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The Influence of Frequency, Intensity, Volume and Mode of Strength Training on Whole Muscle Cross-Sectional Area in Humans

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Strength training is an important component in sports training and rehabilitation. Quantification of the dose-response relationships between training variables and the outcome is fundamental for the proper prescription of resistance training. The purpose of this comprehensive review was to identify dose-response relationships for the development of muscle hypertrophy by calculating the magnitudes and rates of increases in muscle cross-sectional area induced by varying levels of frequency, intensity and volume, as well as by different modes of strength training. Computer searches in the databases MEDLINE, SportDiscus® and CJNAHL® were performed as well as hand searches of relevant journals, books and reference lists. The analysis was limited to the quadriceps femoris and the elbow flexors, since these were the only muscle groups that allowed for evaluations of dose-response trends. The modes of strength training were classified as dynamic external resistance (including free weights and weight machines), accommodating resistance (e.g. isokinetic and semi-isokinetic devices) and isometric resistance. The subcategories related to the types of muscle actions used. The results demonstrate that given sufficient frequency, intensity and volume of work, all three types of muscle actions can induce significant hypertrophy at an impressive rate and that, at present, there is insufficient evidence for the superiority of any mode and/or type of muscle action over other modes and types of training. Tentative dose-response relationships for each variable are outlined, based on the available evidence, and interactions between variables are discussed. In addition, recommendations for training and suggestions for further research are given.
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Sports Med 2007; 37 (3): 225-264
R
EVIEW
A
RTICLE
0112-1642/07/0003-0225/$44.95/0
2007 Adis Data Information BV. All rights reserved.
The Influence of Frequency, Intensity,
Volume and Mode of Strength
Training on Whole Muscle
Cross-Sectional Area in Humans
Mathias Wernbom,
1
Jesper Augustsson
1,2
and Roland Thome
´
e
1,2
1 Lundberg Laboratory for Human Muscle Function and Movement Analysis, Department of
Orthopaedics, Sahlgrenska University Hospital, G
¨
oteborg University, G
¨
oteborg, Sweden
2 SportRehab Physical Therapy and Sports Medicine Clinic, G
¨
oteborg, Sweden
Contents
Abstract ....................................................................................226
1. Methods ................................................................................227
1.1 Literature Search ....................................................................227
1.2 Classification of Muscle Actions, Training Methods and Modalities ........................228
1.3 Quantification of Exercise Frequency, Intensity and Volume ..............................229
1.4 Classification of Training Status ........................................................230
1.5 Calculation of Changes and Rate of Changes in Muscle Cross-Sectional Area (CSA) .......230
2. Results Part 1: Quadriceps Studies .........................................................231
2.1 Quadriceps Studies: Dynamic External Resistance .......................................231
2.1.1 Length of Training Period, Average Increase in CSA and CSA Per Day ...............232
2.1.2 Rate of Gain in CSA: Men versus Women .........................................232
2.1.3 Frequency ....................................................................232
2.1.4 Intensity .......................................................................232
2.1.5 Volume .......................................................................232
2.2 Quadriceps Studies: Accommodating Resistance .......................................233
2.2.1 Length of Training Period, Average Increase in CSA and CSA Per Day ...............233
2.2.2 Frequency ....................................................................233
2.2.3 Velocity .......................................................................234
2.2.4 Torque ........................................................................234
2.2.5 Volume .......................................................................234
2.2.6 Total Duration Per Session .......................................................235
2.2.7 Time-Torque Product Per Session .................................................235
2.3 Quadriceps Studies: Isometric Resistance...............................................235
2.3.1 Length of Training Period, Average Increase in CSA and CSA Per Day ...............235
2.3.2 Frequency ....................................................................235
2.3.3 Intensity .......................................................................235
2.3.4 Volume .......................................................................235
2.4 Quadriceps Studies: Combined Strength and Endurance Training ........................236
2.4.1 Rate of Gain in CSA: Combined Training versus Pure Strength Training ...............236
2.4.2 Length of Training Period and Increase in CSA ....................................236
2.5 Quadriceps Studies: All Voluntary Training Modes .......................................236
2.5.1 Length of Training Period and Increase in CSA ....................................236
2.6 Quadriceps Studies: Strength Training as a Countermeasure During Unloading .............236
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226 Wernbom et al.
2.6.1 Unloading versus Unloading and Exercise Countermeasure ........................236
2.7 Quadriceps Studies: Electromyostimulation .............................................237
3. Results Part 2: Elbow Flexor Studies .........................................................237
3.1 Elbow Flexor Studies: Dynamic External Resistance ......................................237
3.1.1 Length of Training Period, Average Increase in CSA and CSA Per Day ...............238
3.1.2 Frequency ....................................................................238
3.1.3 Intensity .......................................................................238
3.1.4 Volume .......................................................................238
3.2 Elbow Flexor Studies: Accommodating Resistance ......................................239
3.3 Elbow Flexor Studies: Isometric Resistance ..............................................239
4. Discussion ...............................................................................239
4.1 Frequency ..........................................................................239
4.2 Intensity .............................................................................242
4.3 Volume .............................................................................244
4.4 Mode of Training and Type of Muscle Action ...........................................245
4.5 Rest Periods and the Role of Fatigue ...................................................247
4.6 Interactions Between Frequency, Intensity, Volume and Mode ...........................249
4.7 Time Course of Muscle Hypertrophy ...................................................251
4.8 Hypertrophic Response of the Quadriceps versus the Elbow Flexors .......................252
4.9 The Stimulus for Muscle Hypertrophy in Strength Training .................................253
4.10 Suggestions for Future Research ......................................................254
4.11 Limitations .........................................................................256
4.12 Training Implications and Recommendations ..........................................257
5. Conclusions .............................................................................258
Strength training is an important component in sports training and rehabilita-
Abstract
tion. Quantification of the dose-response relationships between training variables
and the outcome is fundamental for the proper prescription of resistance training.
The purpose of this comprehensive review was to identify dose-response relation-
ships for the development of muscle hypertrophy by calculating the magnitudes
and rates of increases in muscle cross-sectional area induced by varying levels of
frequency, intensity and volume, as well as by different modes of strength
training.
Computer searches in the databases MEDLINE, SportDiscus
and CINAHL
were performed as well as hand searches of relevant journals, books and reference
lists. The analysis was limited to the quadriceps femoris and the elbow flexors,
since these were the only muscle groups that allowed for evaluations of dose-
response trends. The modes of strength training were classified as dynamic
external resistance (including free weights and weight machines), accommodating
resistance (e.g. isokinetic and semi-isokinetic devices) and isometric resistance.
The subcategories related to the types of muscle actions used. The results
demonstrate that given sufficient frequency, intensity and volume of work, all
three types of muscle actions can induce significant hypertrophy at an impressive
rate and that, at present, there is insufficient evidence for the superiority of any
mode and/or type of muscle action over other modes and types of training.
Tentative dose-response relationships for each variable are outlined, based on the
available evidence, and interactions between variables are discussed. In addition,
recommendations for training and suggestions for further research are given.
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
Strength Training and Muscle Cross-Sectional Area 227
Strength training has become increasingly popu- training periods or training sessions aimed at stimu-
lating maximum hypertrophy by high volume and
lar in recent decades. Whereas previously strength
moderate loads are followed by periods or sessions
training had been used by a few selected athletes to
aimed at increasing maximum strength by moderate
improve their strength and size, it is now an impor-
volume and heavy loads. The latter type of workout
tant component in training for most sports as well as
presumably acts by optimising neural adapta-
for injury prevention and rehabilitation.
[1-3]
Quanti-
tions,
[11]
although marked hypertrophy can also oc-
fication of the dose-response relationships between
cur if the volume is sufficient.
[12,15,18]
the training variables (e.g. intensity, frequency and
Scanning methods such as MRI and CT are re-
volume) and the outcome (e.g. strength, power and
garded as the gold standard for assessing whole
hypertrophy) is fundamental for the proper prescrip-
muscle size.
[19,20]
To our knowledge, no systematic
tion of resistance training.
[4]
Several meta-analy-
review has been published that has analysed the
ses
[4-8]
and numerous reviews
[1,3,9-11]
have dealt with
impact of several important training variables
various aspects of optimising strength; however,
such as frequency, intensity and volume on changes
with the exception of a paper by Fry,
[12]
few system-
in muscle area or volume as measured by scanning
atic reviews have focused on the issue of how to
methods. Such a review could provide evidence-
train specifically for muscle hypertrophy. The re-
based guidelines for the prescription of strength
view of Fry
[12]
discussed the role of training intensi-
training for increasing muscle mass. Establishing
ty on hypertrophy as measured by increases in mus-
efficient models of strength training for hypertrophy
cle fibre area (MFA).
in humans could also be of value for the study of the
Implicit in many articles in the literature are the
physiological mechanisms of the hypertrophy pro-
following assumptions: (i) training for strength and
cess. Therefore, the purpose of the present study was
training for hypertrophy is essentially one and the
to identify dose-response relationships for the devel-
same thing; and (ii) the programme that yields the
opment of muscle hypertrophy by calculating the
largest increases in strength also results in the larg-
rates and magnitudes of increases in muscle cross-
est increases in muscle mass. These assumptions are
sectional area (CSA) or muscle volume induced by
not necessarily true in all situations. For example,
varying levels of frequency, intensity and volume,
studies by Choi et al.
[13]
and Masuda et al.
[14]
showed
as well as by different modes of strength training.
smaller increases in one repetition maximum (1RM)
and isometric strength, but greater increases in
1. Methods
quadriceps muscle area (as measured by magnetic
resonance imaging [MRI]) and MFA after a typical
1.1 Literature Search
moderate-load bodybuilding regimen when com-
pared with a high-intensity powerlifting pro-
Computer searches in the MEDLINE/PubMed,
gramme. Schmidtbleicher and Buehrle
[15]
showed
SportDiscus
and CINAHL
databases were per-
greater increases for triceps brachii muscle area (as
formed for articles from 1970, when the first train-
measured by CT scanning) for a group that trained
ing study using scanning techniques to evaluate
with 3 sets of 12 repetitions at 70% of 1RM when
changes in anatomical muscle CSA was pub-
compared with a group that trained with 7 sets of
lished.
[21]
In addition, hand searches of relevant
1–3 repetitions at 90–100% of 1RM, while the
journals and books as well as the reference lists of
strength increases for the groups were similar. Thus,
articles already obtained were performed. The data
it is apparent from these and other studies that the
reviewed in this article was accumulated as a result
training prescription for hypertrophy may differ
of literature searches conducted for this and other
somewhat from the prescription for maximum
projects over a period of several years. The last
strength. This observation has been taken into ac-
search was performed on 3 December 2006. As the
count in various models of periodisation,
[16,17]
where
search progressed, it quickly became apparent that
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228 Wernbom et al.
the quadriceps was by far the most studied muscle 1.2 Classification of Muscle Actions, Training
Methods and Modalities
group in humans undergoing strength training and
that the elbow flexors (biceps brachii and brachialis)
For the purposes of this review, the terminology
were the second most studied muscle group. Cur-
of Knuttgen and Komi
[22]
was adopted for the classi-
rently, these are probably the only muscle groups
fication of muscle actions. Accordingly, exercise
that allow for meaningful evaluation of dose-re-
can be classified as either static (involving isometric
sponse trends. Therefore, the present review is fo-
muscle actions) or dynamic (involving concentric
cused on the human quadriceps and elbow flexors.
and/or eccentric muscle actions). During an isomet-
Criteria for inclusion were as follows:
ric muscle action, the muscle develops force but no
1. Studies must have examined the effects of
external movement occurs and the length of the
strength training on anatomical muscle area or mus-
muscle-tendon complex does not change. During a
cle volume by a scanning method (i.e. MRI, CT or
concentric action, the muscle produces force while
ultrasound [UL]).
shortening. An eccentric muscle action refers to a
situation where the muscle produces force while
2. Studies must have been conducted on healthy and
lengthening.
uninjured participants between 18 and 59 years of
In resistance exercise, training methods or mo-
age.
dalities are often classified according to the type of
3. Sufficient data to calculate changes in muscle area
resistance used. In his 1981 review, arguably the
or volume must have been reported.
first systematic look at strength training, Atha
[9]
4. Sufficient information regarding the training vari-
divided the training modes into three main catego-
ables (in particular: frequency, intensity and vol-
ries: (i) isotonic; (ii) isokinetic; and (iii) isometric.
ume) and the type and mode of exercise employed Isometric training obviously involves isometric ac-
tions. Isotonic training refers to dynamic exercise in
must have been reported to allow for replication of
which the muscle(s) exerts a constant tension.
[22]
In
the study.
various textbooks of physiology, an isotonic muscle
Exclusion criteria were as follows:
action is often illustrated by an isolated muscle that
1. The subjects received supplements (e.g. creatine
is shortening or lengthening against a constant load,
monohydrate, amino acids, proteins) or anabolic
thus developing a constant force. This is not true in
hormones and/or growth factors that could poten-
the intact muscle of a person performing an exercise
tially have influenced the neuromuscular adapta-
because of biomechanical factors such as changes in
tions to strength training. Such study groups (but not
the lengths of the lever arms of the muscle and of the
necessarily other groups from the same study) were
resistance, and also the accelerations and decelera-
excluded from the current review.
tions that occur during dynamic exercise. Thus, even
if the external resistance remains constant, the mus-
2. The subjects were in negative energy balance (i.e.
cle will not develop a constant level of force.
[22,23]
on a weight-loss diet).
For this reason, the term ‘isotonic’ is often replaced
3. The data from the study have been published
by the term ‘dynamic constant external resistance’
before. However, sometimes it was necessary to
(DCER).
[23]
In DCER exercise, the absolute load is
collect data from several different papers from the
constant throughout the movement, as when lifting a
same study.
dumbell. Further examples of DCER would be sim-
4. Only part of the muscle group (e.g. vastus lateral-
ple cable pulley systems with no lever arms and
is) was scanned. Alternatively, only data for the total
machines with circle shaped cams. The term ‘varia-
muscle CSA of the limb (e.g. total thigh muscle
ble resistance’ is used when the resistance through-
area) was reported without specifying CSAs for the
out the range of motion is varied, for example by an
individual muscles (e.g. quadriceps). irregularly shaped camwheel or a lever arm.
[23]
The
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Strength Training and Muscle Cross-Sectional Area 229
idea with variable resistance is to closely match the type of training, but Murphy and Wilson
[29]
have
used the exact same term to describe DCER training.
resistance with the strength of the subject through-
With isoinertial flywheel ergometers, as with
out the range of motion.
[24]
However, because many
isokinetic training, the resistance is effort dependent
dynamic training studies did not specify if the resis-
for each type of action. Therefore, this mode of
tance was constant or variable, no distinction be-
exercise will be included in the ‘accommodating
tween these subcategories was made in the present
resistance’ category.
review. The overall category for both these subcat-
egories is termed dynamic external resistance
1.3 Quantification of Exercise Frequency,
(DER).
Intensity and Volume
In isokinetic training, muscle actions are per-
formed at a constant angular velocity, which is
Regarding exercise intensity in dynamic external
controlled by the machine. Unlike dynamic external
resistance training, we chose to express intensity as
resistance training, there is no set resistance to over-
a function of 1RM in the exercise(s) performed for
come; however, since the velocity is controlled, any
the muscle group in question (e.g. 80% of 1RM in
force applied against the equipment results in an
the squat). In many of the studies, the authors pro-
equal and opposite reaction force.
[23]
Since the sub-
vided exact percentages or at least estimates of the
ject can freely vary the level of effort in the entire
percentage. In cases where the intensity was ex-
movement to accommodate for pain or weakness in
pressed only as a function of how many repetitions
certain regions of the range of motion, the isokinetic
the subjects were able to perform (e.g. 8RM), we
mode is very useful in rehabilitation.
[24]
Isokinetics
estimated the relative intensity based on data on the
are sometimes sorted into a category called ‘accom-
relationship between the number of repetitions per-
modating resistance’.
[25]
Also included in this cate-
formed and the 1RM for the same or similar exer-
gory are devices in which the resistance is provided
cises.
[2,30-33]
For the squat, we used the RM tables of
by hydraulic cylinders, which function by limiting
Wathan,
[32]
which have been shown to be accurate
the flow through an adjustable aperture. Although
for the squat in previously untrained subjects.
[33]
For
not providing a strictly isokinetic movement, the
the leg press, knee extension and arm curl exercises,
resistance setting on these machines can be adjusted
we used data from Hoeger et al.
[30]
The intensity for
to limit the velocity within relatively narrow
isometric training was quantified as a function of the
ranges.
[25]
These devices are sometimes also re-
maximum force achieved during a maximal volunta-
ferred to as semi-isokinetic.
[26]
For the purposes of
ry isometric action (MVIA).
this review, the term ‘accommodating resistance’
While the quantification of exercise intensity in
was chosen for the main category. Another form of
conventional resistance training and isometric train-
strength training uses the inertia of a flywheel for
ing is relatively straightforward, how to express the
resistance. In this type of ergometer, the force exert-
intensity or load for isokinetic and other accommo-
ed by the subject is transferred to a strap being
dating training modes is less obvious. The force-
wound around the axle of a fixed flywheel.
[27]
A
velocity relationship of skeletal muscle dictates that
concentric muscle action unwinds the strap and
as the velocity of the concentric muscle action in-
overcomes the inertia of the flywheel, setting it
creases, the maximum possible force decreases.
[34,35]
spinning on low friction bearings. The rotating fly-
Depending on the training status, the maximum
wheel soon causes the strap to start winding up
torque developed by the quadriceps during eccentric
again; therefore, the machine returns the stored en-
muscle actions is slightly higher (trained subjects) or
ergy of the spinning flywheel via the strap and the
not significantly higher (sedentary subjects) than the
subject tries to resist the returning movement by
maximum isometric torque.
[35]
In cases where the
performing an eccentric muscle action. Caruso et
peak torque during eccentric muscle actions exceeds
al.
[28]
have used the term ‘isoinertial’ to describe this
that of isometric muscle actions, the peak torque
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230 Wernbom et al.
increases only marginally with increasing velocity sessions per muscle group per week, as opposed to
training days per week. For example, a training
and appears to reach a plateau at relatively low
group may have trained the quadriceps twice a day,
velocities.
[35]
The amount of force developed by the
three days a week. The frequency then is reported as
muscle is generally regarded as an important stimuli
six times per week. We are aware of the possibility
for muscle hypertrophy.
[36]
Since maximum effort
that the physiological responses may differ between
(and therefore, recruitment of the greatest number of
training once a day six times per week and twice a
motor units possible) was used in most accommo-
day three times per week.
dating training studies, an estimate of the torque
developed in relation to the isometric maximum
1.4 Classification of Training Status
could provide some insight into the level of force
necessary to produce hypertrophy as a consequence
In the majority of the studies, the subjects were
of accommodating resistance training. Therefore, in
reported as either untrained/sedentary or as physi-
addition to listing the training velocity, level of
cally active. Physically active subjects generally
effort and type(s) of muscle action(s), we estimated
performed some form of endurance training, but not
the relative level of torque normalised to the maxi-
any systematic strength training. Since many studies
mum isometric torque based on the peak torque data
reported varying levels of activity among the partici-
for the quadriceps in untrained subjects from
pants and because endurance training induces little
Amiridis et al.
[35]
For the elbow flexors, data from
if any muscle hypertrophy,
[39]
the categories ‘un-
Hortobagyi and Katch
[37]
and Paddon-Jones et al.
[38]
trained’ and ‘physically active’ were combined for
were used.
analyses. Deschenes and Kraemer
[40]
made the fol-
lowing classification of training status with refer-
Training volume is a measure of the total amount
ence to resistance training: untrained, moderately
of work (joules) performed in a given time peri-
trained, trained, advanced and elite. They suggested
od.
[23]
In this review, training volume refers to a
that the window of adaptation for strength becomes
single session. In a less strict sense, volume can be
progressively smaller as the subject progresses.
estimated by the sum of repetitions
[23]
or even by the
However, because of the lack of studies involving
number of sets performed.
[4]
While simply stating
athletes of different training status, data from studies
the number of sets may seem a crude measure of
with trained, advanced and elite athletes are dis-
volume, several meta-analyses
[4-6,8]
have shown sig-
cussed together in the present review. In cases where
nificant differences in strength gains between train-
the strength training status of the subjects was un-
ing with single and multiple sets in favour of multi-
certain, information was sought regarding the CSA
ple sets, particularly for trained subjects. Theoreti-
of the exercised muscles and comparisons were
cally, a given exercise volume can be distributed in
made with data from previously untrained individu-
many different ways and as a consequence result in
als
[41-45]
and resistance-trained subjects and strength
different adaptations. Therefore, several estimates
athletes.
[41,45-47]
of volume (number of sets, total number of repeti-
tions, total duration of work and total work) were
1.5 Calculation of Changes and Rate of
used in this review. However, instead of expressing
Changes in Muscle Cross-Sectional
the total amount of work performed in joules, work
Area (CSA)
was calculated in arbitrary units (sets × repetitions ×
intensity).
[25]
If several exercises were performed for
In most of the studies reviewed here, the authors
the muscle group (e.g. leg presses and knee exten-
reported the changes in CSA or at least the pre- and
sions for the quadriceps), the volumes for each of
post-training values. Sometimes, figures were used
these were summed to yield the total volume for the
instead of numerical data; in such cases the graphs
muscle group. Regarding the training frequency, we
were measured if possible. The relative changes
have chosen to report frequency as the number of
were calculated by simply dividing the post- with
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Strength Training and Muscle Cross-Sectional Area 231
the pre-training values. To allow for comparisons contributing mechanism for whole muscle hypertro-
phy.
between studies of different length, percent changes
This is of course not to say that changes in fibre
per day were calculated by dividing the change in
area are irrelevant as an index of muscle mass.
area with the length of the training period in days.
Ideally, a training study would include measure-
Although some studies
[43,48]
have shown preferential
ments at both the cellular level and at the whole
hypertrophy of individual muscles in a muscle group
muscle level. Also, it should be noted that the rela-
and of different levels in the same muscle, no con-
tive changes in mean fibre area are usually of a
sistent pattern has yet emerged. Furthermore, data
larger magnitude than the changes in anatomical
from other studies
[44,49]
suggest that changes in mus-
muscle area.
[44]
However, we feel that the focus on
cle CSA at the middle level and muscle volume after
changes in whole muscle CSA and volume, as mea-
a training period are of a similar magnitude. In
sured by scanning techniques, is justified since these
addition, studies by Aagaard and co-workers
[50]
and
are arguably the most sensitive and representative
Tracy et al.
[51]
have confirmed that quadriceps mus-
measures of whole muscle mass, even though they
cle volume can be accurately predicted from a single
may underestimate the changes at the cellular level.
scan at the middle level. Therefore, no distinction
Regarding training issues where the evidence at the
was made in this review between muscle volume
whole muscle level is limited, we will discuss rele-
and CSA as indexes of muscle size. A further dis-
vant studies, if any, which have measured MFA
cussion on the subject is provided by Tracy and
changes.
colleagues.
[52]
2. Results Part 1: Quadriceps Studies
There are several reasons for focusing mainly on
changes in whole muscle CSA and not MFA. As
argued by Narici and colleagues
[43]
and D’Antona et
2.1 Quadriceps Studies: Dynamic
al.,
[47]
care should be taken when drawing conclu-
External Resistance
sions concerning the whole muscle mass from
After application of the inclusion and exclusion
changes occurring at a single biopsy site. In the
criteria, the literature search resulted in 44 original
study of Narici et al.,
[43]
the changes in mean fibre
articles
[13,43-46,54-92]
investigating quadriceps muscle
area (2% increase in MFA) were not representative
CSA or volume before and after DER training.
of either the vastus lateralis at the same level as the
Because there were often more than one training
biopsy site (7.5% increase in muscle CSA by MRI),
group or more than one limb that received training,
or of the quadriceps as a whole (16% increase in
these 44 articles yielded 65 datapoints for CSA. Five
muscle CSA). Apart from the obvious risk of not
of the articles (seven datapoints) involved trained to
detecting hypertrophy because of sampling muscle
elite strength athletes. These were too few to allow
tissue from just a single site in a very large and
for any meaningful analysis and will be discussed
architecturally complex muscle group such as the
briefly in sections 4.1 and 4.6. Five studies dealt
quadriceps, the lower limit for the increase in fibre
with pure concentric and/or eccentric training, with
size that can be detected is 10%. Furthermore, the
four datapoints for concentric training and three for
coefficient of variation between repeated biopsies is
eccentric training. Four datapoints from four differ-
quite large, 15–20% (see Narici et al.
[43]
for discus-
ent studies involved training where the subjects fin-
sion). Thus, hypertrophic changes that are detecta-
ished each set with several repetitions in reserve.
ble at the whole muscle level may go unnoticed if
Since stopping well short of muscular failure has
only fibre areas are measured. Finally, as discussed
been shown to yield modest hypertrophy in compar-
by McCall and colleagues,
[53]
one should be cau-
ison with performing each set to muscular failure,
[85]
tious in ruling out hyperplasia (an increase in the
even when the total volume is similar, these study
number of muscle fibres in a muscle) as a possible
groups were excluded. As a result, except where
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232 Wernbom et al.
otherwise indicated, the analysis for DER deals with sions per week, the increase was 0.11% per day
training using combined concentric-eccentric mus- (range: 0.04-0.26%).
cle actions (47 datapoints), with previously un-
2.1.4 Intensity
trained subjects.
The mean peak intensity (the highest value
reached during a session, averaged over the entire
2.1.1 Length of Training Period, Average Increase
in CSA and CSA Per Day
period) was 73% of 1RM. The average intensity (the
mean of all training sets) was 66% of 1RM. Inspec-
The average length of the training period was 79
tion of figure 2 reveals a tendency for greater rates
days. The shortest study was 14 days and the longest
of increase for intensities >60% of 1RM when com-
lasted 6 months. The average increase in quadriceps
pared with intensities below this level; however, it
CSA was 8.5% (range: 1.1–17.3%). The average
should be noted that only six datapoints involved
increase per day in CSA for training with combined
training with mean peak intensities <60% of 1RM.
concentric-eccentric muscle actions (47 datapoints)
The study of Abe et al.
[84]
is not shown because of
was 0.12% per day (range: 0.04–0.55%). If the study
the unusually high training frequency (12 times per
of Abe et al.
[84]
is excluded as an ‘outlier’ because of
week) and very high rate of increase. The peak
the unusually high training frequency and rate of
intensity in this study was 20% of 1RM.
gain, the average increase was 0.11% per day
(range: 0.04–0.26%). For pure concentric training,
2.1.5 Volume
the increase was 0.06% per day and for pure eccen-
The mean number of sets was 6.1 and the mean
tric training 0.03% per day.
number of total repetitions was 60. The results are
shown in figure 3. The study of Abe et al.
[84]
was not
2.1.2 Rate of Gain in CSA: Men versus Women
included in the following analysis of volume. In-
In six studies, groups of men and groups of
spection of the datapoints revealed four identifiable
women followed exactly the same training program-
‘clusters’ in the range of total repetitions. Fourteen
mes. The average increases in CSA per day in these
datapoints were found in the range of 21–39 repeti-
studies were 0.13% for men and 0.14% for women.
tions, 14 datapoints in the range of 40–60 repeti-
Because these differences were considered as negli-
tions, 11 datapoints in the 66–90 repetition range
gible and because several studies contained groups
and finally 6 datapoints in the range 100 repetitions
consisting of both men and women, data from all
per session. The average rate of increase of CSA for
studies were pooled in the analysis for DER training
each cluster was as follows: 21–39 repetitions =
(section 2.1).
0.12% per day; 40–60 repetitions = 0.13% per day;
2.1.3 Frequency
66–90 repetitions = 0.08% per day; and 100 repeti-
The mean training frequency was 2.8 times a tions = 0.12% per day. No studies were found that
week. The most common frequency was three times
a week (22 of 47 datapoints), followed by two times
a week (17 datapoints). Frequencies between and
above these (2.3–4 times per week) were noted in a
few cases. No studies were found that involved
training at frequencies of more than two times per
week. A plot of frequency versus percentage in-
crease in quadriceps CSA per day is shown in figure
1. The highest rate of increase (0.55% per day) was
reported for the training study
[84]
with the highest
frequency (12 times per week). For the frequency of
two sessions per week, the average increase was
0.11% per day (range: 0.03–0.21%); for three ses-
0
0.1
0.2
0.3
0.4
0.5
0.6
02468101214
Number of sessions per week
Increase in CSA per day (%)
1 3 5 7 9 11 13
Fig. 1. Frequency of training vs percentage increase in cross-sec-
tional area (CSA) per day of the quadriceps during dynamic exter-
nal resistance trainin
g
(
number of stud
y
g
roups = 47
)
.
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Strength Training and Muscle Cross-Sectional Area 233
2.2.1 Length of Training Period, Average Increase
in CSA and CSA Per Day
The average length of the training period was 52
days. The shortest study was 13 days and the longest
lasted 84 days. The mean total increase in CSA was
5.8% (range: 2.5–18.4%) for all types muscle action
combined. For pure concentric training, the mean
total CSA increase was 6.1% (range: 2.5–18.4%),
for pure eccentric training the mean increase was
4.2% (range: 2.5–6.2%) and for combined concen-
tric-eccentric training, the corresponding figures
were 6.0% (range: 4.1–7.4%). The mean CSA in-
Increase in CSA per day (%)
0
0.05
0.1
0.15
0.2
0.25
0.3
Intensity (% of 1RM)
010
20
30 40 50 60 70 80 90 100
Fig. 2. Peak intensity of training vs percentage increase in cross-
sectional area (CSA) per day of the quadriceps during dynamic
external resistance training (number of study groups = 46). RM =
repetition maximum.
crease per day for pure concentric training was
0.13% (range: 0.05–0.44%), for pure eccentric train-
involved <21 repetitions per session on average. For
ing 0.06% (range: 0.04–0.09%) and for combined
concentric-eccentric training 0.16% (range:
the number of sets, the following groupings were
0.06–0.21%). The average CSA increase for all the
made: 3 sets (average CSA increase = 0.09% per
accommodating resistance modes combined was
day); 4 sets (0.13% per day); 5–6 sets (0.13% per
0.13% per day.
day); 7–9 sets (0.09% per day); and 10 sets (0.14%
per day). No studies were found which involved <3
2.2.2 Frequency
sets. When training volume was expressed in arbi-
The mean frequency for concentric training was
trary units [sets × repetitions × intensity], no appar-
3.4 times a week. Three sessions (nine datapoints)
ent relation was found between the volume and
per week yielded an average increase in CSA of
increases in CSA per day (data not shown).
0.13% per day and 3.5–4 sessions per week (four
datapoints) yielded an average increase in CSA of
0.12% per day. Five sessions (one datapoint) per
2.2 Quadriceps Studies:
week yielded an average increase in CSA of 0.22%
Accommodating Resistance
per day. The largest rate of CSA increase (0.44% per
day) was noted in a study
[104]
using three sessions
The literature search resulted in 17 original arti-
per week. No concentric training studies were found
cles
[27,42,48,87,93-105]
investigating quadriceps muscle
with training frequencies below three sessions per
CSA or volume before and after an accommodating
week or above five sessions per week. The frequen-
resistance-training programme. These 17 articles
yielded 21 datapoints for CSA. Of these, 14
datapoints involved pure concentric training, three
involved pure eccentric training and four involved
training with combined concentric-eccentric muscle
actions. Some of the studies
[93,95-98]
included sub-
jects with strength training experience. Based on
anthropometric and quadriceps muscle CSA data,
they were considered as ‘moderately trained’ and
are included in the analysis in sections 2.2.1–2.2.7,
together with previously untrained and physically
active individuals.
0
0.05
0.1
0.15
0.2
0.25
0.3
0 20 40 60 80 100 120 140 160
Total number of repetitions per session
Increase in CSA per day (%)
Fig. 3. Total number of repetitions vs percentage increase in cross-
sectional area (CSA) per day of the quadriceps during dynamic
external resistance trainin
g
(
number of stud
y
g
roups = 45
)
.
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234 Wernbom et al.
When the percentage values for eccentric torque
were applied and all accommodating modes and
types of muscle actions were combined, no relation
was found between the maximum torque developed
during training and the rate of increase in quadriceps
CSA (see figure 5).
2.2.5 Volume
For pure concentric training, the largest increases
occurred when the total number was between 50 and
60 muscle actions (six datapoints, 0.19% increase in
Increase in CSA per day (%)
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0123456
Number of sessions per week
Fig. 4. Frequency of training vs percentage increase in cross-sec-
tional area (CSA) per day of the quadriceps during accommodating
concentric and/or eccentric trainin
g
(
number of stud
y
g
roups = 21
)
.
CSA per day [0.13% increase in CSA per day with-
out the studies of Akima et al.
[103]
and Rafeei
[104]
]).
cy for pure eccentric training was three times per
Two datapoints were found in the interval of 30–40
week in all studies (three datapoints). For the com-
muscle actions (0.06% increase in CSA per day) and
bined concentric-eccentric training regimens, the
six datapoints between 120 and 480 muscle actions
frequencies were two (one datapoint), 2.3 (two
(0.10% increase in CSA per day). If studies with
datapoints) and three (one datapoint) times per
pure eccentric and combined concentric-eccentric
week. The frequency plot for all categories com-
muscle actions are included in the analysis, the
bined is shown in figure 4. No relationship between
increases still tend to reach their maximum in the
the frequency and the rate of CSA increase is appar-
range between 50 and 60 muscle actions per session
ent from figure 4.
(ten datapoints, 0.18% increase in CSA per day).
See figure 6.
2.2.3 Velocity
Regarding the number of sets for pure concentric
For pure concentric training, the most common
training, one datapoint was found for 3 sets, one for
velocities were 60°/s (seven datapoints, 0.13% in-
4 sets, six for 5–6 sets, none for 7–9 sets and six for
crease in CSA per day) and 120°/s (four datapoints,
10 sets. The highest increase occurred at 5–6 sets
0.16% increase in CSA per day). Two studies used
(0.19% increase in CSA per day [0.13% increase in
180°/s (0.14% increase in CSA per day) and one
CSA per day minus Akima et al.
[103]
and
study used 90°/s (0.05% increase in CSA per day).
Rafeei
[104]
]). The increase in CSA for 10 sets was
The velocities for eccentric training and combined
0.10% per day and the increase for 3–4 sets was
concentric-eccentric training were in the range be-
0.06%. If studies with pure eccentric and combined
tween 45 and 90°/s.
2.2.4 Torque
Data from Amiridis et al.
[35]
on untrained subjects
suggests that the isokinetic concentric peak torque
of the quadriceps expressed as a percentage of maxi-
mum isometric torque is 59%, 69%, 77% and 88%
at the velocities of 180°/s, 120°/s, 90°/s and 60°/s,
respectively. When these percentage values were
applied to the concentric training studies, no relation
was found between the level of torque developed
and the rate of increase in CSA. The eccentric peak
torque of the quadriceps in relation to the maximum
isometric torque is 104%, 106% and 104% at the
velocities of 30°/s, 60°/s and 90°/s, respectively.
Increase in CSA per day (%)
0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80 100 120
Torque (% of MVIA)
Fig. 5. Torque vs percentage increase in cross-sectional area
(CSA) per day of the quadriceps during accommodating concentric
and/or eccentric training (number of study groups = 21). MVIA =
maximal voluntar
y
isometric action.
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Strength Training and Muscle Cross-Sectional Area 235
tween 25 and 50 units (0.14% increase in CSA per
day), six between 50 and 100 units (0.14% increase
in CSA per day) and five in the interval between 100
and 265 units (0.10% increase in CSA per day).
2.3 Quadriceps Studies: Isometric Resistance
The literature search resulted in six original arti-
cles
[55,106-110]
investigating quadriceps muscle CSA
or volume before and after an isometric resistance
training programme, yielding nine datapoints for
CSA.
2.3.1 Length of Training Period, Average Increase
Increase in CSA per day (%)
0
0.1
0.2
0.3
0.4
0.5
0 50 100 150 200 250 300 350 400 450 500
Number of muscle actions per session
Fig. 6. Number of muscle actions vs percentage increase in cross-
sectional area (CSA) per day of the quadriceps during accommo-
dating concentric and/or eccentric training (number of study groups
= 21
)
.
in CSA and CSA Per Day
The average length of the training period was 84
concentric-eccentric muscle actions are included in
days. The shortest study was 56 days and the longest
the analysis, the results are as follows: 3 sets (two
lasted 98 days. The mean increase in total CSA after
datapoints) = 0.08% increase in CSA per day; 4 sets
the training period was 8.9% (range: 4.8–14.6%)
(six datapoints) = 0.12% increase in CSA; 5–6 sets
and the average rate of CSA increase was 0.11% per
(seven datapoints) = 0.17% increase in CSA (0.11%
day (0.06–0.26%).
without the studies of Akima et al.
[103]
and
Rafeei
[104]
); and 10 sets (six datapoints) = 0.10%
2.3.2 Frequency
increase in CSA per day.
Three sessions per week (four datapoints) result-
ed in an increase in CSA of 0.12% per day and four
2.2.6 Total Duration Per Session
sessions per week (five datapoints) resulted in an
For pure concentric training, eight datapoints
increase in CSA of 0.11% per day. The largest rate
were distributed between 37.5 and 75 seconds of
of gain (0.26% increase in CSA per day) was report-
total duration of muscle work. The average increase
ed in a study
[106]
using three sessions per week.
in CSA for these datapoints was 0.16% per day. The
other six datapoints were distributed between 170
2.3.3 Intensity
and 300 seconds. The average increase in CSA for
The most common intensity was 70% of MVIA
these datapoints was 0.09% per day. For the pure
(seven datapoints), the intensity in the other two
eccentric and combined concentric-eccentric train-
cases was 80% and 100%, respectively. The largest
ing groups taken together, the seven datapoints (av-
rate of CSA increase (0.26% per day) was found in
erage of 0.12% increase in CSA per day) were
the study
[106]
that used the highest training intensity
distributed between 40 and 84 seconds.
(100% of MVIA).
2.2.7 Time-Torque Product Per Session 2.3.4 Volume
The time-torque product per session was calcu- The total number of repetitions ranged between 4
lated by multiplying the total duration with the esti- and 150. The time each repetition was held ranged
mated peak torque (with maximum isometric torque between 1 and 30 seconds, while the total duration
assigned a value of 1) and is reported here in arbitra- of muscle work per session was between 80 and 150
ry units. No relation was found between the time- seconds. No relation was found between the number
torque product and the rate of gain in CSA, regard- of repetitions and the increase per day in CSA.
less of whether eccentric and combined concentric- Similarly, when volume was expressed as the total
eccentric training was included in the analysis or not duration per session and as the product of intensity
(data not shown). For all types of muscle actions and total duration, no apparent relation between
combined, ten datapoints were in the interval be- volume and rate of increase in CSA was observed,
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236 Wernbom et al.
although the highest rate of increase in CSA (0.26% increase in quadriceps CSA (34%) was noted in one
per day) was observed for the training study
[106]
with of the longer studies,
[112]
after 20 weeks of training
the largest product of intensity and duration. (see figure 7). There was also an apparent tendency
for the rate of increase in CSA to decrease with
2.4 Quadriceps Studies: Combined Strength
increasing lengths of the training period (figure 8). If
and Endurance Training
one regards the studies of Abe et al.
[84]
and
Rafeei
[104]
as outliers because of their unusually high
The literature search resulted in seven original
rates of increase, the slope becomes less steep.
articles
[77,78,86,96,111-113]
investigating quadriceps
muscle CSA or volume before and after a combined
2.6 Quadriceps Studies: Strength Training as
training programme, yielding ten datapoints. Some
a Countermeasure During Unloading
of the studies included groups that performed only
strength training, these have been included in sec-
The literature search resulted in eight original
tions 2.1 and 2.2. Because of the limited data and
articles
[114-121]
investigating quadriceps muscle CSA
different modes of endurance training (rowing, run-
or volume before and after a resistance training
ning and cycling), as well as the different modes of
programme as a countermeasure during otherwise
strength training, no analysis was performed regard-
unloaded conditions (bed rest or limb suspension).
ing frequency, intensity and volume.
These eight papers yielded nine datapoints for CSA
for the training groups and nine datapoints for the
2.4.1 Rate of Gain in CSA: Combined Training
control groups, which performed no training. One
versus Pure Strength Training
study (one datapoint) used isometric training as a
In four of seven studies,
[77,78,96,111]
comparisons
countermeasure, one study (one datapoint) used vi-
were made between pure strength training and com-
bration combined with isometric training, four stud-
bined training regarding increases in quadriceps
ies (five datapoints) used dynamic external resis-
CSA. If these are summarised, the resulting average
tance with coupled concentric-eccentric muscle ac-
increases are as follows: pure strength training =
tions and two studies (two datapoints) used
0.09% increase in CSA per day; and combined
accommodating resistance with coupled concentric-
training = 0.10% increase in CSA per day. If the
eccentric muscle actions.
combined training groups of the other three stud-
ies
[86,112,113]
are included, the average rate of CSA
2.6.1 Unloading versus Unloading and
Exercise Countermeasure
increase for combined training becomes 0.12% per
day.
The average length of the training and unloading
period was 49 days (range: 20–119 days). The mean
2.4.2 Length of Training Period and Increase
decrease in quadriceps CSA for unloading was
in CSA
The shortest study was 70 days and the longest
lasted 168 days. The mean total increase in CSA
after the training period was 15.1%. The largest
increase in CSA was 34% (0.24% per day) and the
smallest was 3.9% (0.05% per day).
2.5 Quadriceps Studies: All Voluntary
Training Modes
2.5.1 Length of Training Period and Increase
in CSA
Longer training periods generally tended to result
in larger increases in CSA. Accordingly, the greatest
Increase in total CSA (%)
0
5
10
15
20
25
30
35
40
0 20 40 60 80 100 120 140 160 180 200
Length of traning period (days)
Fig. 7. Traning period vs total percentage increase in cross-section-
al area (CSA) of the quadriceps during all types of voluntary
stren
g
th trainin
g
(
number of stud
y
g
roups = 91
)
.
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Strength Training and Muscle Cross-Sectional Area 237
timulation to evoke muscle actions. In the first of
these,
[99]
previously untrained subjects performed
3–5 sets of 10 unilateral combined concentric and
eccentric actions in an isokinetic dynamometer at a
velocity of 75°/s, for two sessions per week for 9
weeks. The increase in quadriceps CSA was 10.1%
(0.16% per day). In the second study,
[122]
from the
same research group, recreationally resistance-
trained subjects performed an identical protocol to
that in the first study, for two sessions per week for 8
weeks. These subjects continued their normal resis-
Increase in CSA per day (%)
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 40 60 80 100 120 140 160 180 200
Length of training period (days)
Fig. 8. Training period vs percentage change in cross-sectional
area (CSA) per day of the quadriceps during all types of voluntary
stren
g
th trainin
g
(
number of stud
y
g
roups = 91
)
.
tance-training regimens during the study, including
exercises for the quadriceps of both sides. The in-
11.1% and the mean rate of decrease was
0.30%
crease in CSA was 9.8% (0.18% per day). The
per day. The degree of loss appeared to be related to
control limb that performed only regular resistance
the length of the unloading period, as the largest
exercise showed no increase in quadriceps CSA.
decrements in CSA were found in the studies with
Another group performed exactly the same pro-
the longest unloading period. However, the rate of
gramme but also received creatine supplementation.
loss in CSA seemed to decrease with the length of
This group increased the CSA with 12.1% (0.22%
the unloading period, so that the longer studies
per day) but this was not significantly greater than
showed lower average rates of change. For the un-
the other (placebo) group. The control limb that
loading plus strength training countermeasure, the
performed regular resistance exercise only showed a
CSA increased by an average of 1.3% (0.03% per
slight increase (5%) in quadriceps CSA. In the third
day). If the isometric training and the vibration
study,
[123]
electromyostimulation was used to evoke
training groups are excluded, the increase in CSA
40 isometric muscle actions per session, four ses-
becomes 2.7% (0.09% per day). The largest total
sions a week for 8 weeks. The increase in CSA was
CSA increase was 7.7% (0.22% per day) and the
6% (0.11% per day).
largest rate of gain was 0.30% per day (6.0% in total
CSA). The greatest total CSA decrement was
3.8% 3. Results Part 2: Elbow Flexor Studies
(
0.19% per day) for the isometric countermeasure.
The greatest total CSA decrease for the dynamic
3.1 Elbow Flexor Studies: Dynamic
groups was
1.9% (
0.02% per day). Because of the
External Resistance
limited data and differences in both training modes
and unloading models, no analysis was performed
The literature search resulted in 16 original arti-
regarding frequency, intensity and volume. The
cles
[25,53,124-137]
investigating elbow flexor (biceps
lowest training frequency was every third day (2.3
and brachialis) muscle CSA or volume before and
times per week) and the highest was twice a day (14
after a DER training programme with specific exer-
times per week).
cises for the elbow flexors. These papers yielded 36
datapoints for CSA. Three of the papers (seven
datapoints) included highly-trained subjects, while
2.7 Quadriceps
one paper included recreationally-trained subjects
Studies: Electromyostimulation
(one datapoint), who had previously trained without
The literature search resulted in three original any structured programmes or specific goals. Based
articles
[99,122,123]
investigating quadriceps muscle on strength and CSA data, the latter group was
CSA in healthy uninjured subjects before and after a regarded as ‘moderately trained’ and included in the
resistance training programme using electromyos- analysis of ‘untrained’ and ‘physically active’ sub-
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238 Wernbom et al.
3.1.3 Intensity
jects in sections 3.1.1–3.1.4. Four groups (four
The mean peak intensity (the highest value
datapoints) from three other studies were excluded
reached during a session, averaged over the entire
because they either performed only non-specific
period) was 72%, which was the same as the average
exercises for the biceps and brachialis muscles (e.g.
intensity (the mean of all training sets), since no
latissimus pulldown, dumbell row) or they did not
study reported using different loads during one and
perform their elbow flexor exercises with near maxi-
the same session. The highest mean intensity report-
mal effort or near muscular failure in any set. One
ed was 180% of 1RM, in a study
[126]
that used
group from another study was excluded because the
eccentric overload, in addition to performing the
eccentric phase was performed in a plyometric man-
concentric phase with a lower resistance. This was
ner with the resistance building up momentum
also the only study that used such overload; the
before the subject started to resist it, making it very
others used the same resistance in both types of
difficult to estimate the actual intensity. As a result,
muscle actions. The lowest resistance reported in a
the analysis in sections 3.1.1–3.1.4 for the variables
study was 10%. When the intensity was plotted
of frequency, intensity and volume is based on 24
against the rate of increase, a tendency was found
datapoints for training with previously untrained to
for the rate to increase with increasing intensity. The
moderately trained subjects. All studies involved
highest rates of increase tended to occur around 75%
training with combined concentric-eccentric muscle
of 1RM (see figure 10).
actions, but in one study the eccentric phase was
overloaded with 180% of 1RM.
3.1.4 Volume
3.1.1 Length of Training Period, Average Increase
The results for the number of repetitions versus
in CSA and CSA Per Day
CSA per day are shown in figure 11. The mean
The average length of the training period was 91
number of sets was 5.4 and the mean number of total
days. The shortest study was 30 days and the longest
repetitions was 47. Three clusters of datapoints were
lasted 6 months. The average increase in flexor CSA
identified as follows: (i) 7–38 repetitions (ten
was 15.8% and the average increase per day in CSA
datapoints); (ii) 42–66 repetitions (nine datapoints);
was 0.20%. The highest increase in elbow flexor
(iii) and 74–120 repetitions (five datapoints). The
CSA (33%) was noted in the longest study, after 6
maximum rate of CSA increase was found in the
months of training,
[130]
although an almost equal
interval between 42 and 66 repetitions (0.26% per
increase (32.6%) was observed in another study
day). For 7–38 repetitions, the CSA increase was
after 11 weeks.
[125]
0.15% per day, and for 74–120 repetitions, the rate
was 0.18% per day. For total sets, the rate of CSA
3.1.2 Frequency
increase appeared to peak between 4 and 6 sets (nine
The results are shown in figure 9. The mean
training frequency was 2.9 times a week. The most
common frequency was three times a week (17 of 24
datapoints), followed by two times a week (six
datapoints). The highest frequency was four times
per week. No studies were found that involved train-
ing at frequencies of less than two times per week.
The highest rate of CSA increase (0.59% per day)
was noted for a training study
[128]
with a frequency
of four times per week. For the frequency of three
sessions per week, the average CSA increase was
0.18% per day and for two sessions per week, the
CSA increase was 0.18% per day.
Increase in CSA per day (%)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
01234
Number of sessions per week
Fig. 9. Frequency of training vs percentage increase in cross-sec-
tional area (CSA) per day of the elbow flexors during dynamic
external resistance trainin
g
(
number of stud
y
g
roups = 24
)
.
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Strength Training and Muscle Cross-Sectional Area 239
3.3 Elbow Flexor Studies: Isometric Resistance
The literature search resulted in three original
articles
[21,124,139]
investigating elbow flexor muscle
CSA before and after an isometric resistance train-
ing programme, with a total of three datapoints for
CSA. The mean CSA increase per day was 0.14%.
The largest total increase in CSA (23.0%) was noted
for the longest study,
[21]
which lasted 100 days. The
frequency was six times a week for two studies
[21,124]
(0.23% average CSA increase per day and 0.06%
per day, respectively) and three times per week for
the third study
[139]
(0.13% per day). The intensity in
Increase in CSA per day (%)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60 80 100 120 140 160 180 200
Intensity (% of 1RM)
Fig. 10. Peak intensity of training vs percentage increase in cross-
sectional area (CSA) per day of the elbow flexors during dynamic
external resistance training (number of study groups = 24). RM =
repetition maximum.
the three studies
[21,124,139]
was 100%, 67% and 80%
of MVIA, respectively. The number of total repeti-
datapoints, 0.24% increase in CSA per day). For
tions was 3–24. The total duration of contractile
3–3.5 sets (ten datapoints), the CSA increase was
activity was 30 seconds in two studies
[21,124]
and 96
0.17% per day and for 9 sets (five datapoints) the
seconds in the third study.
[139]
CSA increase was 0.18% per day.
4. Discussion
3.2 Elbow Flexor Studies:
Accommodating Resistance
4.1 Frequency
The literature search resulted in three original
For quadriceps training with dynamic external
articles
[25,48,138]
investigating elbow flexor muscle
resistance, the largest rate of gain in CSA (0.55%
CSA before and after an accommodating resistance
per day) was noted in the study
[84]
with the greatest
training frequency (12 sessions per week). Howev-
training programme, yielding four datapoints for
er, it should be noted that (i) this study lasted for
CSA. Of these, two datapoints involved pure con-
only 2 weeks; (ii) the intensity was 20% of 1RM;
centric training and two involved pure eccentric
and (iii) the training was performed in combination
training. The longest study was 140 days and the
with partial vascular occlusion. Therefore, the re-
shortest was 56 days. The mean CSA increases per
sults from this study should be viewed with caution
day were 0.16% and 0.12% for concentric and ec-
when considering the application of extremely high
centric training, respectively. Both the largest in-
crease in total CSA (16.3%, 0.12% per day) and the
highest rate of CSA increase (0.20% per day, 11%
total increase in CSA) was noted for concentric
training. Because of the lack of data involving pure
concentric training, combined concentric-eccentric
and pure eccentric training, no formal analysis con-
cerning the effects of frequency, intensity and vol-
ume was performed. The frequency was three times
a week for all studies. The number of sets and
repetitions per set was 4.6 and 10, respectively. The
average total duration of contractile activity was
84.8 seconds (range: 13.9–146.2 seconds).
Increase in CSA per day (%)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60 80 100 120 140
Number of repetitions per session
Fig. 11. Total number of repetitions vs percentage increase in
cross-sectional area (CSA) per day of the elbow flexors during
d
y
namic external resistance trainin
g
(
number of stud
y
g
roups = 24
)
.
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240 Wernbom et al.
frequencies in more conventional training. Further- training at 100% of MVIA as a countermeasure,
training once a day was insufficient to prevent all the
more, it is interesting to note that there was no
atrophy. In yet another bedrest study,
[117]
training
difference in the mean rates of increase in CSA
once a day using a leg press, with coupled concen-
between two and three sessions per week for DER
tric-eccentric actions at 90% of 1RM, preserved the
quadriceps training (0.11% vs 0.11% per day, re-
muscle volume but failed to induce significant hy-
spectively). For accommodating resistance training
pertrophy. Further research is obviously needed to
and isometric quadriceps training, it is difficult to
address the effects of different exercise modes and
evaluate any trend because of the limited number of
regimens (e.g. different frequencies and distribu-
studies and the smaller range of frequencies. The
tions of the total training volume), as well as the
highest rate of CSA gain in the isometric category
impact of the unloading model employed.
(0.26% per day) was achieved in a study
[106]
in
which the subjects trained three times per week;
For elbow flexor training with dynamic external
however, this was also the study with the highest
resistance, the greatest rate of increase in CSA
training intensity (100% of MVIA) and the highest
(0.59% per day; 17.7% total increase in CSA) was
product of intensity and total duration. The highest
observed in a study
[128]
with a frequency of four
rate of CSA increase for accommodating resistance
times a week. The second, third, fourth highest
training (0.44% per day) was noted in a study
[104]
increase in CSA rates noted were 0.42%, 0.38% and
that used a frequency of three sessions per week,
0.32% per day, respectively. These three stud-
followed by a study
[103]
that used a frequency of five
ies
[125,126,132]
used a frequency of three times per
times per week (0.22% increase in CSA per day).
week. However, with the exception of these three
High rates of CSA increase (0.17–0.21% per day)
studies, the average values suggest that there is
were also observed in three studies
[27,87,105]
in which
relatively little difference between training the el-
training was performed two to three times per week.
bow flexors two or three times per week, in terms of
the rate of increase in CSA (0.18% per day for both
For the unloading plus resistance exercise coun-
frequencies). However, the highest increase in CSA
termeasure studies, the highest rate of CSA gain
that was noted for two times per week was 0.24%
(0.30% per day) was noted for the study
[115]
with the
per day, compared with 0.42% per day for three
greatest training frequency (14 sessions per week),
times per week. As noted in section 3.2, all accom-
although a high rate of CSA increase (0.22% per
modating resistance training studies involving the
day) was also noted in a study
[118]
with a frequency
elbow flexors used a frequency of three times a
of every third day. However, caution is warranted
week. Regarding frequency for isometric elbow
when comparing the results of these studies because
flexor training, the highest rate of CSA increase
of possible differences in the effects of the different
(0.23% per day) was noted for a study
[21]
with a
models of unloading and/or the exercise regimens.
frequency of six times per week, but this was also
For example, Tesch and co-workers
[118]
employed
the study that had the highest intensity (100% of
limb suspension for unloading and knee extensions
MVIA). Remarkably, this regimen consisted of only
for the exercise countermeasure and showed a
three isometric actions per day, each lasting 10
marked hypertrophic response in the quadriceps of
seconds, thus resulting in a total of 30 seconds of
the unloading plus exercise limb. In a different study
maximal isometric activity each day.
by Alkner and Tesch,
[119]
when using bedrest for
unloading and horizontal squats, but with the exact
While a higher than normal training frequency
same dosage of training as in their other study,
[118]
(four or more times per week) can result in rapid
the exercise resulted in no hypertrophy but still
hypertrophy in the initial stage, it should also be
managed to completely counteract the atrophy that
noted that several of these studies
[84,115,128]
lasted
was evident in the pure bedrest group. Also notable
only between 2 and 4 weeks. It is uncertain if
is that in one bedrest study,
[114]
which used isometric training at these high frequencies would continue to
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Strength Training and Muscle Cross-Sectional Area 241
yield very high rates of increases in CSA or perhaps per week gained significantly more in 1RM strength
and quadriceps CSA (5.99% and 6.75%, respective-
result in diminishing returns or even overtraining
ly) than the group that trained once a week (3.1%
after a longer period. Inspection of the data from the
increase in CSA). There was no difference between
study of Abe et al.
[84]
suggests that the rate of
training two and three times per week. Wirth and
increase in CSA was considerably slower during the
colleagues
[134]
investigated the effects of frequency
second week compared with the first week, drop-
on elbow flexor CSA in subjects that trained once,
ping from a maximum of 1% per day to 0.25%
twice and three times a week for 8 weeks. All groups
per day. Using a frequency of three times a week and
performed several types of arm curls for a total of 5
a protocol of 4 sets of 7 maximal effort concentric-
sets of 8–12 repetitions in each session. The groups
eccentric actions, Seynnes et al.
[105]
showed a rate of
that trained two and three times per week gained
increase of only 0.12% per day during the first 10
significantly more in elbow flexor CSA (6.6% and
days, but 0.25% per day during the last 25 days of a
7.4%, respectively) than the group that trained once
training period that lasted 35 days. Thus, there is a
a week (3.9%).
possibility that training with a frequency of two to
three times per week may start to produce a high rate
The results of Vikne et al.
[79]
and Wirth et al.
[134]
of increase after the first two weeks; because of this
are remarkably similar despite using different mus-
and the paucity of data regarding long-term training
cle groups and training modes. In both reports, two
with high frequencies, it is not possible to say which
and three sessions per week yielded almost twice the
frequency is more optimal in the long run. Neverthe-
increase in muscle CSAwhen compared with one
less, a high frequency (four or more times per week),
session, with no apparent further advantage for three
in combination with relatively non-damaging low-
versus two sessions. This seems logical in view of
to-moderate volume training, may be a good way to
the typical pattern of changes in muscle protein
‘kick-start’ the hypertrophy process. For longer-
synthesis after a resistance training session, with
term training, the studies included in this review
peak synthesis rates observed between 3 and 24
show that frequencies between two and four times a
hours, and with elevated rates sometimes lasting
week can result in CSA gains for periods of up to 6
between 48 and 72 hours after exercise.
[140-143]
How-
months. For previously untrained subjects, no study
ever, it cannot be excluded that larger volumes and/
was found with a training frequency of less than two
or different modes of training would yield different
sessions per week.
results. Furthermore, the total weekly volumes were
not matched between the groups in the studies of
Regarding the impact of training frequency in
Vikne et al.
[79]
and Wirth et al.
[134]
Also, it should be
more advanced trainers, we found nine stud-
noted that most studies on muscle protein synthesis
ies
[45,46,56,61,76,79,133,134,137]
using scanning methods to
in humans after resistance exercise have only stud-
monitor changes in CSA in the quadriceps and/or
ied a time span of up to 48 hours post-exercise.
elbow flexors as a result of training in strength-
trained subjects and strength/power athletes. In two
Anecdotally, many bodybuilders and other
preliminary reports,
[79,134]
different frequencies of
strength athletes only train each muscle group spe-
training were directly compared. Vikne and co-
cifically between one and two times per week,
workers
[79]
investigated the effects of squat training
sometimes even less often. On the other hand,
with an eccentric overload on quadriceps CSA in
weightlifters are known to perform exercises involv-
subjects that trained one, two and three times a week
ing their quadriceps for several sessions per training
for 12 weeks. All groups performed 5 sets of 4
day.
[144]
Tesch
[145]
has remarked that it is not known
repetitions in each session using a squat machine,
if bodybuilding regimens are superior to the training
which was loaded to 50% of 1RM in the concentric
regimens performed by powerlifters and olympic
phase and to 110–135% of 1RM in the eccentric lifters. Training each muscle group once a week has
been shown to result in increases in muscle
phase. The groups that trained two and three times
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242 Wernbom et al.
CSA
[79,134,146]
and lean body mass.
[146,147]
However, mal from the first repetition, there was no relation
the results of Wirth et al.
[134]
and Vikne et al.
[79]
are
between the torque developed and the rate of gain in
supported by data from McLester et al.,
[147]
who
CSA, regardless of whether eccentric muscle actions
using experienced subjects showed superior in-
were included in the analysis or not. This was true
creases in lean body mass for three training sessions
for both the quadriceps (figure 5) and the elbow
per week versus only one per week per muscle
flexors (data not shown). This is contradictory to
group, even when the total weekly volume remained
some of the studies in the literature,
[148-151]
but con-
the same for the two groups.
sistent with other reports.
[55,62,68,69]
It should be not-
H
¨
akkinen and Kallinen
[61]
also investigated the
ed that no accommodating training study was found
effects of different distributions of the same total
in which the level of torque was <60% of MVIA.
volume, in a group of trained female subjects of
In contrast, the study of Farthing and
which some were competitive strength athletes.
Chilibeck
[151]
seems to confirm the importance of
These subjects underwent two three-week periods of
the force developed during training for the hyper-
strength training for the quadriceps, with 3 training
trophic response. In their study, subjects trained
days per week. During one period, the subjects
their elbow flexors in an isokinetic dynamometer,
trained once each training day and during the second
with concentric actions for one arm and eccentric
period the same subjects trained with the same total
actions for the other arm. One group trained with
daily volume but separated into two sessions. Dur-
fast (180°/s) and another group trained with slow
ing the first training period, the subjects did not gain
(30°/s) speed, with all groups training three times
in either strength or quadriceps CSA, but during the
per week and progressing from 2 to 6 sets of 8
second period, the subjects increased significantly in
repetitions over the course of the training period,
both maximum static strength and CSA (4.0% and
which lasted 8 weeks. The hypertrophic response
0.19% per day, respectively). Although some inter-
was evaluated with measurements of muscle thick-
esting trends can be discerned from the data dis-
ness by ultrasound. The greatest increase in thick-
cussed in this section, there is clearly a need for
ness (13% at the middle level) was found in the fast
further research on training frequency in both high-
eccentric group, followed by the slow eccentric
ly-trained and less-trained subjects.
group (7%), the slow concentric group (5%) and
the fast concentric group (2%). The authors inter-
4.2 Intensity
preted their results as a confirmation of the theory
that greater force production leads to greater hyper-
The studies reviewed in this article show that
trophy.
there is a remarkably wide range of intensities that
This interpretation may be premature since the
may produce hypertrophy. Still, there seems to be
protocols differed greatly in terms of torque-time
some relationship between the load (or torque) and
integral and in the volume of work performed. Fur-
the rate of increase in CSA, at least for dynamic
thermore, it is possible that a local overtraining
external resistance training, but this relationship is
response was developing in the slow eccentric
not a straightforward one. In figure 2 and figure 10,
group. Support for this possibility comes from an
it can be seen that the rates of increase are generally
earlier study by Paddon-Jones and colleagues,
[38]
higher for intensities >60% of 1RM than for those
who used very similar eccentric training regimens to
<60% of 1RM, although caution is warranted be-
those in the study of Farthing and Chilibeck.
[151]
cause of the few datapoints <60% of 1RM. Howev-
Their results generally showed increases in elbow
er, it appears that intensities of 70–85% of 1RM
flexor torque for both fast and slow eccentric train-
are sufficient to induce high rates of increase and
ing after 5 weeks of training, but at 10 weeks the
that even heavier loads do not necessarily result in
torque values of the slow group were either halted or
greater CSA gains. In the categories of accommo-
dating resistance, where the effort is usually maxi- even back to the baseline values while the fast group
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Strength Training and Muscle Cross-Sectional Area 243
continued to gain. The authors suggested that the low the reported maximum velocity of unload-
ed knee extensions, which may reach values of
great cumulative stress of the slow protocol had
700°/s.
[154]
caused an overtraining-like response. The results of
Shepstone et al.
[138]
confirmed the findings of Far-
In support of the use of moderately fast concen-
thing and Chilibeck
[151]
regarding the superiority of
tric training, an early study by Thome
´
e et al.
[155]
fast versus slow eccentric training for the hyper-
showed a clear trend (but not significant) for hyper-
trophic response of the elbow flexors. However, this
trophy of type 2 muscle fibres (30–35%) in the
study is open to the same interpretation regarding
vastus lateralis in both the healthy and the injured
the possibility of a local overtraining response in the
limbs in individuals undergoing moderately fast
slow eccentric group, since the difference in torque-
(180°/s) isokinetic concentric training after recon-
time integral between the fast and slow protocol was
struction of the anterior cruciate ligament (ACL).
even greater (>10-fold) than in the preceeding stud-
No such trend was apparent in either limb in the
ies. Moreover, the slight differences in peak torque
group that trained at a low velocity (60°/s). The
between the fast and the slow eccentric velocities in
training was carried out three times per week for 8
the studies mentioned here argues against the level
weeks, with the slow velocity group progressing
of torque as the primary explanation for the differ-
from 3 sets of 10 repetitions to 10 sets of 10 repeti-
ences observed in the hypertrophy of the elbow
tions and the fast group from 3 sets of 15 repetitions
flexors. Recruitment differences between fast and
to 10 sets of 15 repetitions during the time course of
slow eccentric velocities cannot be excluded as a
the study. A CT scan was also performed of the
contributing factor; however, at present there is not
quadriceps and vastus lateralis at mid-thigh level,
enough evidence to support that this occurs. Never-
but unfortunately too few scans were available due
theless, the considerable difference in hypertrophy
to problems with the scanner, thus making it impos-
between fast eccentric and both fast and slow con-
sible to confirm or reject the trend of the fibre CSA
centric training in the study of Farthing and
data at the whole muscle level. However, a study by
Chilibeck
[151]
lends support to the hypothesis that
Frob
¨
ose and colleagues
[156]
also supports the use of
the force developed by the muscle during training is
moderately fast concentric training for the quadri-
an important factor for hypertrophy.
ceps, at least in the rehabilitation setting. These
authors investigated the effects of isokinetic concen-
At present, there are no accommodating resis-
tric training in patients that had undergone recon-
tance training studies that have investigated the im-
struction of the ACL and they showed hypertrophy
pact of different eccentric velocities and/or different
of the quadriceps in response to moderate (150°/s)
levels of torque development during eccentric mus-
and fast (240°/s) protocols, which was at least equal
cle actions on the CSA of the human quadriceps as
to that of the slow protocol (60°/s). Thus, it appears
measured by scanning methods. There is also a lack
that hypertrophy can be induced in the human quad-
of direct comparisons using accommodating con-
riceps as a result of concentric training at velocities
centric training at different velocities and/or differ-
of up to at least 240°/s and torque levels as low as
ent levels of torque development. The studies re-
50% of MVIA.
viewed in this article suggest that hypertrophy can
be induced with a range of concentric velocities. The
However, the largest increase (18% at mid-
upper limit of concentric velocity that is still capable
thigh level), as well as the by far highest rate of
of inducing hypertrophy is not known, but type 1
increase in quadriceps CSA (0.44% per day) for
fibre hypertrophy has been observed after training at
accommodating training, was noted in the study by
240°/s
[152]
and type 2 fibre hypertrophy after training
Rafeei,
[104]
who trained subjects with 5 sets of 10
at velocities as high as 300°/s.
[153]
While being quite
concentric muscle actions at 90% of the maximum
high compared with the cadence of conventional torque at 60°/s, three times per week for 6 weeks. An
interesting feature of the study of Rafeei
[104]
was that
resistance training, these velocities are still well be-
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244 Wernbom et al.
the subjects trained at the same absolute torque relatively high tensions. It is also possible that some
fast fibres are preferentially recruited during eccen-
throughout the study. Another notable feature was
tric actions and that this may occur at loads as low as
the generous rest periods, with 5 seconds between
25% of MVIA.
[158]
Thus, it may be too simplistic to
each concentric action and 120 seconds between
estimate the stress imposed on each muscle fibre
each set. The level of effort was probably high
merely by the magnitude of the external load.
enough to recruit most of the motor units, while the
In summary, although there may well exist a
high but not maximal force level and the generous
level of tension below which no hypertrophy occurs,
rest periods may have minimised muscle damage
the relationship between the training load and the
and fatigue of fast fibres, thus allowing the muscle
hypertrophic response is complex. Achieving re-
to hypertrophy already in the initial stages of train-
cruitment of the greatest possible number of motor
ing.
units in the target muscle(s) and making these motor
Regarding dynamic external resistance training,
units fire at high rates and for sufficient lengths of
the range of intensities that can produce hypertrophy
time are obvious prerequisites for inducing signifi-
is even more remarkable than in the case of accom-
cant hypertrophy. Still, it appears that maximal
modating resistance. Studies
[83,84]
have shown
loads are not necessary to ensure that these condi-
marked increases in CSA in response to loads as low
tions are met providing that the training is per-
as 20% of 1RM when the exercise has been com-
formed with close to maximum effort in at least one
bined with partial restriction of the blood flow by
of the sets. Thus, the results of this review support
means of thigh torniquets. Even so, consideration of
the typical recommendations with intensity levels of
the recruitment of motor units during fatiguing exer-
70–85% of maximum when training for muscle hy-
cise with low loads reveals that the results of the
pertrophy, but also show that marked hypertrophy is
studies of Takarada et al.
[83]
and Abe et al.
[84]
do not
possible at both higher and lower loads. However,
necessarily disprove the theory that tension is a
placing high mechanical stress on the working mus-
major determinant of the hypertrophic response. A
cle may result in local overtraining if the duration of
study by Greenhaff and co-workers
[157]
showed a
work is long. Some of the possible interactions
greatly increased rate of glycogenolysis in type 1
between the level of tension, duration of exercise,
fibres and a marked decline in force and near total
mode of exercise and muscle damage will be dis-
depletion of phosphocreatine in both fibre types
cussed in section 4.6. The impact of intensity in
during intermittent electrical stimulation of the
more advanced athletes remains poorly defined due
quadriceps with the blood flow occluded. In con-
to the lack of objective scientific data.
trast, the decline in force during the same protocol of
stimulation but with intact circulation was ascribed
4.3 Volume
almost solely to fatigue in type 2 fibres. Although
Greenhaff et al.
[157]
used electrical stimulation in-
A notable trend in the several types and modes of
stead of voluntary activation, their findings are of
strength training reviewed in this article was the
relevance for the development of fatigue under cir-
occurrence of a plateau in the hypertrophic adapta-
cumstances where the blood supply to the working
tions after a certain point of volume or duration of
muscle is limited, for example by a tourniquet and/
work had been reached. In some of the results, there
or by the raised intramuscular pressure during the
is even a suggestion of a decline when the volume or
continuously performed coupled concentric-eccen-
duration is extended beyond the point of the plateau.
tric muscle actions that conventional resistance
Again, it must be noted that no studies were found
training usually consists of. With a decline in force
that investigated the effects of 1 or 2 sets on muscle
in type 1 fibres, more type 2 fibres would have to be
CSA or muscle volume of the quadriceps or elbow
recruited and towards the end of each set, the re-
flexors. That said, figure 11, for the total repetitions
maining force-producing fibres could be exposed to
for DER training of the elbow flexors, suggests a
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Strength Training and Muscle Cross-Sectional Area 245
dose-response curve where greater gains in muscle muscle thickness were demonstrated after as little as
1 set of 8-12 repetitions of specific exercise per
mass are noted initially with increasing volume (or
muscle group. Because of this and given the relative
duration) of work, but with diminishing returns as
paucity of data, especially regarding the early part of
the volume increases further. Overall, moderate
the volume continuum (i.e. 1–20 total repetitions),
volumes (30–60 repetitions per session for DER
there is clearly a need for further research on the
training) appear to yield the largest responses.
impact of training volume on whole muscle CSA.
However, two notable exceptions
[125,126]
also ap-
This appears to be true for both previously untrained
pear in figure 11, which demonstrate that high rates
and well-trained individuals.
of growth can be achieved with a relatively small
However, recent data from Ronnestad et al.
[162]
number (12–14) of repetitions per session under
provide further support to the notion of a dose-
some circumstances. In the first of these studies,
[125]
response relationship between the training volume
very high loads (90–100% of 1RM) were used for
and the hypertrophic response of the quadriceps.
both the concentric and the eccentric phases and in
These authors reported superior increases in quadri-
the other study,
[126]
extremely high loads (progress-
ceps CSA for a total of 6 sets (11.3%) versus 2 sets
ing from 130 to 230% of 1RM) were used for the
(7.6%) of quadriceps exercise (two exercises of 1 or
eccentric phase. As can be seen in figure 10, the
3 sets each at 7–10RM) at an exercise frequency of
majority of the other datapoints were distributed
three times per week for 11 weeks. It deserves to be
between 60 and 90% of 1RM. A further example
noted that the subjects in this study received a prote-
demonstrating that significant hypertrophy can be
in supplement prior to each workout. Because it is
induced with a surprisingly small number of muscle
currently unknown how protein supplementation in-
actions at very high loads, at least in previously
teracts with training volume, these results may not
untrained subjects, can be found in a study by Haw-
necessarily apply to strength training that is per-
kins et al.,
[148]
who showed that a total of 9 maximal
formed without supplementation.
eccentric muscle actions was sufficient to induce
significant increases in thigh lean mass, while 12
4.4 Mode of Training and Type of
maximal concentric actions was not. Thus, the rela-
Muscle Action
tionship between volume and the hypertrophic re-
sponse may differ between different levels of torque
In the scientific literature relating to the area of
and/or types and modes of strength training. The
resistance training, one sometimes finds categoric
discrepancy between different studies in terms of the
statements such as ‘eccentric training produces the
volume needed to induce hypertrophy may, in part,
greatest muscle hypertrophy’. This review demon-
be related to differences in the total duration of
strates that given sufficient frequency, intensity and
muscle activity per session. In many studies, neither
duration of work, all three types of muscle actions
the velocity nor the duration of each repetition were
can induce significant hypertrophy at impressive
reported.
rates and that at present, there is insufficient evi-
To date, relatively few studies have directly com-
dence for the superiority of any mode and/or type of
pared the effects of different volumes of work on the
muscle action over other modes and types of train-
hypertrophic response as measured by scanning
ing in this regard. Using dynamic external resistance
methodology. These few studies
[146,159-161]
used less
training as an example, one would be tempted to
accurate measures of muscle mass rather than mus-
conclude that, if anything, pure eccentric training is
cle CSA or volume, or scanned only parts of the
actually inferior to both concentric and concentric-
muscle groups, and it is therefore difficult to com-
eccentric training, as judged by the degree and rate
pare these with studies in which whole muscle scans
of hypertrophy observed in the studies included in
were performed with MRI, CT or UL. However, in
this review. If one instead considers concentric and
two of these studies,
[159,160]
significant increases in
eccentric training with accommodating resistance,
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246 Wernbom et al.
maximal eccentric training has been slightly more If force is an important stimuli in resistance train-
effective than maximal concentric training in the ing, it follows that a certain level of torque must be
few studies that have directly compared these two reached for some minimum duration for significant
types of training. However, the hypertrophic re- hypertrophy to occur. In the pioneering study of
sponse has been modest in many of the studies Jones and Rutherford,
[55]
who compared pure con-
comparing the effects of pure concentric versus pure centric and eccentric regimens using a variable re-
eccentric training and this appears to be true both for sistance knee extension device, the authors noted
accommodating resistance and dynamic external re- that the subjects activation of the quadriceps was
sistance training studies. Thus, the protocols that high only near the position of full knee extension.
have been compared may not have been the best of Further inspection of their electromyogram data
each type. Again, it is noteworthy that both the suggests that the eccentric training was accompa-
largest total increase in CSA (18.4%) and the high- nied by slightly less activation than the concentric
est rate of increase in CSA (0.44% per day) for the training and also that the duration of high activity
quadriceps for the category of accommodating train- was shorter. Thus, it is possible that less than opti-
ing was noted for a pure concentric training mal internal force production and short total dura-
group.
[104]
This was also the second highest rate of tions of high activity contributed to the finding of no
increase for any mode of quadriceps training, sur- difference between the eccentric and concentric
passed only by the shorter study of Abe et al.
[84]
The training, and to the modest hypertrophy for both
findings of Rafeei,
[104]
of greater hypertophy at the protocols in their study. The eccentric and concen-
whole muscle level as well as at the muscle fibre tric exercise regimens in the studies of Housh et
level for near maximal concentric versus submax- al.
[68,69]
may have shared the same problem, as the
imal eccentric training, expanded on an almost iden- resistance in their device was greatest near full ex-
tical study from the same research group,
[163]
in tension. Nonetheless, the studies of Jones and Ruth-
which greater fibre hypertrophy was found for con- erford,
[55]
Smith and Rutherford
[62]
and Housh et
centric training when compared with eccentric train- al.
[68,69]
show that at least for the mode of dynamic
ing when both regimens were performed at the same external resistance training, the greater loads that are
torque level. possible with eccentric training (compared with
concentric training) do not necessarily translate into
The divergence in the results of concentric versus
greater gains in muscle size.
eccentric training between different modes (DER vs
accommodating resistance) may be due to differ- Among the accommodating modes, the isoiner-
ences in the characteristics of the resistance for each tial flywheel knee-extension model of Tesch and
mode. As discussed in the introduction, when using colleagues
[27,87,105,118]
has so far consistently induced
external resistance (e.g. free weights, weight ma- hypertrophy of the quadriceps CSA at high rates
chines), the torque is not necessarily optimally (0.17–0.22% per day). It is not immediately obvious
matched throughout the movement to the individu- why this mode seems to be more effective than most
al’s strength curve. Herzog et al.
[164]
calculated that of the isokinetic regimens that have also used maxi-
the internal forces of the three vastus muscles of the mal eccentric actions. In the flywheel study of Tesch
quadriceps are at their highest at knee angles of et al.,
[27]
the subjects were instructed to resist only
60–80° of flexion (full extension is defined here as gently during the first part of the eccentric action
0° of flexion), whereafter the forces drops to lower and then apply maximum force. The torque-angle
levels with decreasing angles of flexion. At 0–20° of curves in the same study
[27]
show that high eccentric
flexion, the forces are low, only 20–40% of maxi- forces were reached only during a rather short arc of
mum. Similarly, Ichinose et al.
[165]
reported that the 20–25°, from 65–90° of flexion. In contrast, dur-
force of the vastus lateralis was maximal at 70° of ing isokinetic eccentric exercise, maximum effort is
flexion. usually applied from the start and data
[166,167]
col-
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Strength Training and Muscle Cross-Sectional Area 247
lected at similar average velocities show that high ations can result in far greater peak loads than the
nominal load.
[129]
The significance, if any, of these
eccentric forces can be achieved through an arc of at
very high but momentary forces for the hypertrophic
least 40°. However, maximum eccentric efforts at
response remains to be explored. We speculate that
extended knee angles are often perceived as uncom-
differences in torque profile, torque-time integral
fortable.
[168]
In the isokinetic study of Seger et
and motor unit recruitment account for some of the
al.,
[102]
four of five subjects in the eccentric training
differences in the hypertrophy observed between
group had frequent complaints of knee pain during
studies where the training variables have been nomi-
the training, which may have affected the hyper-
nally similar. Also, if strenuous eccentric training is
trophic adaptations. Interestingly, Holder-Powell
performed at a high frequency, the hypertrophic
and Rutherford
[168]
showed that much of the discom-
response may become compromised. These interac-
fort associated with maximum isokinetic eccentric
tions will be discussed in greater detail in section
exercise could be avoided if the subjects started to
4.6.
resist later in the arc of motion, from 45° of flexion
In summary, all modes reviewed here seem capa-
instead of 15° of flexion. Also, the eccentric peak
ble of inducing marked hypertrophy, at least in the
torque was significantly higher when the range of
short term. This is not to say that some method or
motion was 45–95°, compared with 15-95° of flex-
combination of modes will not emerge as superior in
ion. It could be that the relatively low volumes and
the long term. The ideal proportions between the
short ranges of high-force eccentric exercise in the
different types of muscle actions are still a subject of
flywheel studies worked in favour of producing
debate rather than a scientific certainty.
hypertrophy, whereas the isokinetic-eccentric proto-
cols may have resulted in too much stress and strain
4.5 Rest Periods and the Role of Fatigue
on the tissues.
Other factors to consider when comparing the
Because too many studies did not report the rest
isokinetic and flywheel modes are the accelerations
periods between sets (and repetitions), we opted not
and decelerations that occur in the latter mode but by
to try to evaluate any trends. However, some elabo-
definition not in the former. It has been hypothesised
ration regarding the potential impact of rest periods
that accelerative and decelerative forces are impor-
is possible. Closely associated with rest periods is
tant components of the stimulus for muscle hyper-
the role of fatigue in strength training. Regarding
trophy in resistance training.
[169]
To date, there is
strength, some studies
[171,172]
have shown that short
little evidence to support this hypothesis. Collective-
rest periods between sets and/or repetitions are supe-
ly, the successes of both the dynamic, isokinetic and
rior to longer ones, whereas other studies
[173]
have
isometric modes in producing muscle hypertrophy
concluded that longer periods are superior to shorter
does not appear to support accelerations and/or de-
ones, while yet other studies
[174]
have reported no
celerations as being particularly important for the
difference. Upon closer examination, it appears that
hypertrophic response. However, although the angu-
when maximal or near-maximal efforts are used, it is
lar velocity in isokinetic training is controlled, the
advantageous to use long periods of rest. This is
fascicle velocity in the working quadriceps varies
logical in light of the well known detrimental effects
markedly through the range of motion.
[170]
Further-
of fatigue on force production and electrical activity
more, isokinetics usually involve a brief build up of
in the working muscle. If high levels of force and
maximum recruitment of motor units are important
speed before the isovelocity phase is reached and a
factors in stimulating muscle hypertrophy, it makes
short braking period after the isovelocity phase.
[170]
sense to use generous rest periods between sets and
Thus, from a muscle point-of-view, accelerations
repetitions of near-maximal to maximal efforts.
and decelerations occur even during ‘isokinetic’ ex-
ercise. It should also be noted that with weight-
It is interesting that for the accommodating and
based resistance training, accelerations and deceler-
isometric categories, the studies in which the highest
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248 Wernbom et al.
rates of muscle growth were found
[104,106]
did in- latter group trained with considerably less effort in
clude long rest periods. Furthermore, in the DER
comparison to the first group. The results showed a
training study
[92]
that reported the highest rate of
dramatic difference in the extent of hypertrophy in
CSA increase (0.26% per day), very long rest peri-
favour of the group that trained in a continuous
ods (10 minutes) between working sets were used,
manner (12.9% increase in quadriceps CSA), versus
but in this study the volume was periodised, which
the group that rested in the middle of each set (4.0%
may also have impacted on the results. It is also
increase in quadriceps CSA). The authors speculat-
worth noting that maximum isokinetic-concentric
ed that both increased recruitment of motor units
exercise performed with little rest between each
and a greater acute hormonal response could have
muscle action is associated with a marked decline in
contributed to the greater hypertrophy seen after the
peak torque during each working set, whereas little
continuous protocol. However, along with the in-
or no decline occurs during maximum eccentric
creased stress on the muscle with shorter rest peri-
exercise.
[175-177]
Hence, it can be hypothesised that if
ods at submaximal resistance, the potential for over-
the rest periods are too short during near-maximal
training may also increase. In a study by Folland and
concentric exercise, the training effects will be com-
colleagues,
[174]
conventional resistance training with
promised.
multiple sets to muscular failure and very short rest
Although eccentric exercise generally produces
periods (30 seconds) led to considerable delayed
little acute fatigue, it appears that it is dependent on
onset muscle soreness during the first week of train-
the training velocity (and probably also the work-to-
ing. With this type of training, caution with the
rest ratio), with faster eccentric velocities producing
training frequency and volume appears to be war-
less fatigue than slower velocities (see Tesch et
ranted.
al.
[175]
for a discussion). The difference in acute
The impact of rest periods may extend beyond
fatigue development between concentric and eccen-
the effects on fatigue and motor unit recruitment.
tric muscle actions and also between fast and slow
Using a rat muscle model, the research group of
eccentric muscle actions have obvious implications
Faulkner has, in a series of studies,
[178-180]
investigat-
for comparisons between these modes in regard to
ed the effects of electrical stimulation against the
training effects. On the other hand, when using
deleterious effects of denervation on muscle mass.
submaximal resistance, the size principle dictates
They showed that denervated muscle is sensitive to
that motor unit recruitment and firing rates are prob-
both the total number of muscle actions and the
ably far from maximal until the muscle is near
distribution of loading. For example, 100 muscle
fatigue or unless the repetitions are performed with
actions per day generated at a constant interval over
the intention to execute the movement very quickly.
24 hours was sufficient to maintain muscle mass and
The importance of exercising with near-maximal
force, but the same number of muscle actions dis-
effort when using submaximal resistance in conven-
tributed over just 4 hours per day (and consequently
tional strength training has been elegantly demon-
20 hours of rest in between) failed to maintain mass
strated by Goto and co-workers.
[85]
In their study,
and force. Although these findings may not necessa-
two groups of untrained subjects performed 5 sets of
rily extrapolate to intact innervated human muscle,
10 repetitions of dynamic knee extensions at a load
they show that skeletal muscle, at least under some
of 10RM (75% of 1RM), two times per week for 12
circumstances, is sensitive to both the total number
weeks. One group performed all 10 repetitions in
of muscle actions and the distribution of them. Fu-
each set in a continuous manner to muscular failure,
ture studies should examine the potential impact of
while the other group performed 5 repetitions and
both shorter (seconds) and longer (minutes, hours)
then rested for 30 seconds before performing the
rest periods on skeletal muscle hypertrophy and
remaining 5 repetitions. Thus, although the volume
was matched between the groups, the subjects of the hypertrophic signalling in this light.
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Strength Training and Muscle Cross-Sectional Area 249
4.6 Interactions Between Frequency, of 1.17 between the increase in CSA and thickness
Intensity, Volume and Mode
is applied to the elbow flexors in the study of Far-
thing and Chilibeck,
[151]
one arrives at an estimated
After acknowledging that the training volume
increase in CSA of 15% for the fast eccentric
seems to influence the hypertrophic response to a
training group.
certain extent, the question arises of what aspect of
The training groups of Farthing and Chilibeck
[151]
volume is the most important determinant of this
progressed from 2 sets of 8 repetitions to 6 sets of 8
response? Is it the total mechanical work performed
repetitions, resulting in an average total duration of
or is it the time-tension integral of the activity?
muscle activity per session of 22 and 132 seconds
Based on the available evidence, we suggest that the
for the fast and slow eccentric groups, respectively.
time-tension integral is a more important parameter
In the study of Shepstone et al.,
[138]
the progression
than the mechanical work output (force × distance).
was from 1 set of 10 repetitions to 4 sets of 10
The elbow flexor eccentric training studies of
repetitions and the corresponding average total
Refsnes,
[126]
Paddon-Jones et al.,
[38]
Farthing and
durations of muscle activity per session were 14 and
Chilibeck
[151]
and Shepstone et al.
[138]
provide in-
146 seconds for the fast and slow eccentric groups,
sight into some of the complex interactions that
respectively. We suggest that the slightly greater
takes place between the training variables of fre-
total duration for the fast group in Farthing and
quency, intensity, volume and mode of resistance
Chilibeck
[151]
versus Shepstone et al.
[138]
was re-
training. If one considers the last two of these stud-
sponsible for the greater hypertrophic response in
ies, one finds that the external work output (ex-
the former study. On the other hand, with the slow-
pressed as total number of repetitions × the torque
velocity protocols, the cumulative damaging effects
developed) was likely to be similar between the
of the long durations of maximum eccentric exercise
slow and fast eccentric groups because of the margi-
may have counteracted the hypertrophy so that this
nal difference in maximum torque between the slow
became less in comparison with the fast training.
and the fast velocities. In contrast, the total duration
The study of Refsnes,
[126]
using a dynamic constant
and the torque-time integral between the groups
resistance training model in which the eccentric
were vastly different, 6–10-fold greater for the
phase was overloaded (progressing from 130% to
slow groups compared with the fast groups. The
230% of 1RM during the time course of the study)
studies of Farthing and Chilibeck
[151]
and Shepstone
also attests to the effectiveness of short durations of
et al.
[138]
are difficult to compare with each other in
maximum eccentric exercise for inducing increases
terms of the degree of hypertrophy achieved because
in elbow flexor CSA. In this study, the volume was
different measures of muscle mass were used (mus-
carefully progressed from 2 sets of 2 repetitions to 5
cle thickness vs muscle CSA). Still, the hypertrophic
sets of 4 repetitions during the 8 weeks of the study,
response noted for the fast eccentric group appears
resulting in a maximum duration of 14–16 seconds
to be larger in the Farthing and Chilibeck study
[151]
of near-maximal eccentric work. The velocity in the
(13% increase in muscle thickness) than the 8.5%
eccentric phase was moderate, 80–90°/s. The con-
increase in CSA reported by Shepstone et al.
[138]
centric phase was loaded with only 30% of 1RM,
Because thickness measures only one dimension of
and the contribution of the concentric phase to the
the muscle, the increase in elbow flexor CSA was
hypertrophic response was therefore probably small.
likely to be greater than 13%. If the muscle grew
The subjects increased their elbow flexor CSA by
equally in width as it did in thickness, the result
21.5% (0.38% per day), an impressive increase es-
would be an increase in CSA of 27.7%. This scena-
pecially when considering the very brief duration of
rio seems unlikely, because a triceps training study
work.
by Kawakami et al.
[181]
showed that an increase of
The risk for overtraining with long durations of
31.7% in elbow extensor area was accompanied by
high-force eccentric exercise is supported by a study
an increase in thickness of 27.0%. If the same ratio
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250 Wernbom et al.
by Amiridis et al.,
[182]
who compared different On the other hand, studies by LaStayo and col-
leagues
[183,184]
using eccentric cycling at submax-
modes of training in a group of young elite female
imal intensities for long durations (20–30 minutes)
basketball players after a period of very strenuous
have shown very rapid and large gains in MFA
training for the knee extensors. During the first 12
(50–60%). Recently, a case report
[185]
was pub-
weeks, all subjects performed 8 sets of 8 concentric
lished that showed that marked hypertrophy is evi-
repetitions at 70% of 1RM and 8 sets of 8 eccentric
dent also at the whole muscle level after this type of
repetitions at 110% of 1RM in the leg press, 4
training. In these regimens, up to 1000–2000 ec-
sessions per week. At 12 weeks, the subjects had
centric muscle actions were performed during each
significantly reduced performances in both the leg
training session, three times per week. The absolute
press and the countermovement jump, indicating
intensity level was reported in watts, so it is difficult
that they were overtrained. During the second 12
to quantify the forces in terms of percentage of
weeks of training, the subjects were divided into
MVIA. Nevertheless, these studies
[183-185]
show that
three groups that performed different modes of re-
given careful and gradual progression of exercise
covery training, 4 sessions per week. The first group
intensity and duration, human skeletal muscle can
trained with 8 sets of 8 concentric repetitions at 70%
tolerate and adapt to prolonged submaximal-eccen-
of 1RM; the second group completed 4 sets of 8
tric exercise.
concentric repetitions at 70% of 1RM and 4 sets of 8
Overall, we feel that the trends observed in this
eccentric repetitions at 110% of 1RM; and the third
review are consistent with the model for training-
group performed 8 sets of 8 eccentric repetitions at
overtraining continuum proposed by Fry,
[186]
where
110% of 1RM. Compared with values from the first
the optimal training volume and also the volume
12 weeks overtraining, all groups increased their
threshold for overtraining decreases with increasing
performance in the leg press and the countermove-
intensity. The study of Abe et al.
[84]
is especially
ment jump, but only the pure concentric group noted
intriguing in this context because of the combination
significant increases in leg-press strength (39%),
of very low intensity and extremely high frequency.
isokinetic strength (11–43%) and vertical jump
To the best of our knowledge, no studies to date
(15%) in comparison with the pre-training values.
have investigated the effect of performing two
Although no morphological data was presented in
strength training sessions during the same day on
this study, it is likely that some degree of overtrain-
skeletal muscle protein synthesis, so it is not known
ing at the muscle level was responsible for the poor
whether there is any additional benefit in doing so
performance at 12 weeks. It is also interesting to
compared with performing just a single session. If
note that despite reduced total volume in compari-
the sensitivity of skeletal muscle protein synthesis to
son with the first 12 weeks, neither the pure eccen-
mechanical stimuli is regained during the same day
tric nor the combined concentric-eccentric groups
and if there is room for further elevations of the net
experienced any supercompensation in perform-
protein synthesis, then it would make sense to per-
ance, whereas the pure concentric group did. Thus, it
form more than one session per day. This could
would appear that moderate-force concentric train-
explain the results of H
¨
akkinen and Kallinen,
[61]
ing was better tolerated than high-force eccentric
although the effects of tapering down the volume
training, at least for the moderately high volumes
(and hence, the total stress per session imposed on
and the rather high training frequency used in this
the muscle) also remain a possibility. As pointed out
study. Taken together, the results of these studies
in the discussion concerning rest periods (section
support the common recommendation of using
4.5), mechanistic investigations concerning the ef-
somewhat lower frequencies and volumes for high-
fects of different distributions of loads and rest
force eccentric exercise than for conventional resis-
periods on skeletal muscle mass and/or intracellular
hypertrophic signalling are largely lacking. It is also
tance training.
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Strength Training and Muscle Cross-Sectional Area 251
uncertain whether the mechanosensitivity of skeletal was similar between the groups. Needless to say,
more research is needed regarding interactions be-
muscle decreases with long periods of strength train-
tween variables in both trained and untrained sub-
ing. Until these and other dose-response relation-
jects.
ships become more fully characterised, it will re-
Finally, a comment on the interactions between
main difficult to prescribe a proper ‘dosage’ of
strength and endurance training is warranted. It has
training for each mode of training and type of mus-
been recommended that both strength and endur-
cle action for the specific purpose of inducing hy-
ance training should be included in a well-rounded
pertrophy.
training programme.
[189]
The additive effects of
Regarding training for hypertrophy in already
strength and endurance training on various parame-
highly-trained individuals, there is at present insuffi-
ters of health status have been shown in several
cient data to suggest any trends in the dose-response
studies.
[190-192]
Recently, it has been demonstrated
curves for the training variables. It has been suggest-
that while strength training by itself can lead to
ed by some authors
[187]
that the volume needed to
increased arterial stiffness, this negative effect can
induce optimal gains in strength, increases with
be offset if endurance training is performed concur-
training status, so that advanced trainers and elite
rently.
[193]
From a strength training point of view,
athletes will have to perform far more sets (10 sets
there is an interest in how to train concurrently
per muscle group) than untrained and recreational
without affecting strength and hypertrophy nega-
lifters (4–5 sets per muscle group). Other authors
tively. It has been suggested that strength training
emphasise the importance of load and the type of
should be performed first, in order not to compro-
muscle action. Refsnes
[188]
has reported preliminary
mise the quality of the strength-training session.
[194]
findings from unpublished studies, which indicate
However, this order may not necessarily be the best
that very well-trained athletes respond to eccentric
choice for inducing increases in muscle mass.
overload training with greater hypertrophy than af-
Deakin
[195]
investigated the impact of the order of
ter conventional training. Recently, a study by
exercise in combined strength and endurance train-
Vikne and colleagues
[137]
demonstrated significantly
ing and reported that gene expression associated
larger increases in elbow flexor area in well-trained
with muscle hypertrophy responded more strongly
individuals after pure eccentric training (11% in-
when cycling was performed before strength train-
crease) than after concentric training (3% increase).
ing, instead of vice versa. Interestingly, in the study
It should be noted that the volume was not equalised
of Sale et al.,
[111]
performing cycling first seemed to
between the groups and it also seems likely that the
induce the greatest increase in muscle area. Still,
total duration of work was markedly longer for the
because the lack of studies investigating the effects
eccentric group, thus resulting in large differences in
of the order of exercise in concurrent training on
time-tension integral between the protocols. Hence,
hypertrophy, no firm conclusions can be drawn on
although the results suggest a clear superiority of
this issue.
pure eccentric exercise versus pure concentric exer-
cise for inducing hypertrophy in well-trained sub-
4.7 Time Course of Muscle Hypertrophy
jects, other variables cannot be ruled out as contrib-
uting factors. Seemingly at odds with the observa-
Strength gains as a result of a period of resistance
tions of Refsnes
[188]
and Vikne et al.,
[137]
training are usually attributed to two major factors:
Brandenburg and Docherty
[133]
showed no differ-
(i) neural adaptations; and (ii) hypertrophy.
[196]
Until
ence in muscle CSA after eccentric-overload train-
recently, the prevailing opinion has been that neural
ing for the elbow flexors and the elbow extensors
adaptations play the dominant role during the first
compared with conventional training. In their
6–7 weeks of training, during which hypertrophy is
study,
[133]
coupled concentric-eccentric repetitions
usually minor. However, as noted by Staron and co-
were performed in both groups and the total volume
workers
[196]
and by Sale,
[197]
it appears that the hy-
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252 Wernbom et al.
pertrophy process begins earlier than this, as trends that the majority of the increase took place during
the first 10 weeks of training.
for increased fibre CSAs can be observed at 2 weeks
into the training period. In the studies of Mayhew et
Little is also known about how different training
variables and modes interact with the length of the
al.
[163]
and Rafeei,
[104]
significant increases in fibre
training period. In some strength-training studies,
CSA (type 1 = 12–14%; type 2 = 26–28%) were
the increase in muscle volume is delayed, while in
observed for the concentric training groups as early
others, the rate of growth is rapid. We speculate that
as 4 weeks into the training. In the latter study,
[104]
less-damaging training modes may allow the hyper-
further hypertrophy had occurred at 6 weeks, which
trophy response to start earlier. Regimens that in-
was also manifested at the whole muscle level
clude eccentric muscle actions, especially those in-
(18% increase in quadriceps CSA at mid-thigh
volving maximal effort, appear to require a careful
level). In the study of Abe et al.,
[84]
significant
initiation and progression of training to avoid mus-
increases in muscle volume were noted after just 2
cle damage and muscle protein breakdown. In line
weeks and several other investiga-
with the results of Foley et al.,
[200]
who noted a long-
tions
[13,27,54,87,105,118,128]
have also demonstrated sig-
lasting decrease in elbow flexor muscle volume after
nificant hypertrophy at the whole muscle level after
an acute session of high-force eccentric exercise,
short periods of training (3–5 weeks). Thus, there is
Willoughby et al.
[201]
found decreased myofibrillar
now plenty of evidence that significant hypertrophy
protein content in muscle biopsies taken from the
can take place early on given proper frequency,
vastus lateralis after an acute session of 70 near-
intensity and volume of training.
maximal eccentric actions for the knee extensors.
Based on the observation of positive muscle-
This decrease was accompanied by increases in cas-
protein balance after an isolated session of resis-
pase 3 activity and in the expression of ubiquitin,
tance exercise, Phillips
[198]
has proposed that a gain
which the authors interpreted as indicating that
in active force-producing myofibrillar proteins
apoptosis and increased proteolysis had occurred in
could occur after a single strength-training session
the exercised muscle. They also reported a repeated
and that this increase may take place without a
bout effect for most of the parameters after a second
change in fibre CSA. In line with this idea, Wil-
session of an identical eccentric protocol. Neverthe-
loughby and Taylor
[199]
reported an increase in my-
less, a trend towards decreased myofibrillar content
ofibrillar content in muscle biopsies obtained from
was evident even after the second session, although
previously untrained young men after just three
this was not significant and certainly of a smaller
strength-training sessions, with sessions separated
magnitude than after the first session. In contrast, in
by 48 hours of rest. As argued by Phillips,
[198]
the
the study of Willoughby and Taylor,
[199]
where a
idea that early gains in strength are due exclusively
conventional resistance-training model for the quad-
to neural adaptations seems doubtful. Judging from
riceps was employed, the myofibrillar content ap-
the studies included in this review, the hypertrophy
peared to increase from the very first workout,
process actually seems to be most rapid during the
reaching significance after the second session.
first 6 weeks, after which the rate declines slowly.
Clearly, more research into the time course of the
Because the majority of studies have only investi-
hypertrophic process is needed, especially with ref-
gated a time period of up to 12 weeks, it is difficult
erence to the effects of different regimens and
to assess how the rate of protein accretion is affected
modes.
by longer periods of training. A study by Sale et
al.
[112]
suggests that relatively high rates of increase
4.8 Hypertrophic Response of the
in muscle CSA (0.22–0.24% per day) may be possi-
Quadriceps versus the Elbow Flexors
ble to maintain for periods of up to 20 weeks, but
unfortunately no mid-point data were available from
It has long been recognised that some muscles are
this investigation. Therefore, it cannot be excluded
very responsive to the stimulus of strength training,
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Strength Training and Muscle Cross-Sectional Area 253
while others seem more stubborn. One explanation eral excellent reviews
[205-208]
and original investiga-
to this phenomenon could be that muscles that are
tions
[91,209-213]
on various aspects of this topic are
frequently used in everyday activities are already in
available. However, a brief discussion of some of
a trained state, thus leaving less room for improve-
the physiological stimuli occurring during resistance
ments in strength and size. For example, the soleus
training that may trigger the hypertrophic pathways
muscle appears to be relatively unresponsive to re-
is relevant. Over 30 years ago, it was suggested by
sistance exercise in comparison with the vastus
Goldberg and co-workers
[214]
that increased tension
lateralis and the biceps brachii.
[202]
Regarding the
development (either passive or active) is the critical
latter two muscles, it is commonly held that the
event in initiating compensatory growth. MacDou-
elbow flexors are in a less-trained state than the
gall
[215]
noted that the loading of the muscle must be
quadriceps.
[128,203]
Studies where the hypertrophic
very high in order to result in hypertrophy, but that
response of the quadriceps and the elbow flexors to
the total duration during which the muscle develops
similar training regimens have been directly com-
tension also affects the magnitude of the hypertro-
pared tend to support this theory.
[48,66,204]
The trends
phy response. He supported this observation with
reported in this review for conventional resistance
the results of the study of Sale and colleagues,
[125]
training for the quadriceps versus the elbow flexors
who showed a tendency for training with 6 sets of
lend support to this observation, as the CSA of the
10–12RM to result in larger increases in elbow
elbow flexors tended to increase at a greater rate
flexor muscle CSA than training with 6 sets of
(0.20% per day) than the quadriceps (0.11% per
1–3RM (33% vs 24%).
day). Further support comes from a study by Turner
Two studies by Martineau and Gardiner
[216,217]
and co-workers,
[203]
who found marked hypertrophy
have provided insight into how different levels of
in the elbow flexors (24% increase in CSA) in
force and different durations of tension may affect
response to endurance training for the upper limb
hypertrophic signaling in skeletal muscle. Using rat
(arm cycling to exhaustion for 30 minutes, five
muscle preparations, these authors noted that
times per week for 6 weeks), while leg cycling at the
mechanically sensitive pathways reacted in a dose-
same relative intensity and duration had negligible
dependent manner to the level of force, so that larger
effects on the mass of the lower limb. Notably, the
increases in intracellular signaling were seen after
rate of CSA hypertrophy for the elbow flexors ob-
eccentric actions when compared with isometric and
served in this study (0.57% per day) surpasses all
concentric actions.
[216]
In a follow-up study,
[217]
they
strength-training studies included in this review,
showed that the same pathways were also sensitive
except that of Narici and Kayser.
[128]
The differences
to the time-tension integral in a dose-dependent
between various muscle groups in the physiological
manner. Interestingly, this was the case regardless of
response to similar training regimens warrants some
whether the total duration was distributed into a few
caution in generalising findings from one muscle
long durations of stretch or many short ones. Also,
group to another. Future investigations should study
the rate of stretch had no effect on these pathways.
whether the dose-response relationships differ be-
In the latter study,
[217]
they remarked that both peak
tween the elbow flexors and the quadriceps in regard
tension and time-tension integral must be included
to the major training variables.
in the modelling of the mechanical stimulus re-
sponse of skeletal muscle. Some of the pathways
4.9 The Stimulus for Muscle Hypertrophy in
that are now recognised as crucial for the hyper-
Strength Training
trophic response were not assessed in the studies of
Martineau and Gardiner,
[216,217]
and little is currently
It is beyond the scope of this article to discuss in
known about the response of these pathways to the
any detail the pathways or networks of intracellular
variables of peak tension and time-tension integral.
signals leading to hypertrophy as a result of a period
One of these is the phosphatidylinositol-3 kinase/
of increased loading of the muscle(s) involved. Sev-
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254 Wernbom et al.
protein kinase B/mammalian target of rapamycin tion (e.g. temporarily increased Ca
2+
levels in the
cytosol, metabolite accumulation, ischaemia and
pathway,
[205-208]
which has several downstream
acute hormonal changes) may also act as signals for
targets, among them the signaling molecule p70 S6
adaptation and interactions between these and
kinase (p70S6K). A recent study by Eliasson et
mechanically-induced signaling seem plausible. The
al.
[218]
showed that the phosphorylation of p70S6K
potential role of acute hormonal responses has been
in the human quadriceps 2 hours after resistance
reviewed by Kraemer and Ratamess.
[221]
exercise was greater after a total of 24 maximal-
Apart from mechanical forces, growth factors
eccentric actions compared with 24 maximal-con-
and hormones, another exercise-related stimuli that
centric actions and to 24 submaximal eccentric ac-
has been shown to affect the hypertrophic signaling
tions. However, this was in the absence of nutrition-
in skeletal muscle (as assessed by phosphorylation
al supply. In contrast, Cuthbertson and col-
of p70S6K) is heat stress.
[222]
Interestingly, both in
leagues
[219]
demonstrated similar increases in
cultured muscle cells and in skeletal muscle, heat
p70S6K and muscle protein synthesis after eccentric
stress and mechanical stretch has been shown to
and concentric exercise. Importantly, in this study
interact so that protein expression and concentration
the subjects received protein and carbohydrate sup-
is higher after a combination of the two stimuli than
plementation immediately post-exercise. Another
either alone.
[223,224]
These authors suggested that a
difference is that a much greater volume of work
stress-induced heat-shock response may modulate
was performed compared with the study of Eliasson
the exercise-induced adaptations of skeletal mus-
et al.
[218]
cles, for example when combining vascular occlu-
Based on the data reviewed in this paper, we
sion with resistance exercise. If an interaction be-
speculate that hypertrophic signalling in human
tween heat stress and mechanical stimuli occurs
skeletal muscle is very sensitive to the magnitude of
during strength training with restricted blood flow, it
tension developed in the muscle. Hence, for very
could, at least in part, explain the success of low-to-
short durations of work, the increase in muscle size
moderate intensity training during these conditions
will be greater for maximal-eccentric exercise than
in inducing hypertrophy,
[83,84,131]
even in highly-
for maximal-concentric exercise of similar dura-
trained athletes.
[76,225]
tions, as in the studies of Farthing and Chilibeck
[151]
and Hawkins et al.
[148]
The response is presumably
4.10 Suggestions for Future Research
also dependent on the total duration of work and
increases initially with greater durations. Thus, both
The trends observed in this review could serve as
short durations of maximal eccentric exercise and
a starting point for experiments aiming to establish
somewhat longer durations of concentric, isometric
efficient models of training for the purpose of gain-
and conventional dynamic resistance exercise can
ing and/or preserving muscle mass. Major chal-
result in impressive increases in muscle volume.
lenges for future research are to isolate the impact of
However, especially with maximal eccentric exer-
each of the resistance training variables and to in-
cise, damage also seems to come into play as the
vestigate the interactions between them, as well as
duration of work increases even further and the
the effects of various training strategies (e.g. peri-
acute and/or cumulative damage may eventually
odization, tapering, changes in type and mode of
overpower the hypertrophic process. This could be
exercise in order to ‘shock’ the muscles). We also
an explanation for the modest hypertrophy reported
recommend that future investigations should de-
in several isokinetic training studies where the ec-
scribe the exercise protocols in greater detail than
centric component has been maximal and of moder-
has generally been the case up until recently. Conse-
ate-to-long total durations. As discussed by Rennie
quently, variables such as speed, range and duration
and colleagues
[205]
and Jones and Folland,
[220]
other
of each repetition and rest periods between repeti-
physiological events associated with muscle activa-
tions and sets should also be reported in addition to
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Strength Training and Muscle Cross-Sectional Area 255
the commonly recognised variables of frequency, er, because EMS involves motor-unit firing patterns,
intensity, volume and mode of exercise.
which are usually very different from those occur-
ring in voluntary exercise, findings from such stud-
To date, the vast majority of the research con-
cerning the effects of manipulating training vari- ies may not necessarily apply to voluntary strength
ables have been carried out using DER training. For
training.
example, we were unable to locate any accommo-
As noted in section 2.1, investigations concern-
dating training study that directly compared the ef-
ing very well-trained individuals are largely lacking,
fects of different volumes on the hypertrophic re-
as are studies extending for longer than the typical
sponse. Because the accommodating training modes
8–12 weeks. Because of this, the knowledge regard-
can induce hypertrophy at rates comparable to those
ing the dynamics of the hypertrophy process past
of conventional weight training, and because the
this point is limited. In short-term studies, large
training parameters are easily standardised, these
increases in the training loads for lower-body exer-
modes are well suited for experiments designed to
cises such as squats, leg presses and knee extensions
provide insight into the nature of the dose-response
are often reported, sometimes on the order of
relationships.
100–200%.
[18,55,196]
Since the gain in quadriceps
In humans, electromyostimulation (EMS) has
muscle volume during the same time period rarely
been proven to result in increases in muscle volume
exceeds 15%, the stress per unit of muscle area
comparable to those seen after voluntary strength
should increase by almost as much as the increase in
training. Since EMS bypasses the CNS, the level of
training weight. The significance of the large in-
activation of a particular muscle group can be
crease in the stress on the muscles and its interac-
standardised. Combining EMS with isokinetic dyna-
tions with the volume and frequency of training in
mometry could provide an opportunity to gain fur-
terms of the hypertrophic response and the risk for
ther insight into many of the issues discussed in this
overtraining remains to be explored. Although not
review, such as the effects of the level of torque, the
discussed in this article, the issue of dose-response
type of muscle action (concentric vs isometric vs
eccentric) and the total duration of activity. Howev- effects needs to be adressed in the training of other
Table I. Recommendations for dynamic external resistance training (e.g. weight-based resistance) for hypertrophy
Moderate load slow-speed training Conventional hypertrophy training Eccentric (ecc) overload training
Muscle action Con and ecc Con and ecc Ecc (con = optional)
Exercise Single and/or multiple joint Single and/or multiple joint Single and/or multiple joint
Load 50% of 1RM 8–10RM (range: 6–12) Ecc = >105% of 1RM
75–80% of 1RM Con = 60-75% of 1RM
Repetitions 8–14 to muscular failure 8–10 to muscular failure or near 4–6
Sets 1–3 per exercise 1–3 per exercise 1–5 per exercise
Progression from 1 to 3–4 sets in Progression from 1–2 to 3–6 sets Progression from 1–2 to 3–5 sets in
total per muscle group in total per muscle group total per muscle group
Velocity and duration Slow Moderate Slow/moderate
per repetition Ecc = 2–3 seconds Ecc = 1–2 seconds Ecc = 2–4 seconds
Con = 2–3 seconds Con = 1–2 seconds Con = 1–2 seconds
Rest between sets 30–60 seconds 60–180 seconds 120–180 seconds
Frequency 2–3 sessions per muscle group/ 2–3 sessions per muscle group/ 1–3 sessions per muscle group/week
week week
Comments Suitable training method for These recommendations are for Mainly for advanced to elite athletes.
beginners and individuals who novice to moderately trained Progressive but careful increase of
cannot tolerate high forces individuals. Well trained athletes the load and volume for the eccentric
may need increased variation in phase
intensity and volume
Con = concentric; RM = repetition maximum.
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256 Wernbom et al.
Table II. Recommendations for accommodating training for hypertrophy
Moderately fast concentric (con) Slow concentric training Accommodating eccentric (ecc)
training overload
Mode Isokinetic or hydraulic Isokinetic or hydraulic Isokinetic or isoinertial flywheel
Muscle actions Con Con Ecc and con (con is optional in
isokinetics)
Exercise Single and/or multiple joint Single and/or multiple joint Single and/or multiple joint
Effort
a
90100% 90% Ecc = up to 100%
Con = up to 100%
Repetitions 1015 10 68
Sets 36 per exercise 35 per exercise 15 per exercise
Progression from 3 to 46 sets in Progression from 3 to 5 sets in Progression from 12 to 45 sets
total per muscle group total per muscle group in total per muscle group
Velocity 120240°/s 4560°/s 4560°/s
Rest between repetitions 12 seconds, 5 seconds, 05 seconds,
and sets, respectively 60120 seconds 120 seconds 120 seconds
Frequency 35 sessions per muscle group/ 3 sessions per muscle group/week 2 sessions per muscle group/week
week
a indicates level of torque in relation to the maximum possible torque at the specified velocity.
populations, such as the elderly and individuals re- to hypertrophy further in relative terms than a previ-
covering from sports injuries.
ously untrained muscle. Conversely, a muscle that
has atrophied because of disuse or detraining has a
4.11 Limitations
large growth potential and merely getting it back to
its previous level will represent an increase in mus-
We recognise that it is obviously very difficult to
cle volume if the atrophied state is taken as a base-
separate the impact of each training variable from
line. Thus, even slight variations in training status
the effects of the other training variables. For exam-
may affect the hypertrophic response to a given
ple, if one increases the training load (percentage of
resistance training regimen. Also, the method of
1RM) in conventional weight training, it will also
measuring muscle volume or CSA may influence
affect the volume of training, unless this is compen-
the results. With earlier scanning techniques, the
sated for by increasing the number of sets per-
anatomical CSA of the muscle was measured with-
formed. Furthermore, we acknowledge that the main
out correcting for intramuscular fat. Recent methods
objective of many of the studies included in this
of MRI and CT allow for measurements of intersti-
review was not necessarily to maximise the hyper-
tial fat, as well as muscle, and consequently for
trophic response and that the motivational level of
calculation of adipose tissue-free muscle.
[227]
In
the subjects may well have differed considerably
young healthy subjects, the anatomical muscle area
between different studies. Closely associated with
is only slightly larger than adipose tissue-free mus-
motivation is whether the training is performed
cle area.
[227]
Hence, any increase in muscle volume
under supervision or not. Direct supervision of the
as a result of strength training will mainly reflect an
workout has been shown to result in superior in-
increase in adipose tissue-free muscle mass. There-
creases in strength when compared with un-
fore, the data from the studies included in this re-
supervised training.
[226]
The level of supervision
view were pooled irrespective of the muscle-scan-
during training varied among the studies included in
ning method used. However, because of the factors
this review.
discussed here and the many other confounding
Apart from the training regimen, the training
factors that inevitably are present when summaris-
status is also likely to have an impact on the hyper-
ing and comparing the results of many different
trophic response. Theoretically, a muscle that is
already somewhat hypertrophied has less potential studies, the dose-response trends and recommenda-
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Strength Training and Muscle Cross-Sectional Area 257
tions outlined in the present review should be re- tion stand
[3]
and by Kraemer and Ratamess.
[1]
We
garded as tentative.
also agree with these authors on the importance of
progression and individualisation of the exercise
prescription. Regarding progression, we recommend
4.12 Training Implications
and Recommendations
low volumes (e.g. 1–2 sets) in the initial stages of
training, when performing eccentric-muscle actions,
Preliminary recommendations for each mode are
because low volumes have been shown to be suffi-
given in table I, table II and table III. These are
cient to induce hypertrophy in the early stages of
based on the evidence outlined in this article, as well
training and because exercise adherence may be
as on training protocols that have been shown to
improved if the workout is relatively brief. Also,
increase muscle mass. However, the tables should
avoiding unnecessary damage may allow hypertro-
not be interpreted as stating that all modes and
phy to take place earlier. As the individual adapts to
methods are equally effective in increasing muscle
the stimulus of strength training, the overall volume
mass. Rather, the aim is to summarise different
and/or intensity may have to be gradually increased
methods that may be suitable in different situations
to result in continued physiological adaptations and
and for specific populations. For example, fatiguing,
other strategies (e.g, periodisation) can also be intro-
low-to-moderate load, slow-speed resistance train-
duced if even further progress is desired.
ing
[75,88,92,130]
has potential applications for the reha-
In this context, it is essential that the trainer or
bilitation of patients for whom the high forces of
therapist is aware of possible interactions between
conventional heavy-resistance exercise are contrain-
the training variables and how these, in turn, interact
dicated. For patients who can tolerate relatively high
with the exercise tolerance of the individual. For
forces, but for whom the metabolic and cardiovascu-
example, a training volume that is appropriate at a
lar demands of traditional strength training are too
frequency of two sessions per muscle group per
severe, pure eccentric exercise may be an alternative
week may become excessive at three sessions per
because of the low energy demands of this type of
week. Conversely, a volume that is sufficient at
exercise.
[183]
Our recommendations for conventional
three sessions per week may be less than optimal at
hypertrophy training are similar to those presented
in the American College of Sports Medicine posi- two sessions per week. The workout structure (e.g.
Table III. Recommendations for isometric training for hypertrophy
Low-intensity isometric training High-intensity isometric training Maximum-intensity isometric
training
Exercise selection Single and/or multiple joint Single and/or multiple joint Single and/or multiple joint
Torque level 3050% of MVIA 7080% of MVIA 100% of MVIA
Repetitions 1 1 10
Sets 26 per exercise 26 per exercise 13 per exercise
Progression from 2 to 46 sets in Progression from 2 to 46 sets Progression from 1 to 3 sets in
total per muscle group in total per muscle group total per muscle group
Duration per repetition 4060 seconds, and to muscular 1520 seconds, and to muscular 35 seconds
failure during the final 12 sets failure during the final 12 sets
Rest between repetitions 3060 seconds 3060 seconds 2530 seconds,
and sets, repectively 60 seconds
Frequency 34 sessions per muscle group/ 34 sessions per muscle group/ 3 sessions per muscle group/week
week week
Comments Suitable for individuals who cannot Suitable for individuals who Care should be taken to avoid
tolerate high forces and with cannot tolerate near-maximal excessive breath-holding and very
restricted range of movement due forces high blood pressures
to pain and/or injury
MVIA = maximal voluntary isometric action.
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258 Wernbom et al.
whole-body workout versus single muscle-group trained subjects or for training studies extending for
training) also has a direct bearing on the appropriate several months, the dose-response trends and the
dosage of training. Table I, table II and table II are hypertrophic effects of different modes and types of
intended as guidelines for single muscle-group strength training may be very different. The same
training. If whole-body workouts are performed, the may well be true for other populations, such as
volume of specific work per muscle group may have elderly and injured individuals.
to be reduced so that the overall volume does not
become excessive. For further discussion on the Acknowledgements
topic of workout design, we refer to the paper of
No sources of funding were used to assist in the prepara-
Kraemer and Ratamess.
[1]
tion of this review. The authors have no conflicts of interest
that are directly relevant to the content of this review.
5. Conclusions
References
This review demonstrates that several modes of
1. Kraemer WJ, Ratamess NA. Fundamentals of resistance train-
training and all three types of muscle actions can ing: progression and exercise prescription. Med Sci Sports
Exerc 2004; 36: 674-88
induce hypertrophy at impressive rates and that, at
2. Escamilla R, Wickham R. Exercise-based conditioning and
present, there is insufficient evidence for the superi-
rehabilitation. In: Kolt GS, Snyder-Mackler L, editors. Physi-
cal therapies in sports and exercise. London: Churchill Living-
ority of any mode and/or type of muscle action over
stone, 2003: 143-64
other modes and types of training. That said, it
3. Kraemer WJ, Adams K, Cafarelli E, et al. American College of
appears that exercise with a maximal-eccentric com-
Sports Medicine Position Stand: progression models in resis-
tance training for healthy adults. Med Sci Sports Exerc 2002;
ponent can induce increases in muscle mass with
34: 364-80
shorter durations of work than other modes. Some
4. Rhea MR, Alvar BA, Burkett LN, et al. A meta-analysis to
determine the dose response for strength development. Med
evidence suggests that the training frequency has a
Sci Sports Exerc 2003; 35: 456-64
large impact on the rate of gain in muscle volume for
5. Rhea MR, Alvar BA, Burkett LN. Single versus multiple sets for
shorter periods of training. Because longer studies
strength: a meta-analysis to address the controversy. Res Q
Exerc Sport 2002; 73: 485-8
using relatively high frequencies are lacking, it can-
6. Peterson MD, Rhea MR, Alvar BA. Maximizing strength devel-
not be excluded that stagnation or even overtraining
opment in athletes: a meta-analysis to determine the dose-
response relationship. J Strength Cond Res 2004; 18: 377-82
would occur in the long term. Regarding intensity,
7. Rhea MR, Alderman BL. A meta-analysis of periodized versus
moderately heavy loads seem to elicit the greatest
nonperiodized strength and power training programs. Res Q
gains for most categories of training, although ex-
Exerc Sport 2004; 75: 413-22
8. Wolfe BL, LeMura LM, Cole PJ. Quantitative analysis of sin-
amples of very high rates were noted at both very
gle- vs multiple-set programs in resistance training. J Strength
low and very high intensities when the sets were
Cond Res 2004; 18: 35-47
performed with maximum effort or taken to muscu-
9. Atha J. Strengthening muscle. Exerc Sports Sci Rev 1981; 9:
1-73
lar failure. Thus, achieving recruitment of the great-
10. Behm DG. Neuromuscular implications and applications of
est number of muscle fibres possible and exposing
resistance training. J Strength Cond Res 1995; 9: 264-74
11. H
¨
akkinen K. Neuromuscular adaptation during strength train-
them to the exercise stimulus may be as important as
ing, aging, detraining, and immobilization. Crit Rev Phys
the training load per se. For the total volume or
Rehab Med 1994; 6: 161-98
duration of activity, the results suggest a dose-re-
12. Fry AC. The role of resistance exercise intensity on muscle fibre
adaptations. Sports Med 2004; 34: 663-79
sponse curve characterised by an increase in the rate
13. Choi J, Takahashi H, Itai Y, et al. The difference between effects
of growth in the initial part of the curve, which is
of ‘power-up type’ and ‘bulk-up type’ strength training exer-
followed by the region of peak rate of increase, cises: with special reference to muscle cross-sectional area,
muscular strength, anaerobic power and anaerobic endurance.
which in turn is followed by a plateau or even a
Jpn J Phys Fitness Sports Med 1998; 47 (1): 119-29
decline.
14. Masuda K, Choi JY, Shimojo H, et al. Maintenance of my-
oglobin concentration in human skeletal muscle after heavy
It is recognised that the conclusions drawn in this
resistance training. Eur J Appl Physiol 1999; 79: 347-52
paper mainly concern relatively short-term training
15. Schmidtbleicher D, Buehrle M. Neuronal adaptation and in-
in previously untrained subjects and that in highly- crease of cross-sectional area studying different strength train-
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
Strength Training and Muscle Cross-Sectional Area 259
ing methods. In: Jonsson GB, editor. Biomechanics X-B, vol- sion in sedentary and highly skilled humans. Eur J Appl
ume 6-B. Champaign (IL): Human Kinetics, 1987: 615-20 Physiol 1996; 73: 149-56
16. Stone MH, O’Bryant HS. Weight training: a scientific approach.
36. MacDougall JD. Adaptability of muscle to strength training: a
Minneapolis (MI): Bellweather press, 1987
cellular approach. In: Saltin B, editor. Biochemistry of Exer-
cise VI. Champaign (IL): Human Kinetics, 1986: 501-13
17. Poliquin C. Five steps to increasing the effectiveness of your
strength training program. Natl Strength Cond Assoc J 1988;
37. Hortobagyi T, Katch FI. Eccentric and concentric torque-veloc-
10: 34-9
ity relationships during arm flexion and extension: influence of
18. Campos GE, Luecke TJ, Wendeln HK, et al. Muscular adapta-
strength level. Eur J Appl Physiol 1990; 60: 395-401
tions in response to three different resistance-training regi-
38. Paddon-Jones D, Leveritt M, Lonergan A, et al. Adaptation to
mens: specificity of repetition maximum training zones. Eur J
chronic eccentric exercise in humans: the influence of contrac-
Appl Physiol 2002; 88: 50-60
tion velocity. Eur J Appl Physiol 2001; 85: 466-71
19. Reeves ND, Maganaris CN, Narici MV. Ultrasonographic as-
39. Atherton PJ, Babraj J, Smith K, et al. Selective activation of
sessment of human skeletal muscle size. Eur J Appl Physiol
AMPK PGC-1alpha or PKB-TSC2-mTOR signaling can ex-
2004; 91: 116-8
plain specific adaptive responses to endurance or resistance
20. Miyatani M, Kanehisa H, Kuno S, et al. Validity of ultraso-
training-like electrical muscle stimulation. FASEB J 2005; 19:
nograph muscle thickness measurements for estimating muscle
786-8
volume of knee extensors in humans. Eur J Appl Physiol 2002;
40. Deschenes MR, Kraemer WJ. Performance and physiologic
86: 203-8
adaptations to resistance training. Am J Phys Med Rehabil
21. Ikai M, Fukunaga T. A study on training effect on strength per
2002; 81 (11 Suppl.): S3-16
unit cross-sectional area of muscle by means of ultrasonic
41. Maughan RJ, Watson JS, Weir J. Muscle strength and cross-
measurement. Eur J Appl Physiol 1970; 28: 173-80
sectional area in man: a comparison of strength-trained and
22. Knuttgen HG, Komi PV. Basic considerations for exercise. In:
untrained subjects. Br J Sports Med 1984; 18: 149-57
Komi PV, editor. Strength and power in sport. 2nd ed. Oxford:
42. Narici MV, Roi GS, Landoni L, et al. Changes in force, cross-
Blackwell scientific publications, 2003: 3-7
sectional area and neural activation during strength training
23. Fleck SJ, Kraemer WJ. Designing resistance training programs.
and detraining of the human quadriceps. Eur J Appl Physiol
2nd ed. Champaign (IL): Human Kinetics, 1997
1989; 59: 310-9
24. Grimby G. Clinical aspects of strength and power training. In:
43. Narici MV, Hoppeler H, Kayser B, et al. Human quadriceps
Komi PV, editor. Strength and power in sport. Oxford:
cross-sectional area, torque and neural activation during 6
Blackwell scientific publications, 1992: 338-54
months strength training. Acta Physiol Scand 1996; 157:
25. O’Hagan FT, Sale DG, MacDougall JD, et al. Comparative
175-86
effectiveness of accommodating and weight resistance training
44. Aagaard P, Andersen JL, Dyhre-Poulsen P, et al. A mechanism
modes. Med Sci Sports Exerc 1995; 27: 1210-9
for increased contractile strength of human pennate muscle in
26. Baker D, Wilson G, Carlyon B. Generality versus specificity: a
response to strength training: changes in muscle architecture. J
comparison of dynamic and isometric measures of strength and
Physiol 2001; 534: 613-23
speed-strength. Eur J Appl Physiol 1994; 68: 350-5
45. Ahtiainen JP, Pakarinen A, Alen M, et al. Muscle hypertrophy,
27. Tesch PA, Ekberg A, Lindquist DM, et al. Muscle hypertrophy
hormonal adaptations and strength development during
following 5-week resistance training using a non-gravity-de-
strength training in strength-trained and untrained men. Eur J
pendent exercise system. Acta Physiol Scand 2004; 180: 89-98
Appl Physiol 2003; 89: 555-63
28. Caruso JF, Hamill JL, Hernandez DA, et al. A comparison of
46. Ahtiainen JP, Pakarinen A, Alen M, et al. Short vs long rest
isoload and isoinertial leg press training on bone and muscle
period between the sets in hypertrophic resistance training:
outcomes. J Strength Cond Res 2005; 19: 592-8
influence on muscle strength, size, and hormonal adaptations
29. Murphy AJ, Wilson GJ. The assessment of human dynamic
in trained men. J Strength Cond Res 2005; 19: 572-82
muscular function: a comparison of isoinertial and isokinetic
47. D’Antona G, Lanfranconi F, Pellegrino MA, et al. Skeletal
tests. J Sports Med Phys Fitness 1996; 36: 169-77
muscle hypertrophy and structure and function of skeletal
30. Hoeger WWK, Hopkins DR, Barette SL, et al. Relationship
muscle fibres in male body builders. J Physiol 2006; 570:
between repetitions and selected percentages of one repetition
611-27
maximum: a comparison between untrained and trained males
48. Housh DJ, Housh TJ, Johnson GO, et al. Hypertrophic response
and females. J Appl Sports Sci Res 1990; 4: 47-54
to unilateral concentric isokinetic resistance training. J Appl
31. Hickson RC, Hidaka K, Foster C. Skeletal muscle fiber type,
Physiol 1992; 73: 65-70
resistance training, and strength-related performance. Med Sci
49. Tracy BL, Ivey FM, Hurlbut D, et al. Muscle quality: II. Effects
Sports Exerc 1994; 26: 593-8
of strength training in 65- to 75-yr-old men and women. J Appl
32. Wathan D. Load assignment. In: Baechle T, editor. Essentials of
Physiol 1999; 86: 195-201
strength training and conditioning. Champaign (IL): Human
50. Aagaard P, Simonsen EB, Andersen JL, et al. MRI assessment
Kinetics, 1994: 435-9
of quadriceps muscle size before and after resistance training:
33. LaSuer DA, McCormick JH, Mayhew JL, et al. The accuracy of
determination of volume vs single-site CSA. Med Sci Sports
prediction equations for estimating 1-RM performance in the
Exerc 2001; 33 (5 Suppl.): S147
bench press, squat, and deadlift. J Strength Cond Res 1997; 11:
211-3
51. Tracy BL, Ivey FM, Metter EJ, et al. Muscle volume measure-
ment: single vs multiple axial MRI slices. Med Sci Sports
34. Dudley GA, Harris RT, Duvoisin MR. Effect of voluntary vs
Exerc 1999; 31 (5 Suppl.): S384
artificial activation on the relationship of muscle torque to
speed. J Appl Physiol 1990; 69: 2215-21
52. Tracy BL, Ivey FM, Metter EJ, et al. A more efficient magnetic
35. Amiridis IG, Martin A, Morlon B, et al. Co-activation and resonance imaging-based strategy for measuring quadriceps
tension-regulating phenomena during isokinetic knee exten- muscle volume. Med Sci Sports Exerc 2003; 35: 425-33
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
260 Wernbom et al.
53. McCall GE, Byrnes WC, Dickinson A, et al. Muscle fiber 71. H
¨
akkinen K, Kallinen M, Izquierdo M, et al. Changes in ago-
hypertrophy, hyperplasia, and capillary density in college men nist-antagonist EMG, muscle CSA, and force during strength
after resistance training. J Appl Physiol 1996; 81: 2004-12 training in middle-aged and older people. J Appl Physiol 1998;
84: 1341-9
54. Young A, Stokes M, Round JM, et al. The effect of high-
72. Ivey FM, Roth SM, Ferrell RE, et al. Effects of age, gender, and
resistance training on the strength and cross-sectional area of
myostatin genotype on the hypertrophic response to heavy
the human quadriceps. Eur J Clin Invest 1983; 13: 411-7
resistance strength training. J Gerontol A Biol Sci Med Sci
55. Jones DA, Rutherford OM. Human muscle strength training: the
2000; 55: M641-8
effects of three different regimes and the nature of the resultant
73. Izquierdo M, H
¨
akkinen K, Ibanez J, et al. Effects of strength
changes. J Physiol 1987; 391: 1-11
training on muscle power and serum hormones in middle-aged
56. H
¨
akkinen K, Kallinen M, Komi PV, et al. Neuromuscular
and older men. J Appl Physiol 2001; 90: 1497-507
adaptations during short-term ‘normal’ and reduced training
74. H
¨
akkinen K, Pakarinen A, Hannonen P, et al. Effects of strength
periods in strength athletes. Electromyogr Clin Neurophysiol
training on muscle strength, cross-sectional area, maximal
1991; 31: 35-42
electromyographic activity, and serum hormones in preme-
57. Rutherford OM, Jones DA. Measurement of fibre pennation
nopausal women with fibromyalgia. J Rheumatol 2002; 29:
using ultrasound in the human quadriceps in vivo. Eur J Appl
1287-95
Physiol 1992; 65: 433-7
75. Takarada Y, Ishii N. Effects of low-intensity resistance exercise
58. Sale DG, Martin JE, Moroz DE. Hypertrophy without increased
with short interset rest period on muscular function in middle-
isometric strength after weight training. Eur J Appl Physiol
aged women. J Strength Cond Res 2002; 16: 123-8
1992; 64: 51-5
76. Takarada Y, Sato Y, Ishii N. Effects of resistance exercise
59. H
¨
akkinen K, Pakarinen A, Kallinen M. Neuromuscular adapta-
combined with vascular occlusion on muscle function in ath-
tions and serum hormones in women during short-term inten-
letes. Eur J Appl Physiol 2002; 86: 308-14
sive strength training. Eur J Appl Physiol 1992; 64: 106-11
77. McCarthy JP, Pozniak MA, Agre JC. Neuromuscular adapta-
60. Ploutz LL, Tesch PA, Biro RL, et al. Effect of resistance training
tions to concurrent strength and endurance training. Med Sci
on muscle use during exercise. J Appl Physiol 1994; 76:
Sports Exerc 2002; 34: 511-9
1675-81
78. H
¨
akkinen K, Alen M, Kraemer WJ, et al. Neuromuscular adap-
61. H
¨
akkinen K, Kallinen M. Distribution of strength training vol-
tations during concurrent strength and endurance training ver-
ume into one or two daily sessions and neuromuscular adapta-
sus strength training. Eur J Appl Physiol 2003; 89: 42-52
tions in female athletes. Electromyogr Clin Neurophysiol
79. Vikne H, Refsnes PE, Medbø JI. Effect of training frequency of
1994; 34: 117-24
maximum eccentric strength training on muscle force and
62. Smith RC, Rutherford OM. The role of metabolites in strength
cross-sectional area in strength-trained athletes [abstract no.
training: part I. A comparison of eccentric and concentric
RR-PL-0517]. In: Book of abstracts, 14th International WCPT
contractions. Eur J Appl Physiol 1995; 71: 332-6
Congress; 2003 June 7-12; Barcelona
63. H
¨
akkinen K, H
¨
akkinen A. Neuromuscular adaptations during
80. Friedmann B, Kinscherf R, Borisch S, et al. Effects of low-
intensive strength training in middle-aged and elderly males
resistance/high-repetition strength training in hypoxia on mus-
and females. Electromyogr Clin Neurophysiol 1995; 35:
cle structure and gene expression. Pflugers Arch 2003; 446:
137-47
742-51
64. H
¨
akkinen K, Kallinen M, Linnamo V, et al. Neuromuscular
81. Friedmann B, Kinscherf R, Vorwald S, et al. Muscular adapta-
adaptations during bilateral versus unilateral strength training
tions to computer-guided strength training with eccentric over-
in middle-aged and elderly men and women. Acta Physiol
load. Acta Physiol Scand 2004; 182: 77-88
Scand 1996; 158: 77-88
82. Goto K, Nagasawa M, Yanagisawa O, et al. Muscular adapta-
65. Hisaeda H, Miyagawa K, Kuno S, et al. Influence of two
tions to combinations of high- and low-intensity resistance
different modes of resistance training in female subjects. Ergo-
exercises. J Strength Cond Res 2004; 18: 730-7
nomics 1996; 39: 842-52
83. Takarada Y, Tsuruta T, Ishii N. Cooperative effects of exercise
66. Welle S, Totterman S, Thornton C. Effect of age on muscle
and occlusive stimuli on muscular function in low-intensity
hypertrophy induced by resistance training. J Gerontol A Biol
resistance exercise with moderate vascular occlusion. Jpn J
Sci Med Sci 1996; 51: M270-5
Physiol 2004; 54: 585-92
67. McCarthy JP, Bamman MM, Yelle JM, et al. Resistance exer-
84. Abe T, Yasuda T, Midorikawa T, et al. Skeletal muscle size and
cise training and the orthostatic response. Eur J Appl Physiol
circulating IGF-1 are increased after two weeks of twice daily
1997; 76: 32-40
Kaatsu resistance training [online]. Int J Kaatsu Training Res
2005; 1: 7-14. Available from URL: http://kaatsu.jp/english/
68. Housh DJ, Housh TJ, Weir JP, et al. Effects of unilateral
j01_1.html [Accessed 2005 April 25]
concentric-only dynamic constant external resistance training
on quadriceps femoris cross-sectional area. J Strength Cond
85. Goto K, Ishii N, Kizuka T, et al. The impact of metabolic stress
Res 1998; 12: 185-91
on hormonal responses and muscular adaptations. Med Sci
Sports Exerc 2005; 37: 955-63
69. Housh DJ, Housh TJ, Weir JP, et al. Effects of unilateral
eccentric-only dynamic constant external resistance training
86. Izquierdo M, H
¨
akkinen K, Ibanez J, et al. Effects of combined
on quadriceps femoris cross-sectional area. J Strength Cond
resistance and cardiovascular training on strength, power,
Res 1998; 12: 192-8
muscle cross-sectional area, and endurance markers in middle-
aged men. Eur J Appl Physiol 2005; 94: 70-5
70. H
¨
akkinen K, Newton RU, Gordon SE, et al. Changes in muscle
morphology, electromyographic activity, and force production 87. Norrbrand L, Pozzo M, Tesch P. J
¨
amf
¨
orelse av tr
¨
aningseffekter
characteristics during progressive strength training in young efter 5 veckors styrketr
¨
aning med tv
˚
a olika belastningsst-
and older men. J Gerontol A Biol Sci Med Sci 1998; 53: rategier (in Swedish) [abstract]. Svensk Idrottsmedicin 2005;
B415-23 24 (4): 30-1
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
Strength Training and Muscle Cross-Sectional Area 261
88. Tanimoto M, Ishii N. Effects of low-intensity resistance exer- 107. Schott J, McCully K, Rutherford OM. The role of metabolites in
cise with slow movement and tonic force generation on muscu- strength training: II. Short versus long isometric contractions.
lar function in young men. J Appl Physiol 2006; 100: 1150-7 Eur J Appl Physiol 1995; 71: 337-41
108. Kubo K, Kanehisa H, Fukunaga T. Effects of different duration
89. Coburn JW, Housh DJ, Housh TJ, et al. Effects of leucine and
isometric contractions on tendon elasticity in human quadri-
whey protein supplementation during 8 weeks of unilateral
ceps muscles. J Physiol 2000; 536: 649-55
resistance training. J Strength Cond Res 2006; 20: 284-9
109. Kubo K, Ohgo K, Takeishi R, et al. Effects of isometric training
90. Kubo K, Komuro T, Ishiguro N, et al. Effects of low-load
at different knee angles on the muscle-tendon complex in vivo.
resistance training with vascular occlusion on the mechanical
Scand J Med Sci Sports 2006; 16: 159-67
properties of muscle and tendon. J Appl Biomech. 2006; 22:
112-9
110. Kubo K, Yata H, Kanehisa H, et al. Effects of isometric squat
training on the tendon stiffness and jump performance. Eur J
91. Leger B, Cartoni R, Praz M, et al. Akt signalling through
Appl Physiol 2006; 96: 305-14
GSK-3{beta}, mTOR and foxo1 is involved in human skeletal
muscle hypertrophy and atrophy. J Physiol 2006; 576: 923-33
111. Sale DG, MacDougall JD, Jacobs I, et al. Interaction between
concurrent strength and endurance training. J Appl Physiol
92. Popov DV, Swirkun DV, Netreba AI, et al. Hormonal adapta-
1990; 68: 260-70
tion determines the increase in muscle mass and strength
during low-intensity strength training without relaxation.
112. Sale DG, Jacobs I, MacDougall JD, et al. Comparison of two
Human Physiology 2006; 32 (5): 609-14
regimens of concurrent strength and endurance training. Med
Sci Sports Exerc 1990; 22: 348-56
93. Petersen SR, Bagnall KM, Wenger HA, et al. The influence of
velocity-specific resistance training on the in vivo torque-
113. Kraemer WJ, Nindl BC, Ratamess NA, et al. Changes in muscle
velocity relationship and the cross-sectional area of quadriceps
hypertrophy in women with periodized resistance training.
femoris. J Orthop Sports Phys Ther 1989; 11: 456-62
Med Sci Sports Exerc 2004; 36: 697-708
94. Petersen S, Wessel J, Bagnall K, et al. Influence of concentric
114. Akima H, Kubo K, Kanehisa H, et al. Leg-press resistance
resistance training on concentric and eccentric strength. Arch
training during 20 days of 6 degrees head-down-tilt bed rest
Phys Med Rehabil 1990; 71: 101-5
prevents muscle deconditioning. Eur J Appl Physiol 2000; 82:
30-8
95. Petersen SR, Bell GJ, Bagnall KM, et al. Influence of concentric
resistance training on eccentric peak torque and muscle cross-
115. Akima H, Kubo K, Imai M, et al. Inactivity and muscle: effect of
sectional area. J Orthop Sports Phys Ther 1991; 13: 132-7
resistance training during bed rest on muscle size in the lower
limb. Acta Physiol Scand 2001; 172: 269-78
96. Bell GJ, Petersen SR, Wessel J, et al. Physiological adaptations
to concurrent endurance training and low velocity resistance
116. Schulze K, Gallagher P, Trappe S. Resistance training preserves
training. Int J Sports Med 1991; 12: 384-90
skeletal muscle function during unloading in humans. Med Sci
Sports Exerc 2002; 34: 303-13
97. Bell GJ, Petersen SR, Wessel J, et al. Adaptations to endurance
training and low velocity resistance training performed in a
117. Kubo K, Akima H, Ushiyama J, et al. Effects of resistance
sequence. Can J Sport Sci 1991; 16: 186-92
training during bed rest on the viscoelastic properties of tendon
structures in the lower limb. Scand J Med Sci Sports 2004; 14:
98. Bell GJ, Petersen SR, MacLean I, et al. Effect of high velocity
296-302
resistance training on peak torque, cross sectional area and
myofibrillar ATPase activity. J Sports Med Phys Fitness 1992;
118. Tesch PA, Trieschmann JT, Ekberg A. Hypertrophy of chroni-
32: 10-8
cally unloaded muscle subjected to resistance exercise. J Appl
Physiol 2004; 96: 1451-8
99. Ruther CL, Golden CL, Harris RT, et al. Hypertrophy, resis-
tance training, and the nature of skeletal muscle activation. J
119. Alkner BA, Tesch PA. Efficacy of a gravity-independent resis-
Strength Cond Res 1995; 9: 155-9
tance exercise device as a countermeasure to muscle atrophy
during 29-day bed rest. Acta Physiol Scand 2004; 181: 345-57
100. Higbie EJ, Cureton KJ, Warren GL, et al. Effects of concentric
and eccentric training on muscle strength, cross-sectional area,
120. Shackelford LC, LeBlanc AD, Driscoll TB. Resistance exercise
and neural activation. J Appl Physiol 1996, 81
as a countermeasure to disuse-induced bone loss. J Appl Physi-
ol 2004; 97: 119-29
101. Housh DJ, Housh TJ, Weir JP, et al. Concentric isokinetic
resistance training and quadriceps femoris cross-sectional
121. Mulder ER, Stegeman DF, Gerrits KH, et al. Strength, size and
area. Isokin Exerc Sci 1996; 6: 101-8
activation of knee extensors followed during 8 weeks of hori-
zontal bed rest and the influence of a countermeasure. Eur J
102. Seger JY, Arvidsson B, Thorstensson A. Specific effects of
Appl Physiol. 2006; 97: 706-15
eccentric and concentric training on muscle strength and mor-
phology in humans. Eur J Appl Physiol 1998; 79: 49-57
122. Stevenson SW, Dudley GA. Dietary creatine supplementation
and muscular adaptation to resistive overload. Med Sci Sports
103. Akima H, Takahashi H, Kuno SY, et al. Early phase adaptations
Exerc 2001; 33: 1304-10
of muscle use and strength to isokinetic training. Med Sci
Sports Exerc 1999; 31: 588-94
123. Gondin J, Guette M, Ballay Y, et al. Electromyostimulation
training effects on neural drive and muscle architecture. Med
104. Rafeei T. The effects of training at equal power levels using
Sci Sports Exerc 2005; 37: 1291-9
concentric and eccentric contractions on skeletal muscle fiber
and whole muscle hypertrophy, muscle force and muscle acti-
124. Fukunaga T, Sugiyama M. The effect of static and dynamic
vation in human subjects [dissertation]. Richmond (VA): Vir-
strength training on absolute muscle strength. Jap J Phys Educ
ginia Commonwealth University, 1999
1978; 22: 343-9
105. Seynnes OR, de Boer M, Narici MV. Early skeletal muscle
125. Sale D, MacDougall D, Alway S, et al. Effect of low vs high
hypertrophy and architectural changes in response to high-
repetition weight training upon strength, muscle size and mus-
intensity resistance training. J Appl Physiol. Epub 2006 Oct 19
cle fiber size [abstract]. Can J Spt Sci 1985; 10 (4): 27P
106. Garfinkel S, Cafarelli E. Relative changes in maximal force, 126. Refsnes PE. En treningsmetode, hvor en aktivert muskel strek-
EMG, and muscle cross-sectional area after isometric training. kes forut for forkortning, og denne treningsmetodens innvirkn-
Med Sci Sports Exerc 1992; 24: 1220-7 ing p
˚
a 1RM og vinkelhastighet ved lett belastning (in Norwe-
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
262 Wernbom et al.
gian) [dissertation]. Norwegian School of Sport Sciences, Os- 144. Garhammer J, Takano B. Training for weightlifting. In: Komi
lo, Norway, 1986 PV, editor. Strength and power in sport. Oxford: Blackwell
scientific publications, 1992: 357-69
127. Dahl HA, Aaserud R, Jensen J. Muscle hypertrophy after light
145. Tesch PA. Strength training and muscle hypertrophy. In: H
¨
ak-
and heavy resistance training [abstract]. Med Sci Sports Exerc
kinen K, editor. Conference book: international conference on
1992; 24 (5 Suppl.): S55
weightlifting and strength training; Lahti, Finland, 1998 No-
128. Narici MV, Kayser B. Hypertrophic response of human skeletal
vember 10-12; Jyv
¨
askyl
¨
a: Gummerus printing, 1998: 17-22
muscle to strength training in hypoxia and normoxia. Eur J
146. Ostrowski K, Wilson GJ, Weatherby R, et al. The effect of
Appl Physiol 1995; 70: 213-9
weight training volume on hormonal output and muscular size
129. Moss BM, Refsnes PE, Abildgaard A, et al. Effects of maximal
and function. J Strength Cond Res 1997; 11: 148-54
effort strength training with different loads on dynamic
147. McLester JR, Bishop P, Guilliams ME. Comparison of 1 day
strength, cross-sectional area, load-power and load-velocity
and 3 days per week of equal-volume resistance training in
relationships. Eur J Appl Physiol 1997; 75: 193-9
experienced subjects. J Strength Cond Res 2000; 14: 273-81
130. Bemben DA, Fetters NL, Bemben MG, et al. Musculoskeletal
148. Hawkins SA, Schroeder ET, Wiswell RA, et al. Eccentric mus-
responses to high- and low-intensity resistance training in early
cle action increases site-specific osteogenic response. Med Sci
postmenopausal women. Med Sci Sports Exerc 2000; 32:
Sports Exerc 1999; 31: 1287-92
1949-57
149. Hortobagyi T, Hill JP, Houmard JA, et al. Adaptive responses to
131. Takarada Y, Takazawa H, Sato Y, et al. Effects of resistance
muscle lengthening and shortening in humans. J Appl Physiol
exercise combined with moderate vascular occlusion on mus-
1996; 80: 765-72
cular function in humans. J Appl Physiol 2000; 88: 2097-106
150. Hortobagyi T, Dempsey L, Fraser D, et al. Changes in muscle
132. Okada J, Fukashiro S. Effects of resistance training associated
strength, muscle fibre size and myofibrillar gene expression
with stretch-shortening cycle exercise on force development
after immobilization and retraining in humans. J Physiol 2000;
and muscle volume in human elbow flexors. Adv Exerc Sports
524: 293-304
Physiol 2001; 7: 65-71
151. Farthing JP, Chilibeck PD. The effects of eccentric and concen-
133. Brandenburg JP, Docherty D. The effects of accentuated eccen-
tric training at different velocities on muscle hypertrophy. Eur
tric loading on strength, muscle hypertrophy and neural adap-
J Appl Physiol 2003; 89: 578-86
tations in trained individuals. J Strength Cond Res 2002; 16:
152. Ewing JL, Wolfe DR, Rogers MA, et al. Effects of velocity of
25-32
isokinetic training on strength, power, and quadriceps muscle
134. Wirth K, Atzor KR, Schmidtbleicher D. Changes in muscle fibre characteristics. Eur J Appl Physiol 1990; 61: 159-62
mass detected by MRI, after an eight week hypertrophy train-
153. Coyle EF, Feiring DC, Rotkis TC, et al. Specificity of power
ing program. In: Koskolou M, editor. Proceedings of 7th
improvements through slow and fast isokinetic training. J Appl
annual Congress of the European College of Sports Sciences;
Physiol 1981; 51: 1437-42
2002 Jul 24-27; Athens, 103
154. Aagaard P, Simonsen EB, Trolle M, et al. Moment and power
generation during maximal knee extensions performed at low
135. Walker KS, Kambadur R, Sharma M, et al. Resistance training
and high speeds. Eur J Appl Physiol 1994; 69: 376-81
alters plasma myostatin but not IGF-1 in healthy men. Med Sci
Sports Exerc 2004; 36: 787-93
155. Thome
´
e R, Renstr
¨
om P, Grimby G, et al. Slow or fast isokinetic
training after knee ligament surgery. J Orthop Sports Phys
136. Hubal MJ, Gordish-Dressman H, Thompson PD, et al. Variabili-
Ther 1987; 8: 475-9
ty in muscle size and strength gain after unilateral resistance
156. Frob
¨
ose I, Verdonck A, Duesberg F, et al. Effects of various
training. Med Sci Sports Exerc 2005; 37: 964-72
load intensities in the framework of postoperative stationary
137. Vikne H, Refsnes PE, Ekmark M, et al. Muscular performance
endurance training on performance deficit of the quadriceps
after concentric and eccentric exercise in trained men. Med Sci
muscle of the thigh [in German]. Z Orthop Ihre Grenzgeb
Sports Exerc 2006; 38: 1770-81
1993; 131: 164-7
138. Shepstone TN, Tang JE, Dallaire S, et al. Short-term high- vs
157. Greenhaff PL, Soderlund K, Ren JM, et al. Energy metabolism
low-velocity isokinetic lengthening training results in greater
in single human muscle fibres during intermittent contraction
hypertrophy of the elbow flexors in young men. J Appl Physiol
with occluded circulation. J Physiol 1993; 460: 443-53
2005; 98: 1768-76
158. McHugh MP, Tyler TF, Greenberg SC, et al. Differences in
139. Davies J, Parker DF, Rutherford OM, et al. Changes in strength
activation patterns between eccentric and concentric quadri-
and cross-sectional area of the elbow flexors as a result of
ceps contractions. J Sports Sci 2002; 20: 83-91
isometric strength training. Eur J Appl Physiol 1988; 57:
159. Starkey DB, Pollock ML, Ishida Y, et al. Effect of resistance
667-70
training volume on strength and muscle thickness. Med Sci
140. Chesley A, MacDougall JD, Tarnopolsky MA, et al. Changes in
Sports Exerc 1996; 28: 1311-20
human muscle protein synthesis after resistance exercise. J
160. Pollock ML, Abe T, DeHoyos DV, et al. Muscular hypertrophy
Appl Physiol 1992; 73: 1383-8
responses to 6 months of high or low volume resistance
141. MacDougall JD, Gibala MJ, Tarnopolsky MA, et al. The time
training [abstract]. Med Sci Sports Exerc 1998; 30 (5 Suppl.):
course for elevated muscle protein synthesis following heavy
S116
resistance exercise. Can J Appl Physiol 1995; 20: 480-6
161. McBride JM, Blaak JB, Triplett-McBride T. Effect of resistance
142. Phillips SM, Tipton KD, Aarsland A, et al. Mixed muscle
exercise volume and complexity on EMG, strength, and re-
protein synthesis and breakdown after resistance exercise in
gional body composition. Eur J Appl Physiol 2003; 90: 626-32
humans. Am J Physiol 1997; 273: E99-107
162. Ronnestad RB, Kadi F, Raastad T, et al. Dissimilar effects of 1
143. Miller BF, Olesen JL, Hansen M, et al. Coordinated collagen and 3 set strength training on strength and muscle mass gains
and muscle protein synthesis in human patella tendon and in upper and lower body in untrained subjects. J Strength Cond
quadriceps muscle after exercise. J Physiol 2005; 567: 1021-33 Res. In press
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
Strength Training and Muscle Cross-Sectional Area 263
163. Mayhew TP, Rothstein JM, Finucane SD, et al. Muscular adap- 181. Kawakami Y, Abe T, Kuno SY, et al. Training-induced changes
tation to concentric and eccentric exercise at equal power in muscle architecture and specific tension. Eur J Appl Physiol
levels. Med Sci Sports Exerc 1995; 27: 868-73 1995; 72: 37-43
182. Amiridis IG, Cometti G, Morlon B, et al. Effects of the type of
164. Herzog W, Abrahamse SK, ter Keurs HE. Theoretical determi-
recovery training on the concentric strength of the knee exten-
nation of force-length relations of intact human skeletal mus-
sors. J Sports Sci 1997; 15: 175-80
cles using the cross-bridge model. Pflugers Arch 1990; 416:
113-9
183. LaStayo PC, Pierotti DJ, Pifer J, et al. Eccentric ergometry:
increases in locomotor muscle size and strength at low training
165. Ichinose Y, Kawakami Y, Ito M, et al. Estimation of active
intensities. Am J Physiol Regul Integr Comp Physiol 2000;
force-length characteristics of human vastus lateralis muscle.
278: R1282-8
Acta Anat (Basel) 1997; 159: 78-83
184. LaStayo PC, Ewy GA, Pierotti DD, et al. The positive effects of
166. Westing SH, Seger JY, Thorstensson A. Effects of electrical
negative work: increased muscle strength and decreased fall
stimulation on eccentric and concentric torque-velocity rela-
risk in a frail elderly population. J Gerontol A Biol Sci Med Sci
tionships during knee extension in man. Acta Physiol Scand
2003; 58: M419-24
1990; 140: 17-22
185. Gerber JP, Marcus RL, Dibble LE, et al. Early application of
167. Dugailly PM, Mouraux D, Llamas N, et al. EMGs and strength
negative work via eccentric ergometry following anterior cru-
patterns of the quadriceps during isokinetic extension of the
ciate ligament reconstruction: a case report. J Orthop Sports
knee in different contraction mode. Isokin Exerc Sci 2002; 10:
Phys Ther 2006; 36: 298-307
21-2
186. Fry AC. The role of training intensity in resistance exercise
168. Holder-Powell HM, Rutherford OM. Reduction in range of
overtraining and overreaching. In: Kreider RB, Fry AC,
movement can increase maximum voluntary eccentric forces
O’Toole ML, editors. Overtraining in sport. Champaign (IL):
for the human knee extensor muscles. Eur J Appl Physiol
Human Kinetics, 1998: 107-27
1999; 80: 502-4
187. Peterson MD, Rhea MR, Alvar BA. Applications of the dose-
169. Colliander E. Influence of concentric and eccentric muscle
response for muscular strength development: a review of meta-
actions on acute strength patterns and adaptive responses to
analytic efficacy and reliability for designing training prescrip-
resistance training [dissertation]. Stockholm: Karolinska Insti-
tion. J Strength Cond Res 2005; 19: 950-8
tutet, 1992
188. Refsnes PE. Testing and training for top Norwegian athletes. In:
170. Ichinose Y, Kawakami Y, Ito M, et al. In vivo estimation of
M
¨
uller E, Zallinger G, Ludescher F, editors. Science in elite
contraction velocity of human vastus lateralis muscle during
sport. London: E & FN Spon, 1999: 97-114
‘isokinetic’ action. J Appl Physiol 2000; 88: 851-6
189. American College of Sports Medicine Position Stand. The rec-
171. Rooney KJ, Herbert RD, Balnave RJ. Fatigue contributes to the
ommended quantity and quality of exercise for developing and
strength training stimulus. Med Sci Sports Exerc 1994; 26:
maintaining cardiorespiratory and muscular fitness, and flexi-
1160-4
bility in healthy adults. Med Sci Sports Exerc 1998; 30: 975-91
172. Drinkwater EJ, Lawton TW, Lindsell RP, et al. Training leading
190. Wallace MB, Mills BD, Browning CL. Effects of cross-training
to repetition failure enhances bench press strength gains in
on markers of insulin resistance/hyperinsulinemia. Med Sci
elite junior athletes. J Strength Cond Res 2005; 19: 382-8
Sports Exerc 1997; 29: 1170-5
173. Pincivero DM, Campy RM. The effects of rest interval length
191. Woods RH, Reyes R, Welsch MA, et al. Concurrent cardiovas-
and training on quadriceps femoris muscle: part I. Knee exten-
cular and resistance training in healthy older adults. Med Sci
sor torque and muscle fatigue. J Sports Med Phys Fitness 2004;
Sports Exerc 2001; 33: 1751-8
44: 111-8
192. Kraemer WJ, Keuning M, Ratamess NA, et al. Resistance
174. Folland JP, Irish CS, Roberts JC, et al. Fatigue is not a necessary
training combined with bench-step aerobics enhances
stimulus for strength gains during resistance training. Br J
women’s health profile. Med Sci Sports Exerc 2001; 33:
Sports Med 2002; 36: 370-3
259-69
175. Tesch PA, Dudley GA, Duvoisin MR, et al. Force and EMG
193. Kawano H, Tanaka H, Miyachi M. Resistance training and
signal patterns during repeated bouts of concentric or eccentric
arterial compliance: keeping the benefits while minimizing the
muscle actions. Acta Physiol Scand 1990; 138: 263-71
stiffening. J Hypertens 2006; 24: 1753-9
176. Grabiner MD, Owings TM. Effects of eccentrically and concen-
194. Leveritt M, Abernethy PJ, Barry BK, et al. Concurrent strength
trically induced unilateral fatigue on the involved and
and endurance training: a review. Sports Med 1999; 28: 413-27
uninvolved limbs. J Electromyogr Kinesiol 1999; 9: 185-9
195. Deakin GB. Concurrent training in endurance athletes: the acute
177. Kay D, St Clair Gibson A, Mitchell MJ, et al. Different neuro-
effects on muscle recovery capacity, physiological, hormonal
muscular recruitment patterns during eccentric, concentric and
and gene expression responses post-exercise (dissertation) [on-
isometric contractions. J Electromyogr Kinesiol 2000; 10:
line]. Lismore, Australia: Southern Cross University, 2004.
425-31
Available from URL: http://thesis.scu.edu.au/ [Accessed 2006
178. Dow DE, Cederna PS, Hassett CA, et al. Number of contrac-
Dec 3]
tions to maintain mass and force of a denervated rat muscle.
196. Staron RS, Karapondo DL, Kraemer WJ, et al. Skeletal muscle
Muscle Nerve 2004; 30: 77-86
adaptations during early phase of heavy-resistance training in
men and women. J Appl Physiol 1994; 76: 1247-55
179. Dow DE, Faulkner JA, Dennis RG. Distribution of rest periods
between electrically generated contractions in denervated mus-
197. Sale DG. Neural adaptations to strength training. In: Komi PV,
cles of rats. Artif Organs 2005; 29: 432-5
editor. Strength and power in sport. 2nd ed. Oxford: Blackwell
scientific publications, 2003: 281-314
180. Dow DE, Dennis RG, Faulkner JA. Electrical stimulation atten-
uates denervation and age-related atrophy in extensor dig- 198. Phillips SM. Short-term training: when do repeated bouts of
itorum longus muscles of old rats. J Gerontol A Biol Sci Med resistance exercise become training? Can J Appl Physiol 2000;
Sci 2005; 60: 416-24 25: 185-93
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
This material is
the copyright of the
original publisher.
Unauthorised copying
and distribution
is prohibited.
264 Wernbom et al.
199. Willoughby DS, Taylor L. Effects of sequential bouts of resis- 216. Martineau LC, Gardiner PF. Insight into skeletal muscle mecha-
tance exercise on androgen receptor expression. Med Sci
notransduction: MAPK activation is quantitatively related to
Sports Exerc 2004; 36: 1499-506
tension. J Appl Physiol 2001; 91: 693-702
200. Foley JM, Jayaraman RC, Prior BM, et al. MR measurements of
217. Martineau LC, Gardiner PF. Skeletal muscle is sensitive to the
muscle damage and adaptation after eccentric exercise. J Appl
tension-time integral but not to the rate of change of tension, as
Physiol 1999; 87: 2311-8
assessed by mechanically induced signaling. J Biomech 2002;
201. Willoughby DS, Taylor M, Taylor L. Glucocorticoid receptor
35: 657-63
and ubiquitin expression after repeated eccentric exercise. Med
218. Eliasson J, Elfegoun T, Nilsson J, et al. Maximal lengthening
Sci Sports Exerc 2003; 35: 2023-31
contractions increase p70S6 kinase phosphorylation in human
202. Trappe TA, Raue U, Tesch PA. Human soleus muscle protein
skeletal muscle in the absence of nutritional supply. Am J
synthesis following resistance exercise. Acta Physiol Scand
Physiol Endocrinol Metab 2006; 291: E1197-205
2004; 182: 189-96
219. Cuthbertson DJ, Babraj J, Smith K, et al. Anabolic signaling and
203. Turner DL, Hoppeler H, Claassen H, et al. Effects of endurance
protein synthesis in human skeletal muscle after dynamic
training on oxidative capacity and structural composition of
shortening or lengthening exercise. Am J Physiol Endocrinol
human arm and leg muscles. Acta Physiol Scand 1997; 161:
Metab 2006; 290: 731-8
459-64
220. Jones DA, Folland JP. Strength training in young adults. In:
204. Abe T, DeHoyos DV, Pollock ML, et al. Time course for
Maffuli N, Chan KM, Macdonald R, et al., editors. Sports
strength and muscle thickness changes following upper and
medicine for specific ages abilities. Edinburgh: Churchill Liv-
lower body resistance training in men and women. Eur J Appl
ingstone, 2001: 57-64
Physiol 2000; 81: 174-80
221. Kraemer WJ, Ratamess NA. Hormonal responses and adapta-
205. Rennie MJ, Wackerhage H, Spangenburg EE, et al. Control of
tions to resistance exercise and training. Sports Med 2005; 35:
the size of the human muscle mass. Annu Rev Physiol 2004;
66: 799-828
339-61
222. Uehara K, Goto K, Kobayashi T, et al. Heat-stress enhances
206. Glass DJ. Skeletal muscle hypertrophy and atrophy signaling
pathways. Int J Biochem Cell Biol 2005; 37: 1974-84
proliferative potential in rat soleus muscle. Jpn J Physiol 2004;
54: 263-71
207. Nader GA. Molecular determinants of skeletal muscle mass:
getting the ‘AKT’ together. Int J Biochem Cell Biol 2005; 37:
223. Goto K, Okuyama R, Sugiyama H, et al. Effects of heat stress
1985-96
and mechanical stretch on protein expression in cultured skele-
tal muscle cells. Pflugers Arch 2003; 447: 247-53
208. Hornberger TA, Esser KA. Mechanotransduction and the regu-
lation of protein synthesis in skeletal muscle. Proc Nutr Soc
224. Goto K, Honda M, Kobayashi T, et al. Heat stress facilitates the
2004; 63: 331-5
recovery of atrophied soleus muscle in rat. Jpn J Physiol 2004;
54: 285-93
209. Hameed M, Orell RW, Cobbold M, et al. Expression of IGF-I
splice variants in young and old human skeletal muscle after
225. Abe T, Kawamoto K, Yasuda T, et al. Eight days Kaatsu-
high resistance exercise. J Physiol 2003; 547: 247-54
resistance training improved sprint but not jump performance
210. Hornberger TA, Chu WK, Mak YW, et al. The role of
in collegiate male track and field athletes [online]. Int J Kaatsu
phospholipase D and phosphatidic acid in the mechanical
Training Res 2005; 1: 19-23. Available from URL: http://
activation of mTOR signaling in skeletal muscle. Proc Natl
kaatsu.jp/english/j01_1.html. [Accessed 2005 April 25]
Acad Sci U S A 2006; 103: 4741-6
226. Mazzetti SA, Kraemer WJ, Volek JS, et al. The influence of
211. Boppart MD, Burkin DJ, Kaufman SJ. Alpha7beta1-integrin
direct supervision of resistance training on strength perform-
regulates mechanotransduction and prevents skeletal muscle
ance. Med Sci Sports Exerc 2000; 32: 1175-84
injury. Am J Physiol Cell Physiol 2006; 290: 1660-5
227. Mitsiopoulos N, Baumgartner RN, Heymsfield SB, et al. Cadav-
212. Spangenburg EE, McBride TA. Inhibition of stretch-activated
er validation of skeletal muscle measurement by magnetic
channels during eccentric muscle contraction attenuates
resonance imaging and computerized tomography. J Appl
p70S6K activation. J Appl Physiol 2006; 100: 129-35
Physiol 1998; 85: 115-22
213. Lange S, Xiang F, Yakovenko A, et al. The kinase domain of
titin controls muscle gene expression and protein turnover.
Science 2005; 308 (5728): 1599-603
Correspondence and offprints: Mathias Wernbom, Lundberg
214. Goldberg AL, Etlinger JD, Goldspink DF, et al. Mechanism of
Laboratory for Human Muscle Function and Movement
work-induced hypertrophy of skeletal muscle. Med Sci Sports
Analysis, Department of Orthopaedics, Sahlgrenska Uni-
1975; 7: 185-98
versity Hospital, Gr
¨
ona Str
˚
aket 12, G
¨
oteborg, SE-413 45,
215. MacDougall J. Adaptability of muscle to strength training: a
Sweden.
cellular approach. In: Saltin B, editor. Biochemistry of exer-
E-mail: mathias.wernbom@orthop.gu.se
cise VI. Champaign (IL): Human Kinetics, 1986: 501-13
2007 Adis Data Information BV. All rights reserved. Sports Med 2007; 37 (3)
... The interest in resistance training has risen in popularity (Wernbom, Augustsson & Thomee, 2007). Several studies pointed out that conducting resistance training had many potential health benefits for people of all ages (Winett & Carpinelli, 2001). ...
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Background In resistance training, the role of training frequency to increase maximal strength is often debated. However, the limited data available does not allow for clear training frequency “optimization” recommendations. The purpose of this study was to investigate the effects of training frequency on maximal muscular strength and rate of perceived exertion (RPE). The total weekly training volume was equally distributed between two and four sessions per muscle group. Methods Twenty-one experienced resistance-trained male subjects (height: 1.85 ± 0.06 m, body mass: 85.3 ± 12.3 kg, age: 27.6 ± 7.6 years) were tested prior to and after an 8-week training period in one-repetition maximum (1RM) barbell back squat and bench press. Subjects were randomly assigned to a SPLIT group ( n = 10), in which there were two training sessions of squats and lower-body exercises and two training sessions of bench press and upper-body exercises, or a FULLBODY group ( n = 11), in which four sessions with squats, bench press and supplementary exercises were conducted every session. In each session, the subjects rated their RPE after barbell back squat, bench press, and the full session. Results Both groups significantly increased 1RM strength in barbell back squat (SPLIT group: +13.25 kg; FULLBODY group: +14.31 kg) and bench press (SPLIT group: +7.75 kg; FULLBODY group: +8.86 kg) but training frequency did not affect this increase for squat ( p = 0.640) or bench press ( p = 0.431). Both groups showed a significant effect for time on RPE on all three measurements. The analyses showed only an interaction effect between groups on time for the RPE after the squat exercise ( p = 0.002). Conclusion We conclude that there are no additional benefits of increasing the training frequency from two to four sessions under volume-equated conditions, but it could be favorable to spread the total training volume into several training bouts through the week to avoid potential increases in RPE, especially after the squat exercise.
... Early evidence from longitudinal studies suggested that light-load training produced suboptimal skeletal muscle hypertrophy. A 2007 review of the literature by Wernbom et al. [44] concluded a hypertrophic benefit to training with loads >60% 1RM. However, the conclusion was based on a limited amount of data that directly compared the effects of training with varying loads on muscle hypertrophy at that point in time. ...
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Loading recommendations for resistance training are typically prescribed along what has come to be known as the “repetition continuum”, which proposes that the number of repetitions performed at a given magnitude of load will result in specific adaptations. Specifically, the theory postulates that heavy load training optimizes increases maximal strength, moderate load training optimizes increases muscle hypertrophy, and low-load training optimizes increases local muscular endurance. However, despite the widespread acceptance of this theory, current research fails to support some of its underlying presumptions. Based on the emerging evidence, we propose a new paradigm whereby muscular adaptations can be obtained, and in some cases optimized, across a wide spectrum of loading zones. The nuances and implications of this paradigm are discussed herein.
... In muscles, a reduction in muscle mass is a factor that increases the likelihood of injury and RT is an effective way of avoiding this [59]. Adaptations in the muscle occur at different stages, and at the beginning of the program there are rapid improvements in strength due to neuromuscular adaptations, followed by a slow progression as the muscle increases its cross-sectional area [60,61]. The neuromuscular adaptations observed are mainly: acquisition of a motor function by the nervous system, increased muscle activation and improved synchronization of motor units and improved intramuscular coordination [62]. ...
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Stand-up paddleboarding (SUP) is an increasingly popular sport but, as in other sports, there is an injury ratio associated with practicing it. In other types of sport, some factors have been linked to the likelihood of suffering an injury, among which stretching, core training and resistance training may be considered the most significant. Therefore, the main aim of this study was to identify the training factors that could influence injuries suffered by participants in international SUP competitions. Ninety-seven questionnaires were collected from paddlers who participated in an international SUP circuit, with epidemiological data being gathered about injuries and different questions related to the training undertaken. A multi-factor ANOVA test was used to identify the factors which influence the state of injury. Results showed that almost 60% of injuries occurred in the arms or in the upper thoracic region, around 65% of which were in tendons or muscles and, in almost half of cases, were related to overuse. Likewise, the results showed that athletes with injury performed fewer resistance training sessions per week (p = 0.028), over fewer months per year (p = 0.001), more weekly training sessions (p = 0.004) and, lastly, a greater volume of weekly training (p = 0.003) than athletes without injury. Moreover, the most important training factors that reduce the likelihood of suffering an injury were taken into account-in. particular, resistance training alone (p = 0.011) or together with CORE training (p = 0.006) or stretching (p = 0.012), and the dominant side of paddling (p = 0.032). In conclusion, resistance training would seem to reduce the likelihood of injury among SUP practitioners, and such benefits could be obtained by resistance training alone or in combination with CORE training or stretching.
... As mentioned by other authors, the increase in muscle volume is not proportional to the duration of training. After three months of training, the increase in muscle volume becomes low or even non-existent [58]. More recently, a meta-analysis has been conducted to compare changes in strength and hypertrophy between low (≤60% of 1RM) vs. high-load (>60% of 1RM) resistance training protocols [59]. ...
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Background: To investigate how anatomical cross-sectional area and volume of quadriceps and triceps surae muscles were affected by ageing, and by resistance training in older and younger men, in vivo. Methods: The old participants were randomly assigned to moderate (O55, n=13) or high-load (O80, n=14) resistance training intervention (12 weeks; 3 times/week) corresponding to 55% or 80% of one repetition maximum, respectively. Young men (Y55, n=11) were assigned to the moderate-intensity strengthening exercise program. Each group received the exact same training volume on triceps surae and quadriceps group (Reps x Sets x Intensity). The fitting polynomial regression equations for each of anatomical cross-sectional area-muscle length curves were used to calculate muscle volume (contractile content) before and after 12 weeks using magnetic resonance imaging scans. Results: Only Rectus femoris and medial gastrocnemius muscle showed a higher relative anatomical cross-sectional area in the young than the elderly on the proximal end. The old group displayed a higher absolute volume of non-contractile material than young men in triceps surae (+96%). After training, Y55, O55 and O80 showed an increase in total quadriceps (+4.3%; +6.7%; 4.2% respectively) and triceps surae (+2.8%; +7.5%; 4.3% respectively) volume. O55 demonstrated a greater increase on average gains compared to Y55, while no difference between O55 and O80 was observed. Conclusions: Muscle loss with aging is region-specific for some muscles and uniform for others. Equivalent strength training volume at moderate or high intensities increased muscle volume with no differences in muscle volume gains for old men. These data suggest that physical exercise at moderate intensity (55 to 60% of one repetition maximum) can reverse the aging related loss of muscle mass. Trial registration: NCT03079180 in ClinicalTrials.gov. Registration date: March 14, 2017.
... As mentioned by other authors, the increase in muscle volume is not proportional to the duration of training. After 3 months of training, the increase in muscle volume becomes low or even non-existent [58]. More recently, a meta-analysis has been conducted to compare changes in strength and hypertrophy between low (≤60% of 1RM) vs. high-load (> 60% of 1RM) resistance training protocols [59]. ...