure that published research provides adequate
information, rather than simply the publication of data
which, whilst attempting to replicate real-life resistance
training programs, lacks sufficient scientific rigour to
be replicated or utilised optimally.
6 The ACSM [4] define novice, intermediate and advanced persons by their duration of training experience (novice being untrained or having not
trained for several years, intermediate being individuals with ~6 months RT experience, and advanced being individuals with years of RT experience).
However, we suggest that this offers little as to clarify their training status and assumes that persons with agreater duration of RT have acquired greater
knowledge, experience and physiological adaptations, which might not necessarily be the case.
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Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
Table 1. Evidence for Resistance Training Recommendations
Topic Recommendation Supporting
Articles Suggestions for Future Research
Intensity of Effort Persons should aim to recruit as many
motor units, and thus muscle fibres, as
possible by training until momentary
muscular failure.
63-66 Future research should consider
the use of advanced training
techniques such as drop-sets/
breakdown sets, pre-/post-
exhaustion training.
Load and Repeti-
tion Range
Persons should self-select a weight and
perform repetitions to failure. Evidence
suggests this is optimal for maximising
hypertrophy.
67-74
Repetition Dura-
tion
Persons should perform contractions at a
repetition duration that maintains mu-
scular tension.Performing repetitions too
briefly appears to unload the muscle and
hinder hypertrophic gain
70, 71, 78-80
Rest Intervals Length of rest interval between sets and/
or exercises appears to have no significant
effect on hypertrophic gain. Persons sho-
uld self-select rest intervals based on their
available time.
74, 83
VolumeandFre-
quency
Single set training appears to provide
similar hypertrophic gains to multiple set
training. Frequency of training should be
self-selected as there appears no evidence
which can support any recommendation.
See also ‘Training and detraining Time
course’
84-87 Future research should investi-
gate frequency of training, for
which there appears no current
research, as well as multiple sets
with a single exercise compa-
red to single sets with multiple
exercises.
Concurrent Resi-
stance and Endu-
rance Training
The participation in traditional endurance
exercise does not appear to hinder hyper-
trophic gains from resistance training.
89, 90, 92 Future research should consider
concurrent upper/whole- body
aerobic exercise, such as arm-
-cranking/rowing exercise, com-
bined with resistance training.
Range of Motion
(ROM)
Persons can self-select the ROM they exer-
cise through. There appears no evidence
to suggest that decreased ROM negatively
affects muscular hypertrophy.See also
‘Non-Uniform Muscle Growth
94, 95 Future research should consider
other muscles; e.g. lower back,
knee flexors, and elbow exten-
sors, as well as other exercises;
e.g. squat/leg press, chest press,
and shoulder press.
Contraction
Types
We recommend that persons should
complete a range of concentric, eccentric
and isometric muscle actions as part of
their resistance training programme. There
appears no evidence to suggest that one
muscle action type is more favourable than
another, but rather intensity of effort of
said muscle actions appears to be the most
significant variable.
64, 97, 103-105,
108
Resistance Type Persons should select resistance type based
on personal choice. Evidence appears to
suggest hypertrophy is attainable using
free-weights, machines or other resistan-
ce types. However, studies making direct
comparisons are minimal.
65, 66, 71, 78, 97,
100, 111-113
Future research should accura-
tely control for intensity of effort
and directly compare body-we-
ight training, free-weights, and
different resistance machines to
further investigate as to whe-
ther one resistance type is more
efficacious than another
232
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
Non-Uniform
Muscle Growth
Persons should perform a variety of exer-
cises/body positions/hand-grips to activate
different areas of a muscle in attempt to
stimulate hypertrophy. Evidence suggests
that non-uniform muscle growth in single
muscles within a group, and along the belly
of a muscle, is commonplace, and poten-
tially beyond the control of an individual.
92, 111, 112, 114-
118
Contralateral
Effects
Persons cannot obtain hypertrophic in-
creases by training contralateral muscles.
However, doing so might cause a reduction
in atrophy of an immobilised limb.
124, 125
Training and
Detraining Time-
-Course
Untrained persons appear able to make
hypertrophic increases in around 3 weeks
of resistance training.Trained persons
performing regular resistance training are
encouraged to allow adequate rest between
training sessions without fear of atrophy.
Brief (~3 weeks) absences from training
appear not to cause significant atrophy and
potentially promote greater hypertrophy
upon return to training.
81, 82, 122, 128,
129
Author disclosures
The authors have no conflicts of interest to declare
and received no external funding. This article is in
no way affiliated with any health, fitness or exercise-
related organisation.
References
1. Schoenfeld BJ. The mechanisms of muscle hypertrophy and
their application to resistance training. J Strength Cond Res
2010; 24(10): 2857-72.
2. Wolfe BL, LeMura LM, Cole PJ. Quantitative analysis of
single- vs. Multiple-set programs in resistance training. J
Strength Cond Res 2004; 18(1): 35-47.
3. Wernbom M, Augustsson J, Thomeé R. The influence of
frequency, intensity, volume and mode of strength training
on whole muscle cross-sectional area in humans. Sports Med
2007; 37(3): 225-64.
4. Ratamess NA, Alvar BA, Evetoch (sic) TK, et al. Progression
models in resistance training for healthy adults. Med Sci Sports
Exerc 2009; 41: 687-708.
5. Krieger J. Single vs. Multiple sets of resistance exercise for
muscle hypertrophy: ameta-analysis. J Strength Cond Res
2010; 24(4): 1150-9.
6. Kraemer WL, Adams K, Cafarelli E, et al. American College
of Sports Medicine position stand. Progression models for
resistance training in healthy adults. Med Sci sports Exerc
2002; 34: 364-80.
7. ZatsiorskyVM.Science and Practice of Strength Training.
Champaign, IL: Human Kinetics; 1995.
8. Winett RA. Meta-Analyses do not support performance
of multiple sets or high volume resistance training. J Exerc
Physiol 2004; 7(5): 10-20.
9. Carpinelli RN. Challenging the American college of sports
medicine 2009 Position stand on resistance training. Med
Sport 2009; 13(2): 131-7.
10. Fisher J. Beware the meta-analysis; is multiple set training re-
ally better than single set training for muscular hypertrophy?
J Exerc Physiol 2012; 15(6): 23-30.
11. Charette SL, McEvoy L, Pyka G, et al. Muscle hypertrophy in
response to resistance training in older women. J Appl Physiol
1991; 70(5): 1912-6.
12. Janssen I, Shepard DS, Katzmarzyk PT, et al. The healthcare
costs of sarcopenia in the United States. J Am Geriatr Soc
2004; 52: 80-5.
13. Kosek DJ, Kim J, Petrella JK, et al. Efficacy of 3 days/wk
resistance training on myofiber hypertrophy and myogenic
mechanisms in young vs. older adults. J Appl Physiol 2006;
101: 531-44.
14. Debigaré R, Côté CH, Maltais F. Peripheral Muscle wasting
in chronic obstructive pulmonary disease; clinical review and
mechanisms. Am J Respir Crit Care Med 2001; 164(9): 1712-7.
15. Dolan SA, Frontera W, Librizzi J, et al. Effects of asupervised
home-based aerobic and progressive resistance training regi-
men in women infected with human immunodeficiency virus.
Arch Intern Med 2006; 166(111): 1225-31.
16. Antonio J. Nonuniform response of skeletal muscle to heavy
resistance training: Can bodybuilders induce regional muscle
hypertrophy? J Strength Cond Res 2000; 14(1): 102-13.
17. Hackett DA, Johnson NA, Chow CM. Training Practices and
Ergogenic Aids used by Male Bodybuilders. J Strength Cond
Res 2012; IN PRESS.
18. Sader MA, Griffiths KA, McCredie RJ, et al. Androgenic
anabolic steroids and arterial structure and function in male
bodybuilders. J Am Coll Cardiol 2001; 37(1): 224-30.
19. Saugy M, Robinson N, Saudan C, et al. Human growth hor-Human growth hor-
mone doping in sport. Br J Sports Med 2006; 40: suppl i35-9.
20. Olshansky SJ, Perls TT. New development in the illegal pro-
vision of growth hormone for “anti-aging” and bodybuilding.
J Am Med Assoc 2008; 299(23): 2792-4.
21. Ahtiainen JP, Pakarinen A, Alen M. Muscle hypertrophy,
hormonal adaptations and strength development during
strength training in strength-trained and untrained men. Eur
J Appl Physiol 2003; 89: 555-63.
22. VellosoCP.Regulationofmusclemassbygrowthhormone
and IGF-1. Br J Pharmacol 2008; 154(3): 557-68.
23. West DWD, Phillips SM. Associations of exercise-induced
hormone profiles and gains in strength and hypertrophy in
alarge cohort after weight training. Eur J Appl Physiol 2012;
112: 2693-702.
24. VierckJ,O’ReillyB,HossnerK,etal.Satellitecellregulation
following myotrauma caused by resistance exercise. Cell Biol
Int 2000; 24: 263-72.
25. Adams GR. Satellite cell proliferation and skeletal muscle
hypertrophy. Appl Physiol Nutr Metab 2006; 31(6): 782-90.
233
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
26. Chesley A, MacDougall JD, Tarnopolsky MA, et al. Changes
in human muscle protein synthesis after resistance exercise.
J Appl Physiol 1992; 73(4): 1383-8.
27. Burd NA, Andrews RJ, West DWD, et al. Muscle time under
tension during resistance exercise stimulates differential
muscle protein sub-fractional synthetic responses in men. J
Physiol 2012; 351-62.
28. Lutoslawska G, Tkaczyk J, Keska A. Myostatin and its role
in the regulation of muscle mass and metabolism. Med Sport
2012; 16(4): 165-74.
29. Stewart CEH, Rittweger J. Adaptive processes in skeletal
muscle: Molecular regulators and genetic influences. J Mu-
sculoskelet Neuronal Interact 2006; 6(1): 73-86.
30. Sharples AP, Stewart CE. Myoblast models of skeletal muscle
hypertrophy and atrophy. Curr O pin Clin Nutr 2011; 14: 230-6.
31. Schoenfeld BJ. Potential mechanisms for arole of metabolic
stress in hypertrophic adaptations to resistance training.
Sports Med 2013; 43: 179-94.
32. West DW, Kujbida GW, Moore DR, et al. Resistance exerci-
se-induced increases in putative anabolic hormones do not
enhance muscle protein synthesis or intracellular signalling
in young men. J Physiol 2009; 587: 5239-47.
33. West DWD, Burd NA, Staples AW, et al. Human exercise-
mediated skeletal muscle hypertrophy is an intrinsic response.
Int J Biochem Cell Biol 2010; 42: 1371-5.
34. Carpinelli RN. Acritical analysis of the claims for the
inter-set rest intervals, endogenous hormonal responses,
sequence of exercise, and pre-exhaustion exercise for opti-
mal strength gains in resistance training. Med Sport 2010;
14(3): 126-56.
35. Carpinelli RN. Resistance exercise induced acute hormonal
responses and chronic adaptations: Anull field? Med Spor t
2011; 15(1): 41-3.
36. Phillips SM. Strength and hypertrophy with resistance tra-
ining: chasing ahormonal ghost. Eur J Appl Physiol 2012;
112: 1981-3.
37. Howell JN, Chleborn G, Conatser R. Muscle stiffness, strength
loss, swelling and soreness following exercise-induced injury
in humans. J Physiol 1993; 464: 183-96.
38. Nosaka K, Clarkson PM. Changes in indicators of inflam-
mation after eccentric exercise of the elbow flexors. Med Sci
Sports Exerc 1996; 28: 953-61.
39. Howatson G, Milak A. Exercise induced muscle damage
following about of sport specific repeated sprints. J Strength
Cond Res 2009; 23: 2419-24.
40. Tesch PA, Larsson L. Muscle hypertrophy in bodybuilders.
Eur J Appl Physiol Occup Physiol 1982; 49: 301-6.
41. Paul AC, Rosenthal N. Different modes of hypertrophy in
skeletal muscle fibers. J Cell Biol 2002; 18(156); 751-60.
42. Toigo M, Bouteillier U. New fundamental resistance exercise
determinants of molecular and cellular muscle adaptations.
Eur J Appl Physiol 2006; 97: 643-63.
43. Mitsiopoulos N, Baumgartner RN, Heymsfield SB, et al. Ca-
daver validaton of skeletal muscle measurement by magnetic
resonance imaging and computerized tomography. J Appl
Physiol 1998; 85(1): 115-22.
44. Reeves ND, Maganaris CN, Narici M. Ultrasonographic
assessment of human skeletal muscle size. Eur J Appl Physiol
2004; 91: 116-8.
45. Sanada K, Kearns CF, Midorikawa T, et al. Prediction and
validation of total and regional skeletal muscle mass by ultra-
sound in Japanese adults. Eur J Appl Physiol 2006; 96: 24-31.
46. Fry AC. The role of resistance exercise intensity on muscle
fibre adaptations. Sports Med 2004; 34(10): 663-79.
47. Bird SP, Tarpenning KM, Marino FE. Designing Resistance
training programmes to enhance muscular fitness. Sports Med
2005; 35(10): 841-51.
48. Blazevich AJ. Effects of physical training and detraining, im-
mobilisation, growth and aging on human fascicle geometry.
Sports Med 2006; 36(12): 1003-17.
49. Folland JP, Williams AG. The adaptations to strength training:
Morphological and neurological contributions to increased
strength. Sports Med 2007; 37(2): 145-68.
50. Roig M, O’Brien K, Kirk G, et al. The effects of eccentric versus
concentric resistance training on muscle strength and mass
in healthy adults: asystematic review with meta-analysis. Br
J Sports Med 2008; 43: 556-68.
51. Anderson JL, Aagaard P. Effects of strength training on
muscle fiber types and size; consequences for athletes tra-
ining for high-intensity sport. Scand J Med Sci Sports 2010;
20(Suppl.2): 32-8.
52. van WesselT, de Haan, A, van der Laarse WJ, et al. The muscle
fiber type-fiber size paradox: hypertrophy or oxidative me-
tabolism? Eur J Appl Physiol 2010; 110: 665-94.
53. Loenneke JP. Skeletal muscle hypertrophy: How importance
is exercise intensity? J Tra ino l 2012; 1: 28-31.
54. Yasuda T, Brechue WF, Fujita T, et al. Muscle activation during
low-intensity muscle contractions with restricted blood flow.
J Sport Sci 2009; 27(5): 479-89.
55. Häkkinen K, Kallinen M. Distribution of strength training
volume into one or two daily sessions and neuromuscular
adaptations in female athletes. Electromyogr Clin Neurophysiol
1994; 34: 117-24.
56. Häkkinen K, Kallinen M, Pastinen U-M, et al. Neuromuscular
adaptations during bilateral versus unilateral strength training
in middle-aged and elderly men and women. Acta Physiol
Scan 1996; 158: 77-88.
57. Häkkinen K, Pakarinen A, Kraemer WJ, et al. Basal concen-
trations and acute responses of serum hormones and strength
development during heavy resistance training in middle-aged
and elderly men and women. J Gerontol ABiol Sci Med 2000;
55(2): B95-105.
58. Häkkinen K, Alen M, Kraemer WJ, et al. Neuromuscular ada-
ptations during concurrent strength and endurance training
versus strength training. Eur J Appl Physiol 2003; 89: 42-52.
59. Ahtiainen JP, Pakarinen A, Alen M, et al. Muscle hypertrophy,
hormonal adaptations and strength development during
strength training in strength-trained and untrained men. Eur
J Appl Physiol 2003; 89: 555-63.
60. Fisher J. Acritical commentary on the practical application of
resistance training studies. J Trainology 2013; 2: 10-2.
61. Fisher J, Steele J, Bruce-Low S, Smith D. Evidence-Based
Resistance Training Recommendations. Med Spor t 2011;
15(3): 147-62.
62. Carpinelli RN. The size principle and acritical analysis of
the unsubstantiated heavier-is-better recommendation for
resistance training. J Exerc Sci Fit 2008; 6(2): 67-86.
63. Ruther CL, Golden CL, Harris RT, et al. Hypertrophy, resist-Hypertrophy, resist-
ance training, and the nature of skeletal muscle activation. J
Strength Cond Res 1995; 9(3): 155-9.
64. Gondin, J, Guette M, Ballay Y, et al. Electromyostimulation
training effects on neural drive and muscle architecture. Med
Sci Sports Exerc 2005; 37(8): 1291-9.
65. Goto K, Nagasawa M, Yanagisawa O, et al. Muscular adapta-Muscular adapta-
tions to combinations of high- and low-intensity resistance
exercises. J Strength Cond Res 2004; 18(4): 730-7.
66. Goto K, Ishii N, Kizuka T, et al. The impact of metabolic stress
on hormonal responses and muscular adaptations. Med Sci
Sports Exerc 2005; 37(6): 955-63.
67. Hisaeda H, Miyagawa K, Kuno SY, et al. Influence of two
different modes of resistance training in female subjects.
Ergonomics 1996; 39(6): 842-52.
68. Kraemer WJ, Nindl BC, Ratamess NA, et al. Changes in
muscle hypertrophy in women with periodised resistance
training. Med Sci Sports Exerc 2004; 36(4): 697-708.
69. PopovDV,SwirkunDV, NetrebaAI,etal.Hormonalada-
ptation determines the increase in muscle mass and strength
during low-intensity strength training without relaxation.
Human Physiology 2006; 32(5): 609-14.
70. Tanimoto M, Ishii, N. Effects of low-intensity resistance exer-
cise with slow movement tonic force generation on muscular
function in young men. J Appl Physiol 2006; 100: 1150-7.
71. Tanimoto M, Sanada K, Yamamoto K, et al. Effects of whole
body low-intensity resistance training with slow movement
and tonic force generation on muscular size and strength in
young men. J Strength Cond Res 2008; 22(6): 1926-38.
234
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
72. Ogasawara R, Loenneke JP, Thiebaud RS, et al. Low-load
bench press training to fatigue results in muscle hypertrophy
similar to high-load bench press training. Int J Clin Med
2013; 4: 114-21.
73. Léger B, Cartoni R, Praz M, et al. Akt signalling through GSK-
3β, mTOR and Foxo1 is involved in human skeletal muscle
hypertrophy and atrophy. J Physiol 2006; 576(3): 923-33.
74. De Souza Jr TP, Fleck SJ, Simao R, et al. Comparison between
constant and decreasing rest intervals: Influence on maximal
strength and hypertrophy. J Strength Cond Res 2010; 24(7):
1843-50.
75. Bruce-Low S, Smith D. Explosive exercise in sports training:
acritical review. J Exerc Physiol 2007; 10: 21-33.
76. Carpinelli, R, Otto RM, Winett RA. Acritical analysis of the
ACSM position stand on resistance training: insufficient
evidence to support recommended protocols. J Exerc Physiol
2004; 7: 1-60.
77. Fisher J, Smith D. Attempting to better define “intensity”
for muscular performance: is it all wasted effort? Eur J Appl
Physiol 2012; IN PRESS.
78. Young WB, Bibby GE. The effect of boluntary effort to in-
fluence speed of contraction on strength, muscular power,
and hypertrophy development. J Strength Cond Res 1993;
7(3): 172-8.
79. Friedmann B, Kinscherf R, Borisch S, et al. Effects of low-
-resistance/high repetition strength training in hypoxia on
muscle structure and gene expression. Pflugers Arch – Eur J
Physiol 2003; 446: 742-51.
80. FriedmannB,KinscherfR,VorwaldS,etal.Muscularadap-Muscular adap-
tations to computer-guided strength training with eccentric
overload. Acta Physiol Scand 2004; 182: 77-88.
81. SeynnesOR, de Boer M, Narici MV.Earlyskeletalmuscle
hypertrophy and architectural changes in response to high-
-intensity resistance training. J Appl Physiol 2007; 102: 368-73.
82. Ogasawara R, Thiebaud RS, Loenneke JP, et al. Time course
for arm and chest muscle thickness changes following bench
press training. Interventional Med Appl Sci 2012; 4(4): 217-20.
83. Ahtiainen JP, Pakarinen A, Alen M, et al. Short vs. long rest
period between the sets in hypertrophic resistance training:
influence on muscle strength, size, and hormonal adaptations
in trained men. J Strength Cond Res 2005; 19(3): 572-82.
84. Starkey DB, Pollock ML, Ishida Y, et al. Effect of resistance
training volume on strength and muscle thickness. Med Sci
Sports Exerc 1996; 28(10): 1311-20.
85. Ostrowski KJ, Wilson GJ, Weatherby R, et al. The effect of
weight training volume on hormonal output and muscular
size and function. J Strength Cond Res 1997; 11(1):148-54.
86. BottaroM,VelosoJ,WagnerD,etal.Resistancetrainingfor
strength and muscle thickness: Effect of number of sets and
muscle group trained. Sci Sports 2011; 26: 259-64.
87. Sooneste H, Tanimoto M, Kakigi R, et al. Effects of training
volume on strength and hypertrophy in young men. J Strength
Cond Res 2012; 27(1): 8-13.
88. Gentil P, Soares SRS, Pereira MC, et al. Effect of adding single-
-joint exercises to amulti-joint exercise resistance-training
program on strength and hypertrophy in untrained subjects.
Appl Physiol Nutr Metab 2013; 38: 341-4.
89. McCarthy JP, Pozniak MA, Agre JC. Neuromuscular adapta-Neuromuscular adapta-
tions to concurrent strength and endurance training. Med Sci
Sports Exerc 2002; 34(3): 511-9.
90. Izquierdo M, Häkkinen K, Ibáñez J, et al. Effects of combined
resistance and cardiovascular training on strength, power,
muscle cross-sectional area, and endurance markers in middle
aged me. Eur J Appl Physiol 2005; 94: 70-5.
91. Izquierdo M, Ibáñez J, Häkkinen K, et al. Once weekly com-
bined resistance and cardiovascular training in healthy older
men. Med Sci Sports Exerc 2004; 36(3): 435-43.
92. Lundberg TR, Fernandez-Gonzalo R, Gustafsson T, et al.
Aerobic exercise does not compromise muscle hypertrophy
response to short-term resistance training. J Appl Physiol
2013; 114: 81-9.
93. Norrbrand L, Fluckey JD, Pozzo M, et al. Resistance training
using eccentric overload induces early adaptations in skeletal
muscle size. Eur J Appl Physiol 2008; 102: 271-81.
94. Pinto RS, Gomes N, Radaelli R, et al. Effect of range of mo-Effect of range of mo-
tion on muscle strength and thickness. J Strength Cond Res
2012; 26(8): 2140-5.
95. Eugene McMahon G, Onambélé-Pearson G. Impact of range
of motion during ecologically valid resistance training proto-
cols, on muscle size, subcutaneous fat and strength. J Strength
Cond Res 2013; IN PRESS.
96. Moritani T, Muramatsu S, Muro M. Activity of motor units
during concentric and eccentric contractions. Am J Phys Med
1987; 66(6): 338-50.
97. Blazevich AJ, Cannavan D, Coleman DR, et al. Influence of
concentric and eccentric resistance training on architectural
adaptation in human quadriceps muscles. J Appl Physiol 2007;
103: 1565-75.
98. Moore DR, Young M, Phillips SM. Similar increases in muscle
size and strength in young men after training with maximal
shortening or lengthening contractions when matched for
total work. Eur J Appl Physiol 2012; 112: 1587-92.
99. Higbie EJ, Cureton KJ, Warren III GL, et al. Effects of con-
centric and eccentric training on muscle strength, cross-
-sectional area, and neural activation. J Appl Physiol 1996;
81(5): 2173-81.
100. Farthing JP, Chilibeck PD. The effects of eccentric and con-
centric training at different velocities on muscle hypertrophy.
Eur J Appl Physiol 2003; 89: 578-86.
101. Housh DJ, Housh TJ, Weir JP, et al. Effects of unilateral
concentric-only dynamic constant external resistance training
on quadriceps femoris cross-sectional area. J Strength Cond
Res 1998a; 12(3): 185-91.
102. Housh DJ, Housh TJ, Weir JP, et al. Effects of unilateral
eccentric-only dynamic constant external resistance training
on quadriceps femoris cross-sectional area. J Strength Cond
Res 1998b; 12(3): 192-8.
103. Smith RC, Rutherford OM. The role of metabolites in strength
training. Eur J Appl Physiol 1995; 71: 332-6.
104. Walker PM, Brunotte F, Rouhier-Marcer I, et al. Nuclear
magnetic resonance evidence of different muscular adapta-
tions after resistance training. Arch Phys Med Rehabil 1998;
79: 1391-8.
105. Brandenburg JP, Docherty D. The effects of accentuated ec-
centric loading on strength, muscle hypertrophy, and neural
adaptations in trained individuals. J Strength Cond Res 2002;
16(1): 25-32.
106. Jones DA, Rutherford OM. Human muscle strength training:
the effects of three different regimes and the nature of the
resultant changes. J Physiol 1987; 391: 1-11.
107. Garfinkel S, Cafarelli E. Relative changes in maximal force,
EMG, and muscle cross-sectional area after isometric training.
Med Sci Sports Exerc 1992; 24(11): 1220-7.
108. Kubo K, Kanehisa H, Fukunaga T. Effects of different dura-
tion isometric contractions on tendon elasticity in human
quadriceps muscles. J Physiol 2001; 536(2): 649-55.
109. Ikai M, Fukunaga T. Astudy on training effect on strength
per unit cross-sectional area of muscle by means of ultrasonic
measurement. Int ZAngew Physiol 1970; 28: 173-80.
110. Davies J, Parker DF, Rutherford OM, et al. Changes in
strength and cross sectional area of the elbow flexors as
aresult of isometric strength training. Eur J Appl Physiol
1988; 57: 667-70.
111. Tesch PA, Ekberg A, Lindquist DM, et al. Muscle hypertrophy
following 5-week resistance training using anon-gravity-de-
pendent exercise system. Acta Physiol Scand 2004a; 180: 89-98.
112. Tesch PA, Trieschmann JT, Ekberg A. Hypertrophy of chroni-
cally unloaded muscle subjected to resistance exercise. J Appl
Physiol 2004b; 96: 1451-8.
113. O’Hagan FT, Sale DG, MacDougall JD, et al. Comparative ef-
fectiveness of accommodating and weight resistance training
modes. Med Sci Sports Exerc 1995; 27(8): 1210-9.
114. NariciMV,HoppelerH,KayserB,etal.Humanquadriceps
cross-sectional area, torque and neural activation during 6
months strength training. Acta Physiol Scan 1996; 157: 175-86.
115. Abe T, Kojima K, Kearns CF, et a l. Whole body muscle hyper-
trophy from resistance training: distribution and total mass.
Br J Sports Med 2003;37: 543-5.
235
Fisher J., Steele J., Smith D. / Medicina Sportiva 17 (4): 217-235, 2013
Authors’ contribution
A – Study Design
B – Data Collection
C – Statistical Analysis
D – Data Interpretation
E – Manuscript Preparation
F – Literature Search
G – Funds Collection
116. Matta T, Simao R, Freitas de Salles B, et al. Strength training’s
chronic effects on muscle architecture parameters of different
arm sites. J Strength Cond Res 2011; 25(6): 1711-7.
117. Wakahara T, Miyamoto N, Sugisaki N, et al. Association
between regional differences in muscle activation in one ses-
sion of resistance exercise and in muscle hypertrophy after
resistance training. Eur J Appl Physiol 2012;112: 1569-76.
118. Wakahara T, Fukutani A, Kawakami Y, et al. Nonuniform
muscle hypertrophy: Its relation to muscle activation in train-
ing session. Med Sci Sports Exerc 2013; 45(11): 2158-65. doi:
10.1249/MSS.0b013e3182995349
119. Hedayatpour N, Falla D. Non-uniform muscle adaptations to
eccentric exercise and the implications for training and sport.
J Electromyogr Kinesiol 2012; 22: 329-33.
120. Ivey FM, Roth SM, Ferrell RE, et al. Effects of age, gender,
and myostatin genotype on the hypertrophic response to
heavy resistance strength training. J Gerontol Med Sci 2000;
55(11): M641-748.
121. Kawakami Y, Abe T, Kuno SY, et al. training-induced changes
in muscle architecture and specific tension. Eur J Appl Physiol
1995; 72: 37-43.
122. Young A, Stokes M, Round JM, et al. The effect of high-
-resistance training on the strength and cross-sectional area
of the human quadriceps. Eur J Clin Invest 1983; 13: 411-7.
123. NariciMV,RoiGS,LandoniL,etal.Changes in force, cross-
sectional area and neural activation during strength training
and detraining of the human quadriceps. Eur J Appl Physiol
1989; 59: 310-9.
124. Ploutz LL, Tesch PA, Biro RL, et al. Effect of resistance train-Effect of resistance train-
ing on muscle use during exercise. J Appl Physiol 1994; 76(4):
1675-81.
125. Hubal MJ, Gordish-Dressman H, Thompson PD, et al.
Variabilityin musclesizeandstrengthgain afterunilateral
resistance training. Med Sci Sports Exerc 2005; 37(6): 964-72.
126. AbeT, DeHoyosDV,PollockML, et al. Time course for
strength and muscle thickness changes following upper and
lower body resistance training in men and women. Eur J Appl
Physiol 2000; 81: 174-80.
127. Lehman GJ. The influence of grip width and forearm prona-
tion/supination on upper body myoelectric activity during
the flat bench press. J Strength Cond Res 2005; 19(3): 587-91.
128. Ogasawara R, Yasuda T, Sakamaki M, et al. Effects of periodic
and continued resistance training on muscle CSA and strength
in previously untrained men. Clin Physiol Funct Imaging
2011; 31: 399-404.
129. Ogasawara R, Yasuda T, Ishii N, et al. Comparison of muscle
hypertrophy following 6-month of continuous and periodic
strength training. Eur J Appl Physiol 2013; 113: 975-85.
130. Jones DA, Rutherford OM. Human muscle strength training:
the effects of three different regimes and the nature of the
resultant changes. J Physiol 1987; 391: 1-11.
131. Lemon PWR, Tarnopolsky MA, MacDougall JD, et al. Protein
requirements and muscle mass/strength changes during in-
tensive training in novice bodybuilders. J Appl Physiol 1992;
73(2): 767-75.
Accepted: November 28, 2013
Published: December 20, 2013
Address for correspondence:
James Fisher
Department of Health, Exercise and Sport Science
Southampton Solent University
East Park Terrace
Southampton SO14 0YN
UK
Tel. +44 2380 319163
E-mail: james.fisher@solent.ac.uk
James Steele: James.Steele@solent.ac.uk
Dave Smith: D.D.Smith@mmu.ac.uk
... According to Henneman's size principle, motor units are recruited in an orderly fashion. 1 This principle dictates that as force production requirements increase, motor units are recruited according to the magnitude of their force output, with small motor units being recruited first. 2 Theoretically, in a resistance exercise set using moderate loads, lower threshold motor units associated with Type I muscle fibres are initially recruited to lift the load. [2][3][4] As the lower threshold motor units become fatigued, increased recruitment occurs of the higher threshold motor units associated with Type II muscle fibres in order to maintain force production. [2][3][4] Therefore, performing resistance exercise sets to momentary muscular failure (i.e. the maximum number of possible repetitions in a given set) is thought to be necessary to recruit all possible motor units. ...
... [2][3][4] As the lower threshold motor units become fatigued, increased recruitment occurs of the higher threshold motor units associated with Type II muscle fibres in order to maintain force production. [2][3][4] Therefore, performing resistance exercise sets to momentary muscular failure (i.e. the maximum number of possible repetitions in a given set) is thought to be necessary to recruit all possible motor units. 3,4 Accordingly, some suggest this manner of training is optimal for achieving resistance training-induced increases in muscular strength and muscle size. ...
... [2][3][4] Therefore, performing resistance exercise sets to momentary muscular failure (i.e. the maximum number of possible repetitions in a given set) is thought to be necessary to recruit all possible motor units. 3,4 Accordingly, some suggest this manner of training is optimal for achieving resistance training-induced increases in muscular strength and muscle size. 3,4 Given the hypothesis that training to muscle failure is important for catalyzing resistance training-induced adaptations, several studies examined the effects that this type of training has on muscular strength and hypertrophy, as compared to the effects of training that does not include reaching muscle failure. ...
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Objective We aimed to perform a systematic review and meta-analysis of the effects of training to muscle failure or non-failure on muscular strength and hypertrophy. Methods Meta-analyses of effect sizes (ESs) explored the effects of training to failure vs. non-failure on strength and hypertrophy. Subgroup meta-analyses explored potential moderating effects of variables such as training status (trained vs. untrained), training volume (volume equated vs. non-equated), body region (upper vs. lower), exercise selection (multi- vs. single-joint exercises (only for strength)), and study design (independent vs. dependent groups). Results Fifteen studies were included in the review. All studies included young adults as participants. Meta-analysis indicated no significant difference between the training conditions for muscular strength (ES = –0.09; 95% confidence interval (CI): –0.22 to 0.05) and for hypertrophy (ES = 0.22; 95%CI: –0.11 to 0.55). Subgroup analyses that stratified the studies according to body region, exercise selection, or study design showed no significant differences between training conditions. In studies that did not equate training volume between the groups, the analysis showed significant favouring of non-failure training on strength gains (ES = –0.32; 95%CI: –0.57 to –0.07). In the subgroup analysis for resistance-trained individuals, the analysis showed a significant effect of training to failure for muscle hypertrophy (ES = 0.15; 95%CI: 0.03 to 0.26). Conclusion Training to muscle failure does not seem to be required for gains in strength and muscle size. However, training in this manner does not seem to have detrimental effects on these adaptations, either. More studies should be conducted among older adults and highly trained individuals to improve the generalizability of these findings.
... Kojić et al. [62] highlighted no difference in bicep brachii muscle mass gain for 1 and 4 s eccentric despite the 4 s group achieving significantly greater eccentric TUT, even though the 1 s group performed significantly greater concentric TUT, which has been shown to increase CSA [51,82] (Table 5). In conjunction with this, the review by Fisher and Steele [87] found no significant correlation between repetition duration and muscular hypertrophy. This was further supported by Schoenfeld et al. [88], who found no distinct difference between 0.8 and 8 s of total repetition duration with respect to muscle hypertrophy and stated that eccentric durations should range from 2 to 4 s. ...
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Eccentric training as a method to enhance athletic performance is a topic of increasing interest to both practitioners and researchers. However, data regarding the effects of performing the eccentric actions of an exercise at increased velocities are limited. This narrative review aimed to provide greater clarity for eccentric methods and classification with regard to temporal phases of exercises. Between March and April 2021, we used key terms to search the PubMed, SPORTDiscus, and Google Scholar databases within the years 1950–2021. Search terms included ‘fast eccentric’, ‘fast velocity eccentric’, ‘dynamic eccentric’, ‘accentuated eccentric loading’, and ‘isokinetic eccentric’, analysing both the acute and the chronic effects of accelerated eccentric training in human participants. Review of the 26 studies that met the inclusion criteria identified that completing eccentric tempos of < 2 s increased subsequent concentric one repetition maximum performance, velocity, and power compared with > 4 s tempos. Tempos of > 4 s duration increased time under tension (TUT), whereas reduced tempos allowed for greater volume to be completed. Greater TUT led to larger accumulation of blood lactate, growth hormone, and testosterone when volume was matched to that of the reduced tempos. Overall, evidence supports eccentric actions of < 2 s duration to improve subsequent concentric performance. There is no clear difference between using eccentric tempos of 2–6 s if the aim is to increase hypertrophic response and strength. Future research should analyse the performance of eccentric actions at greater velocities or reduced time durations to determine more factors such as strength response. Tempo studies should aim to complete the same TUT for protocols to determine measures for hypertrophic response.
... 3,4 Thus, many have sought to identify how the manipulation of resistance training variables might lead to -optimal‖ adaptations in such outcomes, as evidenced by repeated attempts over recent decades to review the literature and provide consensus statements on this topic. [5][6][7][8][9][10] One variable that is often hotly debated within resistance training is training to failure. The present opinion piece presents a narrative based upon 2 recent systematic reviews and meta-analyses that ask, and propose to answer, the question: -To optimize adaptations, should I train to momentary failure or not?‖ 11,12 For this piece, momentary failure is defined as the point trainees reach where -despite attempting to do so they cannot complete the concentric portion of their current repetition without deviation from the prescribed form of the exercise‖. ...
... With respect to hypertrophy, an early narrative review by Fisher et al. (219) argued that evidence did not support the contention that adaptation was attenuated because of concurrent training. However, the first meta-analysis of this topic from Wilson et al. (220) suggested that there was indeed evidence of an 'interference' effect. ...
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Hypertrophy can be operationally defined as an increase in the axial cross-sectional area of a muscle fiber or whole muscle, and is due to increases in the size of pre-existing muscle fibers. Hypertrophy is a desired outcome in many sports. For some athletes, muscular bulk and, conceivably, the accompanying increase in strength/power, are desirable attributes for optimal performance. Moreover, bodybuilders and other physique athletes are judged in part on their muscular size, with placings predicated on the overall magnitude of lean mass. In some cases, even relatively small improvements in hypertrophy might be the difference between winning and losing in competition for these athletes. This position stand of leading experts in the field synthesizes the current body of research to provide guidelines for maximizing skeletal muscle hypertrophy in an athletic population. The recommendations represent a consensus of a consortium of experts in the field, based on the best available current evidence. Specific sections of the paper are devoted to elucidating the constructs of hypertrophy, reconciliation of acute vs long-term evidence, and the relationship between strength and hypertrophy to provide context to our recommendations.
... Improvements in muscle morphofunction seem to be related to patterns of motor unit activation during the exercise. Some authors report that greater hypertrophy can be obtained with higher recruitment of motor units (Fisher et al. 2013), as well as greater strength gains (Schoenfeld et al. 2017). Others state that muscle hypertrophy cannot be predicted by acute surface electromyography (sEMG) measures, since similar gains in hypertrophy have been observed with RT with low and high loads (Schoenfeld et al. 2017), whereas higher sEMG-RMS have been observed in resistance exercises with high loads (Schoenfeld et al. 2014). ...
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The aim of the present study was to investigate the influence of intensity of load and cuff pressure on training volume and myoelectric activation during the knee extension exercise executed with and without blood flow restriction (BFR) to failure. Ten young men (22 ± 2 y), with at least six months of training experience, visited the laboratory on eight non-consecutive days with intervals of at least 48 hours between sessions. In the first two visits, one-repetition maximum (1RM) test and retest were performed in the unilateral knee extension exercise. In the subsequent six visits, the subjects performed resistance training sessions (4 sets to concentric failure) at different load intensities (30, or 40% of 1RM) and BFR pressures (0, 100, or 150mmHg). The restriction cuff was of 18-cm width and was positioned on the superior 1/3 of the thigh. Measures of training volume, and myoelectric activity from the vastus lateralis and vastus medialis via surface electromyographic, were recorded. During experimental sessions, it was observed that the use of BFR significantly reduced the training volume, independently of the load used. Less repetitions were performed with a restriction pressure of 150mmHg (47 ± 10) compared to 0mmHg (61 ± 15) and 100mmHg (59 ± 17), and with 30%1RM (50 ± 14) compared to 40%1RM (61 ± 15). For surface electromyography measures, no significant differences were observed between the conditions (P>0.05). In conclusion, the application of BFR to low-load knee extension exercise to failure led to lower training volume but did not influence myoelectric activity.
... Resistance training programs represent benefits such as recovering metabolism after fatigue due to daily chores as well as providing a healthy and long life for sedentary individuals, reducing the period for rest, increasing metabolic rate, providing bone mineral density, and reducing pain (Fisher, Steele, Bruce-Low, & Smith, 2011). Resistance (strength) workouts are considered to be an inevitable part of exercise programs in achieving these objectives (ACSM, 2002). ...
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This study aimed to analyze the effects of an 8-week training with the elastic resistance bands on body composition and postural control in sedentary women. Thirty-four female sedentary university students participated in the study based on voluntariness. The subjects were randomly divided into two groups: The experimental group and the control group. The experimental group performed an 8-week elastic resistance band training. Body composition measurements included the body weight, body mass index, body fat percentage, skinfold thicknesses, and circumferences. The Overall Stability Index and limit of stability were measured to evaluate postural performance using the Biodex Balance System. The overall stability index scores were evaluated for two conditions: Eye-open and eye-closed. After the training, body weight, the circumferences of waist, upper arm, and calf significantly increased (p<0.05) although there was no change in the circumferences of the hip, thigh, shoulder, and chest (p>0.05). The skinfold thicknesses and body fat percentage decreased in the experimental group (p<0.05). The training caused the overall stability index scores to reduce in eye-open and eye-closed conditions. There was no significant difference in the limit of stability scores (p>0.05). In conclusion, these results show that elastic resistance band exercise could increase postural control and body composition in sedentary women. Also, the results suggest that the training might lower sedentary women's body fat by increasing muscle mass. Bu çalışma sedanter kadınlarda 8 haftalık elastik direnç bantları ile yapılan antrenmanın vücut kompozisyonu ve postüral kontrol üzerindeki etkilerini incelemeyi amaçlamıştır. Araştırmaya gönüllülük esasına göre üniversite öğrencisi olan 34 sedanter kadın katılmıştır. Katılımcılar rastgele iki gruba ayrılmıştır: Deney Grubu ve Kontrol Grubu. Deney grubu, 8 haftalık bir elastik direnç bant antrenmanına katılmışlardır. Vücut kompozisyonunu belirlemek için vücut ağırlığı, vücut kitle indeksi, vücut yağ yüzdesi, deri kıvrım kalınlıkları ve çevre ölçümleri gerçekleştirildi. Postüral kontrolü değerlendirmek için Biodex Denge Sistemi kullanılarak genel stabilite indeksi ve stabilite sınırları ölçülmüştür. Genel stabilite indeksi skorları iki koşulda değerlendirilmiştir: Göz açık ve göz kapalı. Antrenman sonrası vücut ağırlığı, bel, üst kol ve baldır çevresi önemli ölçüde artmıştır (p<0,05), ancak kalça, uyluk, omuz ve göğüs çevresinde değişiklik gözlemlenmedi (p>0,05). Deney grubunda deri kıvrım kalınlıkları ve vücut yağ yüzdesi azaldı (p<0,05). Elastik direnç bant antrenmanı, gözler açık ve gözler kapalı koşullarda genel stabilite indeksi puanlarının düşmesine neden oldu. Sanılım sınırları skorlarında anlamlı bir farklılık yoktu (p>0,05). Bu sonuçlar, elastik direnç bant antrenmanlarının sedanter kadınların postüral kontrolünü ve vücut kompozisyonunu artırabileceğini göstermektedir. Ayrıca sonuçlar, elastik direnç bantları ile uygulanan antrenmanların kas kütlesini artırarak sedanter kadınların vücut yağ yüzdesini azaltabileceğini göstermiştir.
... These strength improvements are in line with previous literature (Conlon et al., 2016) and are expected to have an impact on reducing the risk of injury from falls; maintaining functional independence for a greater period of time; and improving quality of life as it allows individuals to perform activities of daily living easier (Schaap et al., 2013;Trombetti et al., 2016). The shared benefits might be explained by the prescription exercise sets to the momentary muscular failure in both groups, conferring greater adaptations in strength and hypertrophy compared to other methods (Fisher et al., 2013). ...
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... Current recommendations from organizations such as the American College of Sports Medicine give detailed advice for the number of sessions per week, repetitions, rest periods, and the load lifted (expressed as 1-repetition maximum [1RM]) (82). However, not only has the evidence supporting these recommendations recently been challenged (83), but our opinion is that the complex nature of these recommendations is a barrier to people taking part in such exercise, alongside their focus on exercises that must be performed in a gym facility (ie, by recommending loads based on 1RM, which can only be measured on gym equipment). Indeed, counter to most recommendations, which suggest that a relatively high load is required for gains in muscle mass and strength, recent advances indicate that the load at which the exercise is performed does not determine the magnitude of the effects of resistance exercise on muscle, when exercise is performed to voluntary failure, with the majority of benefit coming from a single set of exercise performed per week (84-86, 87, 88). ...
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... Moreover, increases in muscle size are commonly pursued with aesthetic or competitive purposes, like in bodybuilding. resistance training (rt) is considered one of the most effective exercise-based strategies to promote muscle hypertrophy and increases in lean body mass [7,8]. the achievement of optimum results from rt seems to be dependent on the manipulation and combination of several variables involved in its prescription (e.g. ...
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