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The Effects of Protein Supplements on Muscle Mass, Strength, and Aerobic and Anaerobic Power in Healthy Adults: A Systematic Review

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Background: Protein supplements are frequently consumed by athletes and recreationally active adults to achieve greater gains in muscle mass and strength and improve physical performance. Objective: This review provides a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements accelerate gains in muscle mass and strength resulting in improvements in aerobic and anaerobic power. Evidence statements were created based on an accepted strength of recommendation taxonomy. Data sources: English language articles were searched through PubMed and Google Scholar using protein and supplements together with performance, exercise, strength, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers. Study selection: Studies recruiting healthy adults between 18 and 50 years of age that evaluated the effects of protein supplements alone or in combination with carbohydrate on a performance metric (e.g., one repetition maximum or isometric or isokinetic muscle strength), metrics of body composition, or measures of aerobic or anaerobic power were included in this review. The literature search identified 32 articles which incorporated test metrics that dealt exclusively with changes in muscle mass and strength, 5 articles that implemented combined resistance and aerobic training or followed participants during their normal sport training programs, and 1 article that evaluated changes in muscle oxidative enzymes and maximal aerobic power. Study appraisal and synthesis methods: All papers were read in detail, and examined for experimental design confounders such as dietary monitoring, history of physical training (i.e., trained and untrained), and the number of participants studied. Studies were also evaluated based on the intensity, frequency, and duration of training, the type and timing of protein supplementation, and the sensitivity of the test metrics. Results: For untrained individuals, consuming supplemental protein likely has no impact on lean mass and muscle strength during the initial weeks of resistance training. However, as the duration, frequency, and volume of resistance training increase, protein supplementation may promote muscle hypertrophy and enhance gains in muscle strength in both untrained and trained individuals. Evidence also suggests that protein supplementation may accelerate gains in both aerobic and anaerobic power. Limitations: To demonstrate measureable gains in strength and performance with exercise training and protein supplementation, many of the studies reviewed recruited untrained participants. Since skeletal muscle responses to exercise and protein supplementation differ between trained and untrained individuals, findings are not easily generalized for all consumers who may be considering the use of protein supplements. Conclusions: This review suggests that protein supplementation may enhance muscle mass and performance when the training stimulus is adequate (e.g., frequency, volume, duration), and dietary intake is consistent with recommendations for physically active individuals.
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SYSTEMATIC REVIEW
The Effects of Protein Supplements on Muscle Mass, Strength,
and Aerobic and Anaerobic Power in Healthy Adults:
A Systematic Review
Stefan M. Pasiakos Tom M. McLellan
Harris R. Lieberman
ÓSpringer International Publishing Switzerland (outside the USA) 2014
Abstract
Background Protein supplements are frequently con-
sumed by athletes and recreationally active adults to
achieve greater gains in muscle mass and strength and
improve physical performance.
Objective This review provides a systematic and com-
prehensive analysis of the literature that tested the
hypothesis that protein supplements accelerate gains in
muscle mass and strength resulting in improvements in
aerobic and anaerobic power. Evidence statements were
created based on an accepted strength of recommendation
taxonomy.
Data Sources English language articles were searched
through PubMed and Google Scholar using protein and
supplements together with performance, exercise, strength,
and muscle, alone or in combination as keywords. Addi-
tional articles were retrieved from reference lists found in
these papers.
Study Selection Studies recruiting healthy adults between
18 and 50 years of age that evaluated the effects of protein
supplements alone or in combination with carbohydrate on
a performance metric (e.g., one repetition maximum or
isometric or isokinetic muscle strength), metrics of body
composition, or measures of aerobic or anaerobic power
were included in this review. The literature search identi-
fied 32 articles which incorporated test metrics that dealt
exclusively with changes in muscle mass and strength, 5
articles that implemented combined resistance and aerobic
training or followed participants during their normal sport
training programs, and 1 article that evaluated changes in
muscle oxidative enzymes and maximal aerobic power.
Study Appraisal and Synthesis Methods All papers were
read in detail, and examined for experimental design con-
founders such as dietary monitoring, history of physical
training (i.e., trained and untrained), and the number of
participants studied. Studies were also evaluated based on
the intensity, frequency, and duration of training, the type
and timing of protein supplementation, and the sensitivity
of the test metrics.
Results For untrained individuals, consuming supple-
mental protein likely has no impact on lean mass and
muscle strength during the initial weeks of resistance
training. However, as the duration, frequency, and volume
of resistance training increase, protein supplementation
may promote muscle hypertrophy and enhance gains in
muscle strength in both untrained and trained individuals.
Evidence also suggests that protein supplementation may
accelerate gains in both aerobic and anaerobic power.
Limitations To demonstrate measureable gains in
strength and performance with exercise training and pro-
tein supplementation, many of the studies reviewed
recruited untrained participants. Since skeletal muscle
responses to exercise and protein supplementation differ
between trained and untrained individuals, findings are not
easily generalized for all consumers who may be consid-
ering the use of protein supplements.
Conclusions This review suggests that protein supple-
mentation may enhance muscle mass and performance
when the training stimulus is adequate (e.g., frequency,
volume, duration), and dietary intake is consistent with
recommendations for physically active individuals.
S. M. Pasiakos H. R. Lieberman
Military Nutrition Division, US Army Research Institute
of Environmental Medicine (USARIEM), Natick,
MA 01760-5007, USA
T. M. McLellan (&)
TM McLellan Research Inc., 25 Dorman Drive, Stouffville,
ON L4A 8A7, Canada
e-mail: DrTom.McLellan@gmail.com
123
Sports Med
DOI 10.1007/s40279-014-0242-2
Key Points
In untrained individuals, changes in lean mass and
muscle strength during the initial weeks of resistance
training are not influenced by protein
supplementation.
Protein supplementation will promote greater gains
in lean mass and muscle strength for both trained and
untrained individuals as the duration and frequency
of resistance training increases.
Presently there is some evidence to support the use
of protein supplementation to enhance gains in
aerobic and anaerobic power during the early stages
of training but the mechanisms that account for such
improvements are not well described.
1 Introduction
Protein supplements are widely consumed by athletes,
recreationally active adults, and soldiers [14], who gener-
ally believe that combining the consumption of protein
supplements with exercise will promote gains in lean mass,
resulting in improved physical performance [2,5]. This
belief is based on information typically obtained from coa-
ches, teammates, advertising, and family or friends [1,5],
and not based on understanding the peer-reviewed evidence
base for the efficacy of protein supplementation. That evi-
dence base may not be as strong as consumers assume.
There is no scientific consensus regarding performance
benefits associated with protein supplementation [6,7].
Several reports have reviewed the proposed mechanisms
associated with the intended performance benefits of pro-
tein supplementation. These reviews address whether pro-
tein supplementation alone or combined with carbohydrate
attenuates carbohydrate oxidation and hastens muscle
glycogen repletion in response to endurance-type exercise,
and particularly whether protein supplementation enhances
lean mass accretion, muscle strength, and aerobic and
anaerobic power [817]. However, the evidence that per-
formance changes are associated with these mechanisms
has not been systematically evaluated [1823], and only
two recent meta-analyses to date evaluate evidence
regarding the effects of protein supplements on actual
measures of muscle mass and strength [24,25]. Cermak
et al. [24] provided a strong evidence-based analysis to
show that protein supplementation augmented gains in lean
mass and muscle strength in both younger and older adults.
Although Schoenfeld et al. [25] also concluded that protein
supplementation augmented gains in muscle mass and
strength, their analyses focused on whether the timing of
protein ingestion was a critical factor for enhancing muscle
adaptation.
We recently published two systematic reviews that have
addressed the evidence base for the use of protein supple-
ments [26,27]. Those reviews addressed whether protein
supplementation alone or in combination with carbohydrate
accelerates glycogen repletion, thereby enhancing acute or
repeat endurance exercise performance [26], as well as the
effects of protein supplementation on muscle damage and
recovery of muscle function and physical performance [27].
This review is focused on the influence of protein supple-
ments on peripheral factors affecting muscle function and
subsequent metrics of performance. Specifically, we exam-
ined whether consuming supplemental protein facilitates
gains in muscle mass, which can increase strength and
improve aerobic and anaerobic power.
2 Methods
PubMed and Google Scholar were searched without
restriction to past publication date through to the fall of
2013 using the terms ‘protein’ and ‘supplements’ together
with ‘performance,’ ‘exercise,’ ‘competition,’ and ‘mus-
cle,’ alone or in combination as keywords. Searches were
limited to English language, peer-reviewed publications
reporting findings from healthy adults between 18 and
50 years of age who habitually consumed dietary protein at
or above the recommended dietary allowance of
0.8 gkg
-1
day
-1
[28]. Articles were also retrieved from
the reference lists of these papers and recent reviews on
protein supplements. Studies that manipulated dietary
protein and carbohydrate intake to compare the effects of
protein supplements on performance were excluded [29].
Studies that compared drink formulations that included
protein as well as vitamins and herbal supplements against
a placebo trial [3032] were also excluded since it was not
possible to isolate the effects attributed solely to protein
supplementation. Studies that combined protein supple-
mentation with creatine were excluded [3339] except
when they compared protein supplementation alone with
placebo or carbohydrate. Papers that examined the effects
of bovine colostrum [4047], b-hydroxy-b-methylbutyrate
[48], and the ingestion of single amino acids (e.g., arginine
or ornithine) were not included in this review [49]. Finally,
papers that used resistance training and supplementation
for the purpose of long-term weight management by
attempting to increase resting metabolic rate were also
excluded [50]. Only studies that reported findings with the
S. M. Pasiakos et al.
123
ingestion of various forms of protein alone or in combi-
nation with carbohydrate were reviewed.
This review first presents the literature regarding the effects
of protein supplementation on muscle mass and strength
(Sect. 3.1) for both untrained (Sect. 3.1.1) and resistance-
trained (Sect. 3.1.2) participants. Then, it discusses and
evaluates the relevant literature on aerobic and anaerobic
power (Sect. 3.2). A discussion (Sect. 4), summary evidence
statements (Sect. 5), suggestions for future research (Sect. 6)
and concluding remarks (Sect. 7) complete the paper.
3 Results
The literature search identified 32 articles incorporating
test metrics that dealt exclusively with changes in muscle
mass and strength in response to resistance training; five
articles that implemented a combined resistance and aer-
obic training program or followed participants during
sports-specific training programs, which included a mix of
training strategies and a variety of performance metrics;
and one article that evaluated muscle oxidative capacity in
response to aerobic training (Fig. 1). A strength of rec-
ommendation taxonomy (SORT) [51] was used to docu-
ment the quality of evidence for conclusions specific for
each of these categories. The SORT uses the following
criteria: (A) recommendation based on consistent and
good-quality experimental evidence; (B) recommendation
based on inconsistent or limited-quality experimental evi-
dence; or (C) recommendation based on consensus, opin-
ion, usual practice, case studies or extrapolation from
quasi-experimental research. The SORT was created to
assist medical practitioners in their assessment of patient-
oriented evidence [51]. In a similar manner, SORT can be
used to assess the evidence-based literature to provide
recommendations of protein supplement use by athletes
and recreationally active adults.
3.1 Muscle Mass and Strength
The effects of acute and chronic resistance exercise on
muscle protein turnover, and the importance of the timing
and type of protein ingestion to promote muscle protein
synthesis are well established [813,16,17,5256]. Fur-
ther, substantial evidence shows that amino acids or intact
protein supplementation stimulates protein synthesis when
consumed immediately before [57,58], during [59], or
within the first few hours after resistance exercise [5968].
However, recently it was observed that the acute protein
kinetic responses to resistance exercise and protein feeding
were not correlated to changes in lean mass and muscle
hypertrophy following 16 weeks of resistance training [69].
Thus, whether protein supplementation will promote
greater gains in metrics of performance has not been
clearly established.
3.1.1 Studies in Untrained Participants
3.1.1.1 Studies Assessing Protein Versus Non-Energetic
Placebo Several studies have examined the effects of
protein supplements versus non-energetic placebos on
muscle mass and strength using untrained individuals. The
results from these studies have been inconsistent. For
example, in untrained individuals, Antonio et al. [70] found
no effects of protein supplementation on measures of
muscle mass and strength following a 6-week combined
aerobic and resistance training program. Similarly, Erskine
et al. [71] reported no effect of protein supplementation
following 12 weeks of resistance training of the elbow
flexors. In contrast, an early study by Fern et al. [72]
reported greater gains in muscle mass following 4 weeks of
resistance training for those participants consuming an
additional 2 gkg
-1
of protein powder daily. Unfortunately,
this study did not include a measure of strength. In addi-
tion, Hulmi et al. [73] demonstrated enhanced muscle
hypertrophy when whey protein was consumed immedi-
ately before and after bi-weekly resistance training sessions
for 21 weeks. In addition, protein supplementation atten-
uated post-exercise myostatin messenger RNA (mRNA)
expression and increased cyclin-dependent kinase 2 sig-
naling, suggesting that protein supplementation may
potentiate cell growth in response to resistance exercise.
Despite concomitant gains in muscle mass and anabolic
gene expression, protein supplementation was not associ-
ated with consistent gains in strength. Post-training muscle
strength was similar between protein and placebo for all
measures of isometric and dynamic leg strength, but leg
extension force and isometric bench press were greater
with protein. As such, the effect of protein supplementation
when compared with a non-energy providing placebo on
resistance training-induced gains in muscle and strength in
untrained adults remains unclear.
3.1.1.2 Studies Assessing Protein Versus Carbohy-
drate It has been hypothesized that supplemental energy
from carbohydrate in combination with resistance exercise
can produce similar gains in muscle mass and strength in
untrained individuals to those produced by consuming
supplemental protein. For example, consuming an energy-
matched protein or carbohydrate supplement before and
after resistance training 3 daysweek
-1
for 14 weeks pro-
duced similar improvements in isometric and isokinetic
peak torque (slow velocity) and countermovement jump
height [74]. However, squat jump performance, as well as
the change in type I and II muscle fiber cross-sectional
area, improved more with protein than carbohydrate
Protein Supplements and Exercise Performance
123
supplementation. Coburn et al. [75] also demonstrated
greater gains in skeletal muscle strength and cross-sec-
tional area for volunteers who consumed a leucine/whey
protein supplement versus volunteers who consumed an
energy-matched carbohydrate supplement during an
8-week (3 daysweek
-1
) resistance training program.
Willoughby et al. [76] evaluated changes in muscle
mRNA myosin gene expression, total myofibrillar protein
content, body composition and muscle strength in response
to 10 weeks of alternating upper and lower body resistance
exercises 4 daysweek
-1
, with a whey, milk, casein and
free amino acid protein mixture or an energy-matched
carbohydrate supplement consumed 1 hour before and
immediately after each session. Total and lean body mass
increased in both groups. However, increases in muscle
strength were greater for those supplemented with protein
than carbohydrate. Changes in myofibrillar protein content
and myosin mRNA expression were also greater with
protein than carbohydrate supplementation.
Weisgarber et al. [77] hypothesized that providing a
protein supplement immediately prior to exercise and
during training after each set of exercise would provide an
optimal stimulus for muscle protein synthesis and gains in
muscle hypertrophy and strength over time. However,
following 8 weeks of training four times a week, gains in
muscle strength were similar for those receiving protein or
isocaloric carbohydrate and neither group showed gains in
lean mass. Reductions in protein, carbohydrate and total
caloric intake over the course of the training program were
present in both groups, which may have compromised the
potential benefits of the supplementation with training.
The effects of protein supplementation on muscle mass
and strength may differ based upon resistance training
volume, as the skeletal muscle protein synthetic response to
resistance exercise varies in magnitude and duration when
the volume and length of time the muscle is under tension
are manipulated [7880]. Mielke et al. [81] compared the
effects of a leucine-enriched whey protein supplement
versus not only an energy-matched carbohydrate supple-
ment but also a non-energetic placebo. The supplements
were provided immediately before and after resistance
exercise performed three times per week for 8 weeks. The
volume of resistance exercise for volunteers consuming
protein and carbohydrate was low (one set of 6–8 repeti-
tions of bench press and leg extension). Those consuming
the non-energetic placebo completed two sets of each
Records identified through
database searching
(n = 53)
Additional records identified
through other sources
(n = 24)
Records after duplicates removed
(n = 77)
Records screened
(n = 77)
Records excluded (n =17)
Reviews (n = 15)
Position stands (n = 2)
Full-text articles
assessed for eligibility
(n = 60)
Full-text articles excluded, with
reasons (n = 22)
Dietary manipulation (n = 1)
Included vitamins and herbals
(n = 3)
Included creatine (n = 7)
Included bovine colostrum (n
= 8)
-hydroxy- -
methylbutyrate (n = 1)
Included single amino acids
arginine or ornithine (n = 1)
Purpose of supplementation
was for weight control (n = 1)
Studies included in
qualitative synthesis
(n = 38)
Fig. 1 Study selection and flow
diagram of articles included in
the review
S. M. Pasiakos et al.
123
exercise (6–8 repetitions). Body and lean mass were not
affected by training regardless of group assignment and
there was no difference among the groups in gains in
muscle strength. Thus, despite the smaller volume of
training for those groups receiving supplements, either
protein or carbohydrate, they improved similarly to those
receiving no supplement. However, the low training vol-
ume for all groups and the lack of change in lean mass
suggest the training stimulus was inadequate. Further, this
study did not include a placebo group that performed only
one set of each exercise so comparisons with groups
receiving supplements are not directly comparable.
3.1.1.2.1 Type of Protein Versus Carbohydrate. Protein
source may be particularly important to promote gains in
muscle mass and strength, as the digestive properties and
essential amino acid (EAA) profile (particularly leucine) of
various proteins modulate skeletal muscle protein synthetic
responses to exercise [55]. For example, Candow et al. [82]
compared the effects of whey or soy protein versus car-
bohydrate supplementation during a 6-week resistance
training program on body composition and muscle
strength. Increases in lean mass and 1 repetition maximum
(RM) bench press and squat strength increased significantly
more for both protein groups compared with those
receiving carbohydrate. The authors suggested that protein
supplementation (whey and soy) increased muscle protein
synthesis independent of source, which contributed to the
observed gains in lean mass and muscle strength as com-
pared with carbohydrate. These findings are somewhat
surprising given that muscle protein synthesis in recovery
from resistance exercise is generally greater after con-
suming whey versus soy [83], an effect attributed to the
higher leucine content and digestive properties of whey
protein [84]. However, as acknowledged by Candow et al.
[82], since daily dietary protein intake was high, the timing
of protein supplementation immediately before and after
the training [57,60,62] may have been more important
than the type of protein ingested.
Similarly, Volek et al. [85] compared whey versus soy
protein supplementation for gains in lean mass and
muscle strength but the resistance training program was
extended for a much longer period (9 months) compared
with the majority of other studies. Supplementation was
isonitrogenous (whey vs soy) and isocaloric (with the
carbohydrate only as placebo) and was provided after the
exercise sessions on training days or in the morning on
non-training days. Gains in lean mass were greater with
the whey supplement but gains in 1 RM bench and leg
press strength were similar among all groups. The
authors suggested the gains in lean mass were likely
distributed over the whole body given the number of
different exercises performed during the training sessions
and these changes were unlikely to impact strength
during a single specific movement.
Herda et al. [86] examined whether whey protein, with
specifically modified properties of absorption through
polyethylene glycosylation, promoted greater resistance
training adaptations than standard whey protein following
an 8-week program involving three weekly exercise ses-
sions. The study design also included a placebo group
receiving isocaloric carbohydrate and a non-supplemented
control group. All supplements were provided before and
immediately following exercise on training days but only
one supplement dose was provided in the morning on non-
training days. The whey supplements were not isonitroge-
nous as the modified whey product contained an additional
7 g of leucine with each serving in addition to the 20 g of
whey protein. Regardless of whether participants received
a supplement and regardless of the type of supplement, all
groups showed equal gains in lean mass and muscle cross-
sectional area, and similar improvements in bench and leg
press strength and muscle endurance.
3.1.1.3 Studies Assessing Combined Protein and Carbo-
hydrate Results from studies examining the combined
effects of carbohydrate and protein on indices of muscle
strength and hypertrophy in untrained adults have been
inconclusive. For example, increased muscle strength in
untrained adults following 10 weeks (5 daysweek
-1
)of
alternating one-legged exercise training were not affected
by combined carbohydrate and protein supplementation in
a study by Williams et al. [87]. However, because the
carbohydrate ?protein supplement was always ingested
after training the same leg, but not ingested when the other
leg was trained, a carry-over effect of supplementation on
the non-supplemented leg during the initial stages of
training could not be discounted. Tang et al. [88] reported
that rates of muscle protein synthesis were still elevated
70 % versus baseline levels 28 hours after an acute bout of
resistance exercise in untrained participants.
Using a more traditional whole-body resistance training
model, Bird et al. [89] studied the combination of carbo-
hydrate ?EAA on changes in body composition, muscle
fiber cross-sectional area and muscle strength, measured
throughout 12 weeks of resistance training 2 daysweek
-1
.
Supplementation with carbohydrate, EAA, carbohy-
drate ?EAA, or placebo was provided throughout the
training sessions. Muscle isokinetic leg strength increased
similarly for all groups in response to training. Lean mass
and muscle fiber type I and II cross-sectional area also
increased in all groups, but gains in muscle mass and cross-
sectional area were greatest in those consuming the com-
bined carbohydrate and EAA supplement. The authors
attributed the greater gains in muscle mass for those con-
suming carbohydrate ?EAA to the well documented
Protein Supplements and Exercise Performance
123
anabolic effects of protein supplementation on muscle
protein turnover. Nevertheless, greater gains in muscle
mass did not result in greater gains in muscle strength.
Similarly, Vieillevoye et al. [90] compared the effects of
a carbohydrate ?EAA supplement versus carbohydrate
alone on measures of muscle architecture, strength and
body composition following 12 weeks of resistance train-
ing twice a week. Supplementation was provided twice
daily with one dose occurring immediately following
exercise during training days. Although both muscle
thickness and angle of pennation for the gastrocnemius
medialis determined through ultrasound scans increased
more for the carbohydrate ?EAA group, changes in lean
mass and improvements in maximal isokinetic force during
bench press and leg squat exercise were similar between
groups. Interestingly, only one participant was in negative
nitrogen balance prior to the start of the program, sug-
gesting that the initial protein intake, which averaged
1.3 gkg
-1
, was adequate without additional
supplementation.
Olsen et al. [91] examined the effects of a protein and
carbohydrate supplement versus carbohydrate alone on
growth and proliferation of muscle satellite cells and
myonuclei throughout 16 weeks of resistance training three
times a week. Protein supplementation was only provided
on training days immediately before and following the
workout. Those receiving protein and carbohydrate showed
a greater increase in the number of satellite cells and
myonuclei per fiber, but improvements in maximal iso-
metric leg extension force were similar between supple-
ment groups.
3.1.1.3.1 Milk and Dairy Products as a Supplement. The
study of milk as an inexpensive, high-quality pro-
tein ?carbohydrate supplement has increased dramati-
cally in recent years. Walberg-Rankin et al. [92] compared
the effects of an energy-matched carbohydrate or low-fat
milk supplement consumed following resistance training
(3 daysweek
-1
for 10 weeks). Improvements in body
composition and muscle strength were statistically similar
between groups, although mean gains in lean mass tended
to be higher with milk (1.6 kg) than the energy-matched
carbohydrate control (0.8 kg). Regardless, adaptations to
this 10-week resistance training program in previously
untrained males were not significantly influenced by
supplementation.
Hartman et al. [93] compared the effects of an energy
and carbohydrate-matched fat-free milk and soy pro-
tein ?carbohydrate supplementation in response to
12 weeks of resistance training 5 daysweek
-1
in a group
of untrained men. A control group consumed an energy-
matched carbohydrate-only supplement. Lean mass
increased in all groups. However, mean gains in muscle
mass were more pronounced with milk supplementation
(6.2 %) compared with the other treatments (3.7 and 4.4 %
for control and soy, respectively), and milk tended
(p\0.1) to improve muscle strength (mean changes of
102, 67 and 62 % for leg press, knee extension and ham-
string curls, respectively) more than soy protein ?carbo-
hydrate (98, 60 and 42 %, respectively, for the same
exercises above) and carbohydrate alone (87, 46 and 51 %,
respectively). In addition, the cross-sectional area of type II
fibers in the vastus lateralis increased in all groups but
gains in muscle size were greatest for those supplemented
with milk. The authors suggested that having subjects train
for 12 rather than 10 weeks and perform five rather than
three sessions per week could explain the lack of support
for milk supplementation observed with the study from
Walberg-Rankin et al. [92]. As such, the findings by
Hartman et al. [93] support the view that combining protein
supplementation in the form of fat-free milk with an ade-
quate resistance-training stimulus in previously untrained
adults elicits greater rates of protein accretion compared
with soy protein and carbohydrate supplementation alone.
In a subsequent study, the combined effects of resistance
exercise with milk or energy-matched carbohydrate sup-
plementation for inducing changes in body composition
and muscle function in women were examined by Josse
et al. [94] during 12 weeks of training. The training pro-
gram and testing protocol were identical to one previously
used by this same laboratory to study training adaptations
in males [93]. Lean mass increased and fat mass decreased
significantly more with women receiving milk than women
receiving carbohydrate. In contrast to Hartman et al. [93],
the women consuming milk experienced significantly
greater gains in muscle strength as compared with women
consuming carbohydrate alone, which was attributed to the
lower relative upper body strength (i.e., per kg body mass)
for the untrained women compared with men.
White et al. [95] also examined whether yogurt was
more effective than whey protein or isocaloric carbohy-
drate in promoting gains in lean mass and strength in
previously untrained women. One supplement dose
equivalent to one serving of yogurt, which contained 5 g of
protein, was provided immediately following the three
whole-body resistance training sessions for 8 weeks. In
addition, those receiving yogurt consumed a total of three
servings per day throughout the study protocol. Conse-
quently, total caloric intake and total protein intake were
greater for those receiving yogurt than the other groups.
Nonetheless, regardless of supplement provided after
training, all groups showed equal gains in lean mass and
improvements in muscle strength.
3.1.1.4 Summary: Untrained Participants An overview
of the findings from the subsections for untrained
S. M. Pasiakos et al.
123
participants is presented in Table 1and a subsequent
detailed list of the findings for protein supplements is
provided in Table 2. Protein supplementation likely has no
effect on lean mass and strength when training programs
last 8 weeks or less [70,77,81,86,95,96]. It has not been
possible to determine whether there is a relationship
between gains in muscle strength due to protein supple-
mentation and muscle hypertrophy in training programs
lasting either less than [7375,82,89,9294] or more than
8 weeks when training sessions per week were limited [73,
87,89,90]. However, substantially increasing the fre-
quency or duration of exercise, or manipulating both in
combination with protein supplementation does appear to
enhance gains in muscle mass and measures of muscle
strength in untrained individuals [76,82,85,91,93,94], a
view that is consistent with findings from a recent meta-
analysis [24]. Assuming the training program is of suffi-
cient intensity, frequency, and duration [93,94], and die-
tary protein intake is more than adequate for physically
active adults [76,82], protein supplementation may
enhance gains in muscle mass, strength, and myofibrillar
protein synthesis regardless of protein source (e.g., whey,
soy, and milk) [82,93,94].
3.1.2 Resistance-Trained Participants
Athletes who regularly engage in strength and explosive
power exercise are experienced with resistance-training
exercise. Therefore, in training studies, changes in outcome
measures of muscle mass and strength exhibited by these
individuals are less likely to reflect the confounding effects
of neural adaptations evident during early stages of training
with untrained individuals [97,98]. As a consequence, the
modulating effects of dietary protein supplementation on
adaptations to training may be more readily apparent with
trained participants than in studies of untrained individuals.
In addition, resistance training attenuates the duration of
the increased rate of muscle protein synthesis following
exercise [88,99] but the increase in muscle protein syn-
thesis is most evident in the myofibrillar component [100].
As a result, one might expect protein supplementation to
provide greater changes in muscle mass and strength for
resistance-trained participants when provided in close
proximity to the training stimulus.
3.1.2.1 Studies of Protein Supplementation During Over-
training Alternating periods of high-volume (i.e., over-
training) and low-volume training is a common practice
among trained individuals attempting to enhance perfor-
mance. Fry et al. [101] examined whether daily protein
supplementation impacted performance more than a pla-
cebo in elite weightlifters during 1 week of high-volume
training. No effects of protein supplementation were
observed. However, both the protein (mean 2.4 gkg
-1
)
and placebo (mean 2.2 gkg
-1
) groups consumed high
protein diets. Ratamess et al. [102], and a subsequent paper
by Kraemer et al. [103], investigated the use of an amino
acid supplement during 4 weeks of high-volume (10–12
Table 1 An overview of the effects of protein supplementation for the different subsections reviewed for untrained participants
Type of study Effect of protein
supplementation
Note
PRO versus PLA $mass, strength (2)
:mass (2)
$strength (1)
Low training volume, small muscle mass recruited and lack of strength metric
PRO versus CHO :CSA, $strength (1)
:CSA, strength (1)
$mass, :strength (1)
$mass, strength (2)
Change in normal dietary protein during training, lack of proper placebo control
PRO type versus
CHO
:mass, strength (1)
:mass, $strength (1)
$mass, strength (1)
High normal dietary protein intake indicated timing of supplement ingestion was
important
PRO ?CHO $mass, strength (2)
:mass, $strength (1)
:myonuclei, $strength (1)
High normal dietary protein, carry-over effects to non-supplemented limb
Milk products $mass, strength (2)
:mass, strength (2)
Low PRO dose, greater frequency and duration of training associated with improvements
with milk
The numbers in parentheses refer to the number of studies. The arrows indicate whether the protein supplement increased (:) or had no additional
($) effect
CHO carbohydrate, CSA cross-sectional area, PLA placebo, PRO protein
Protein Supplements and Exercise Performance
123
Table 2 A summary of the performance outcomes for lean mass and muscle strength for those studies with protein and/or carbohydrate supplements that recruited untrained participants
Study Training program Supplementation Performance outcomes
Intensity Frequency
(9/week)
Duration
(weeks)
Andersen et al. [74] 3–4 sets, 4–15 reps, 4 leg
exercises
3 14 25 g PRO or CHO pre/post-training and non-
training AM
PRO [CHO for CSA, vertical jump
PRO =CHO for IKST
Antonio et al. [70] 3 sets 6–12 reps, 6–7
exercises
3 6 12.8 g EAA pre/post-training ?12.8 g non-
training AM
EAA =PLA for # reps bench press
Bird et al. [89] 3 sets, 8–10 reps @ 75 %
1RM for 8 exercises
2 12 6 g EAA, 6 % CHO, 8.5 mL/kg divided into 25
servings throughout exercise
CHO ?EAA [PLA for LBM
CHO ?EAA [other groups for type II CSA
CHO ?EAA [PLA for leg press
All groups =for IKST
Candow et al. [82] 4–5 sets 6–12 reps @
60–90 % 1 RM, 6–9
exercises
6 6 0.4 g/kg PRO ?0.1 g/kg CHO, 0.5 g/kg CHO
for PLA pre/post-training ?PM, non-training
AM/29PM
[Whey =soy] [PLA for LBM and 1 RM for both
squat and bench press
Coburn et al. [75] 3–5 sets, 6 reps @ 80 % 1
RM leg extension
3 8 20 g whey ?6.2 g leucine pre/post-
training ?non-training AM, isocaloric CHO
PRO [CHO [CON for 1 RM
PRO =CHO =CON for LBM
[PRO =CHO] [CON for CSA
Erskine et al. [71] 2–3 sets, 8–10 reps, 2 arm
curl exercises
3 12 20 g whey pre/post-training PRO =PLA for 1 RM, isometric force, angle of
pennation, muscle size, EMG agonist/antagonist
activation
Fern et al. [72] Specific details not stated 3 4 2 g/kg PRO daily, PLA PRO [PLA for gains in lean mass
Hartman et al. [93] 2–4 sets, 6–12 reps @ 80 %
1RM for 4–5 exercises
51229500 mL milk, soy or PLA 0 and 1 h post-
exercise
Milk [[soy =PLA] for LBM
Milk [[soy =PLA] (p\0.1) for 1 RM of leg
exercises
Milk [[soy =PLA] for type II of CSA
[milk =soy] [PLA for type I CSA
Herda et al. [86] 1–5 sets, 6 reps at 80 % 1
RM for bench and leg
press
3 8 Specifically modified whey (20 g ?7g
leucine), standard whey (20 g), PLA (27 g
CHO) pre/post-training and 1 dose AM non-
training
Modified whey =whey =PLA for gains in lean mass,
improvements in 1 RM leg and bench press, and reps
to failure at 80 % 1 RM
Hulmi et al. [73] 2–5 sets, 6–20 reps,
40–85 % 1 RM for 12–14
exercises
2 21 15 g whey pre/post-training PRO [PLA for CSA of vastus lateralis, molecular
signals of cell growth
PRO =PLA for 1 RM leg press and isometric leg and
bench press
Josse et al. [94] 2–4 sets, 6–12 reps @ 80 %
1 RM for 4–5 exercises
51229500 mL milk or CHO 0 and 1 h post-
exercise
Milk [CHO for LBM and 1 RM bench press
Mielke et al. [81] 1 set 8 reps @ 80 % 1 RM
for leg, chest, PLA 2 sets
3 8 20 g whey ?6.2 g leucine pre/post-
training ?non-training AM/PM, isocaloric
CHO
PRO =CHO =PLA for LBM, 1 RM leg, chest
S. M. Pasiakos et al.
123
Table 2 continued
Study Training program Supplementation Performance outcomes
Intensity Frequency
(9/week)
Duration
(weeks)
Olsen et al. [91] 3–5 sets, 6–12 reps of 3 leg
exercises
3 16 20 g PRO ?60 g CHO, PLA (80 g CHO) pre/
post-training, CON (no training)
PRO ?CHO [PLA for satellite cells and myonuclei
per fiber
[PRO ?CHO =PLA] [CON for isometric MVC
Vieillevoye et al. [90] Several sets combined for
50 reps at 70–85 % 1 RM
for 5 exercises
2 12 15 g EAA ?15 g CHO, PLA (30 g CHO) pre/
post-training or twice in AM non-training
EAA ?CHO =PLA for gains in lean mass or
increases in maximal isokinetic force during squat or
bench press
EAA ?CHO [CHO for muscle thickness and angle of
pennation
Volek et al. [85] 3–5 sets, 3–15 reps for 11
exercises
3 36 Whey (21.6 g ?CHO), soy (20 g ?CHO),
PLA (CHO) pre/post-training and AM on non-
training
Whey [[soy =PLA] for gains in lean mass
Whey =soy =PLA for 1 RM squat and bench press
Walberg-Rankin et al.
[92]
3–5 sets, 3–12 reps @
55–97 % 1 RM for 7
exercises
3 10 Milk (0.21 g/kg PRO ?0.92 g/kg CHO),
1.25 g.kg CHO post-training
Milk =CHO for LBM and all 1 RM exercises
Weisgarber et al. [77] 3 sets, 6–10 reps for 9
exercises
4 8 0.3 g/kg PRO, PLA (0.3 g/kg CHO) PRO =PLA for LBM and gains in 1 RM bench press
White et al. [95] Sets and reps not stated for
9 exercises
38396 oz/day yogurt with 1 serving post-exercise
(20 g CHO, 5 g PRO), PRO ?CHO, PLA
(CHO) post-exercise only
Yogurt =PRO ?CHO =PLA for gains in LBM and
increases in 1 RM bench and leg press
Williams et al. [87] 4 sets, 10 max reps,
unilateral leg extension
5 (alternating
leg)
10 0.2 g/kg PRO ?0.8 g/kg CHO post-training [CHO ?PRO =PLA] [CON for IMST, IKST, 1 RM
CHO ?PRO =PLA =CON for LBM
Willoughby et al. [76] 3 sets, 6–8 reps @ 85 % 1
RM for 4–6 exercises
4 10 14 g PRO ?6 g AA or 20 g CHO pre/post-
exercise, 40 g non-training AM
PRO [CHO for LBM, 1 RM leg and bench press,
myofibrillar PRO, myosin heavy chain
AA amino acid, AM morning, CHO carbohydrate, CON control, CSA cross-sectional area, EAA essential amino acid, EMG electromyogram, IKST isokinetic strength, IMST isometric strength,
LBM lean body mass, max maximum, MVC maximal voluntary contraction, PLA placebo, PM afternoon, PRO protein, reps repetitions, RM repetition maximum
Protein Supplements and Exercise Performance
123
repetitions) training and a subsequent 2-week low-volume
(3–5 repetitions) training period. Protein supplementation
attenuated the initial declines in muscle strength and power
observed after the first week of high-volume training.
However, changes in strength and power during the
remaining 3 weeks of the high-volume training period
were not different between the protein and placebo groups.
During the subsequent 2-week period of low-volume
training, increases in bench press strength for placebo were
actually greater than protein. The authors concluded that
protein supplementation was beneficial because it limited
reductions in muscle strength and power that occurred
during the early stages of adaptation to the overtraining
program. However, during the later stages of the over-
training program, and subsequently, during the period of
reduced training volume, protein supplementation had no
influence on gains in muscle strength and power.
3.1.2.2 Studies of Protein Versus Isocaloric Carbohy-
drate Burke et al. [104] examined changes in body
composition and muscle strength over a period of 6 weeks
of resistance training, during which whey protein or car-
bohydrate supplementation was provided. Training con-
sisted of high-volume and high-resistance 3-day blocks
followed by 1 day of rest. Change in lean mass during the
training and supplementation period was greater for protein
than carbohydrate. However, both bench press and leg
squat increased similarly for protein and carbohydrate
during the training and supplementation period. Protein
was associated with greater gains in isokinetic knee
extension but not flexion torque. These data suggest whey
protein supplementation may accelerate gains in lean mass
during resistance training. However, these data also show
that during the initial weeks of training, changes in lean
mass are not necessarily reflected in appreciable gains in
muscle strength.
The effects of whey protein or carbohydrate supple-
mentation during 11 weeks of resistance exercise were
reported by Cribb et al. [105]. Lean mass increased in both
the whey protein (mean ?2.3 kg) and carbohydrate (mean
?0.7 kg) groups during training. However, the increase in
lean mass for protein was not statistically different than for
carbohydrate, possibly because sample size of the groups
(n=5) was too small. However, in contrast to the findings
above by Burke et al. [104], improvements in muscle
strength were greater for individuals consuming protein
versus carbohydrate. Changes in muscle cross-sectional
area also tended (p\0.08) to be greater with protein,
which was positively associated (0.8 \rB0.85 for the
different fiber types) with muscle strength.
3.1.2.3 Studies of Protein Versus Protein and Carbohy-
drate A subsequent study by Cribb et al. [106] compared
the effects of a combined protein ?carbohydrate supple-
ment with protein alone on lean mass and strength changes
during resistance training. The supplements were energy-
matched but provided different levels of protein (0.6 vs
1.3 gkg
-1
for the protein ?carbohydrate and protein
supplements, respectively). Increases in lean mass and
muscle strength (e.g., bench press, squats, and pull-downs)
were similar between groups. There were also no differ-
ences between groups in the increase in muscle fiber type
cross-sectional area or total muscle contractile protein
content. Consistent with earlier findings [105], these data
also revealed a positive relationship between changes in
cross-sectional area and gains in muscle strength. Collec-
tively, the reports by Cribb et al. [105,106] suggest that
protein not carbohydrate provides the stimulus for muscle
fiber hypertrophy during resistance training. These data
also suggest that daily protein supplementation above
0.6 gkg
-1
may not be necessary, especially when mean
daily intake of dietary protein without supplementation was
already at or above 1.6 gkg
-1
[105,106].
3.1.2.4 Studies of Protein Source and Protein Combina-
tions Whey and casein protein have differences in
digestion rates and absorption kinetics that differentially
affect muscle protein synthesis [83]. As a result, Cribb
et al. [107] compared the effects of supplemental whey or
casein protein on body composition and muscle strength in
response to a 10-week training program. Individuals con-
suming whey protein increased lean mass and decreased fat
mass more than those who consumed casein. In addition,
gains in muscle strength were also significantly greater for
those receiving whey.
Comparisons of whey and casein protein supplementa-
tion for resistance-trained female athletes were also studied
by Wilborn et al. [108]. Supplementation was provided
before and after training, which consisted of whole-body
resistance training 4 days per week and skills training three
times per week for 8 weeks. However, in contrast to the
findings above [107], gains in lean mass and improvements
in muscle strength and power were similar between groups,
regardless of the type of protein provided with training
[108].
Isonitrogenous animal (whey) versus plant (rice) protein
sources have also been studied as supplements provided
immediately following strength training sessions conducted
four times per week for 8 weeks in participants already
engaged in resistance training [109]. Both groups demon-
strated equal gains in lean mass and improvements in
muscle strength and power. Although the amino acid pro-
file varied somewhat between supplements, the authors
argued that the high dose of rice protein (48 g) provided
sufficient EAA to stimulate muscle protein synthesis
equally to the whey supplement, even though the latter had
S. M. Pasiakos et al.
123
a greater EAA content. However, these statements were not
supported with direct measurements of muscle protein
synthesis.
Colker et al. [110] compared the effects of a daily whey
supplement alone or in combination with branched chain
amino acids (BCAA; leucine, isoleucine, and valine) and
glutamine. They observed greater increases in muscle
strength and endurance and greater increases in lean mass
over 10 weeks of 3 daysweek
-1
training when supple-
ments included BCAA and glutamine, improvements the
authors attributed to the additional leucine content of the
combined supplement. Unfortunately, muscle endurance
was higher at baseline for those receiving the additional
BCAA and glutamine, which confounds the changes that
were noted in response to training.
It is important to note that none of the studies above
[107110] included a placebo or control group in their
experimental design. Thus, their findings whether sup-
portive [107,110] or not [108,109] for a particular source
of protein are qualitatively less conclusive because of this
design limitation.
Other studies have assessed whether manipulating the
source of high-quality protein with additional BCAA and
glutamine altered body composition and muscle strength
responses to training. For example, Kerksick et al. [111]
assessed the effectiveness of a mixture of whey protein
together with either casein or glutamine and BCAA
versus an energy-matched carbohydrate supplement on
changes in body composition and muscle strength fol-
lowing a 10-week training program. Lean mass increased
more for those supplementing with whey and casein but
there were no differences among groups in the increases
in bench or leg press strength resulting from training.
These findings suggest that type of protein supplement
consumed may impact changes in lean mass by provid-
ing sufficient amino acids necessary to maximize muscle
protein synthesis. However, dietary energy and protein
intake varied between groups. Thus, the effects of pro-
tein supplementation versus overall dietary protein intake
could not be determined.
3.1.2.5 Studies of Protein Timing Although the impor-
tance of protein supplementation in close proximity to the
exercise stimulus for enhancing muscle protein synthesis in
trained participants has been well documented [88,99],
there has been only one study that has examined the timing
of protein ingestion together with metrics of muscle
strength for resistance-trained participants. Hoffman et al.
[112] compared the effects of protein supplementation
provided in the morning and evening or immediately
before and after workouts, which occurred four times
weekly for 10 weeks. Supplementation also occurred at the
same time of day during the three non-training days and
there was a control group that did not receive supplemen-
tation. There were no differences among the groups,
regardless of supplementation or its timing, on changes in
muscle strength or power. The authors suggested that
supplementation did not enhance performance gains since
the athletes were in positive nitrogen balance at the
beginning of the study and consumed high daily dietary
protein ([1.6 gkg
-1
).
3.1.2.6 Summary: Resistance-Trained Participants An
overview of the findings from the subsections on resis-
tance-trained participants is presented in Table 3and a
subsequent detailed list of the findings for protein supple-
ments is provided in Table 4. Protein supplements had little
or no effect on measures of strength and body composition
when programs were 4 weeks or less [101103], whereas
positive effects of protein supplements have been observed
on changes in lean mass and/or muscle strength when
training programs were 8 weeks or longer [105111]. The
addition of carbohydrate to protein does not appear
advantageous [106], whereas the addition of casein or
Table 3 An overview of the effects of protein supplementation for the different subsections reviewed for resistance-trained participants
Type of study Effect of protein supplementation Note
PRO versus PLA $mass, strength (2)
$strength (1)
Increased training intensity only 1–4 weeks’ duration
PRO versus CHO :mass, $strength (1)
$mass, :strength (1)
Low participant numbers
PRO type :mass, strength (2)
:mass, $strength (1)
$mass, strength (2)
No placebo control, high supplemental dose of leucine regardless of source
PRO ?CHO versus PRO $mass, strength (1) High normal dietary protein, no placebo control
PRO timing $mass, strength (1) High normal dietary protein
The numbers in parentheses refer to the number of studies. The arrows indicate whether the protein supplement increased (:) or had no additional
($) effect
CHO carbohydrate, PLA placebo, PRO protein
Protein Supplements and Exercise Performance
123
Table 4 A summary of the performance outcomes for lean mass and muscle strength for those studies with protein and/or carbohydrate supplements that recruited resistance-trained
participants
Study Training program Supplementation Performance outcomes
Intensity Frequency Duration
(weeks)
Burke et al. [104] 6–12 reps/4–5 sets for several
exercises
3 days on/1
off
6 1.2 g/kg/day whey or CHO divided in 4
doses
Whey [CHO for LBM
Whey =CHO for 1 RM bench press and squat
Whey [CHO for knee extension
Colker et al.
[110]
8–12 reps/set for several
exercises
39/week 10 40 g/day whey, 3 g/day BCAA ?5g/
day glutamine
Whey ?BCAA ?glutamine [whey for LBM, bench press reps
Cribb et al. [107] 2–4 sets, 4–10 reps, 70–95 %
1RM
39/week 10 1.5 g/kg/day PRO in 3–4 servings Whey [casein for LBM and all 1 RM
Cribb et al. [105] 2–4 sets, 4–10 reps, 70–95 %
1RM
39/week 10 1.3 g/kg/day PRO or CHO divided in 3
doses
PRO =CHO for LBM
PRO [CHO for 1 RM
Cribb et al. [106] 2–4 sets, 4–10 reps, 70–95 %
1RM
3x/week 10 1.3 g/kg/day PRO, 0.6 g/kg/day
PRO ?0.7 g/kg/day CHO divided in 3
doses
PRO =PRO ?CHO for LBM and 1 RM
Fry et al. [101] 70–100 % 1RM for several
exercises
79/week,
39/day
1 2.4 g AA 39/day with meals ?2.1 g
BCAA pre-training
PRO =PLA for vertical jump and 1 RM for snatch
Hoffman et al.
[112]
3–4 sets, 6–10 reps for several
exercises
49/week 10 42 g collagen, whey and casein mix AM/
PM, pre/post-exercise or CON
AM/PM =pre/post =CON for change in 1 RM and power for
squat and bench, and LBM
Joy et al. [109] 3–5 sets, 2–12 reps for several
exercises
49/week 8 48 g whey or rice PRO post-exercise Whey =rice for gains in lean mass, 1 RM leg and bench press, and
leg power
Kerksick et al.
[111]
3 sets, 6–10 reps to fatigue,
7–8 exercises
49/week 10 40 g whey ?5 g glutamine ?3g
BCAA, 40 g whey ?8 g casein, 48 g
CHO within 2 h post-exercise, non-
training AM
Whey ?casein [[whey ?BCAA ?glutamine =CHO] for
LBM
Whey ?casein =whey ?BCAA ?glutamine =CHO for 1
RM and # reps
Kraemer et al.
[103]
3–5 sets, 3–12 reps for 5–8
exercises
49/week 4 0.4 g/kg/day AA in 3 doses PRO =PLA for 1 RM bench and squat at 4 weeks
Ratamess et al.
[102]
3–5 sets, 3–12 reps for 5–8
exercises
49/week 4 0.4 g/kg/day AA in 3 doses PRO =PLA for 1 RM bench and squat at 4 weeks
PRO =PLA for LBM
Wilborn et al.
[108]
1–3 sets, 12–15 reps for
several exercises
49/week 8 24 g whey or casein pre/post-exercise Whey =casein for gains in LBM, 1 RM and reps to failure for
bench and leg press
AA amino acid, AM morning, BCAA branched chain amino acid, CON control, CHO carbohydrate, LBM lean body mass, PLA placebo, PM evening, pre before exercise, post immediately after
exercise, PRO protein, reps repetitions, RM repetition maximum
S. M. Pasiakos et al.
123
BCAA to whey protein may lead to greater gains in lean
mass and strength [110,111], but there may be a ceiling to
the beneficial effect from the additional source of protein
[109].
3.2 Concurrent Training for Enhancement of Aerobic
and Anaerobic Power
This section of the review addresses the issue of whether
protein supplementation reliably enhances aerobic or
anaerobic performance when training is being conducted
concurrently to enhance both parameters. Success in many
sports requires that athletes not restrict their training to
resistance exercise but instead train to augment both aer-
obic and anaerobic power as well as muscular strength. In
theory, the use of protein supplements could assist with the
diverse training adaptations required to be successful in
various sporting activities. For example, Wilkinson et al.
[113] demonstrated, with use of a one-legged resistance or
endurance training model, that increases in mitochondrial
protein synthesis were confined to the endurance-trained
leg following 10 weeks of a regular training program.
Since protein supplementation augments rates of muscle
protein synthesis following endurance exercise [114], it is
conceivable supplementation during repeated training ses-
sions could further stimulate mitochondrial adaptations
[113]. However, potential benefits of protein supplements
following endurance exercise might only be evident during
the initial period of training as Breen et al. [115] reported
no effect of supplementation in well trained cyclists on
rates of mitochondrial protein synthesis following 90
minutes of exercise. To our knowledge, studies have not
considered whether repeated use of protein supplements
following sprint or high-intensity anaerobic training might
increase muscle buffering capacity or synthesis of key
glycolytic enzymes.
3.2.1 Untrained Participants
As mentioned earlier (Sect. 3.1.1.1), Antonio et al. [70]
examined the effects of EAA supplementation during
6 weeks of combined aerobic and resistance training in
sedentary, untrained individuals. Time to exhaustion during
an incremental treadmill test increased more for those indi-
viduals consuming EAA compared with placebo. Unfortu-
nately, oxygen uptake was not measured to verify whether
this improvement reflected increased oxidative potential of
skeletal muscle or was simply a change in running economy
due to training. To examine whether protein supplementa-
tion enhances oxidative capacity, Ferguson-Stegall et al.
[116] examined the effects of a combined carbohydrate and
protein supplement provided as low-fat chocolate milk ver-
sus an energy-matched carbohydrate supplement or placebo
on changes in muscle oxidative enzymes and maximal aer-
obic power ð_
VO2maxÞin recreationally active, untrained
adults. The training program was 4.5 weeks of 5 day-
sweek
-1
cycling exercise that progressed in duration from
30 to 60 minutes and intensity from 75 to 80 % _
VO2max.
Mean changes in _
VO2max expressed in both absolute
(Lmin
-1
) and relative (mLkg
-1
min
-1
) terms were more
than double for milk compared with the improvements pro-
duced by carbohydrate or placebo. However, there were no
differences between groups in muscle oxidative enzyme
activity or markers of muscle mitochondrial biogenesis.
Additional research is clearly warranted to clarify the
potential mechanisms that might account for faster gains in
aerobic power with milk during these initial phases of
endurance training.
3.2.2 Sports-Specific and Military Training
The use of protein supplements on development of aerobic
and anaerobic power during the early training phase of elite
junior judoists was examined by Laskowski and Anto-
siewicz [117]. Both protein and placebo groups increased
aerobic and anaerobic power over an initial 4-week period
of exercise and supplementation but the changes were
greater for those consuming protein. However, after an
additional 3 months of training without supplementation,
_
VO2max was similar between groups.
Because leucine is an independent stimulator of muscle
protein synthesis [56], Crowe et al. [118] studied the
effects of 6 weeks of daily leucine supplementation on
aerobic and anaerobic power of outrigger canoeists who
maintained their normal 8 hoursweek
-1
of training
throughout the study. Peak power during arm-cranking and
rowing time to exhaustion at 75 % _
VO2max increased more
with leucine than placebo. The authors suggested leucine
supplementation enhanced recovery and repair of muscle
damage following training and thereby maximized muscle
adaptations during the 6-week period.
Using a repeated measures crossover design, the effects of
a carbohydrate ?protein supplement provided immediately
following a training session were studied during the indoor
season using national competitive badminton players [119].
Participants consumed carbohydrate ?protein or a low-
calorie carbohydrate supplement throughout 14–15 weeks
of training. Although players reported feeling more alert and
stronger with the carbohydrate ?protein supplement, there
were no differences between supplements on _
VO2max, leg
strength, lean mass or body fatness, grip strength, or 20-m
shuttle-run performance. These data suggest that although
players may report they feel better with ingestion of a car-
bohydrate ?protein recovery supplement, this does not
translate into improvements in physical function.
Protein Supplements and Exercise Performance
123
Walker et al. [120] examined the effects of a whey
protein and leucine supplement on physical performance
for U.S. Air Force personnel conducting their normal
training over a period of 8 weeks, which included a min-
imum of 3 daysweek
-1
of aerobic and muscle endurance
exercise. Before and following each training session par-
ticipants consumed whey protein ?leucine or an isocalo-
ric carbohydrate supplement. Multiple measures of
performance improved with training but there was no dif-
ference between groups. However, since the training pro-
grams were not standardized, the interpretation of these
findings is not straightforward. Further, some of the par-
ticipants reported they were not consuming the supple-
ments every day. This study highlights the problems
associated with attempting to transition the use of protein
supplements to the general population based on studies
conducted with elite athletes. Most members of the general
population do not participate in homogenous training reg-
imens and may not be as motivated as elite athletes to
adhere to strict supplementation schedules.
3.2.3 Summary: Aerobic and Anaerobic Power
A detailed summary of the effects of protein supplements
on aerobic and anaerobic power is provided in Table 3. The
effects of protein supplementation during aerobic training
or during sporting activities that require a combination of
aerobic and anaerobic power for success have not been
definitively established. The limited information available
indicates that when protein supplements are consumed
following training sessions, there are faster gains in _
VO2max
during the first several weeks of aerobic training for pre-
viously untrained individuals [116] or during the beginning
of the training cycle for athletes [117], as well as greater
gains in anaerobic (Table 5) power during normal training
periods for competitors [117,118].
4 Discussion
4.1 General Study Limitations of Papers Reviewed
Examining changes in caloric and macronutrient intake of
the diet throughout the course of a study is critical for
isolating the effects of protein supplementation. The
validity of a study is reduced if total caloric and protein
intake are not adequately reported [89,91,119] or in cases
where changes in diet are not consistent or do not reflect
the additional supplements (i.e., protein or carbohydrate)
provided to different groups of participants [81,104,106,
107,111]. It should also be noted that in the studies
reviewed above, mean normal daily protein intake for
Table 5 A summary of the performance outcomes for the effects of protein and/or carbohydrate supplements on aerobic and anaerobic power
Study Training program Supplementation Performance outcomes
Intensity Frequency Duration
(weeks)
Antonio et al.
[70]
20 min @ 70 % HR
max
39/week 6 12.8 g EAA pre/post-
training ?12.8 g non-training
AM
PRO [PLA for incremental
treadmill time to maximum
Crowe et al.
[118]
Outrigging canoe, cycling,
jogging and resistance
training
8 h/week 6 45 mg/kg/day leucine PRO [PLA for peak arm-
cranking power, TTE at 75 %
rowing _
VO2max
PRO =PLA for BM
Fahlstro
¨m et al.
[119]
Elite badminton club
training
49/week 15 0.62 g/kg CHO ?0.22 g/kg
PRO post-training
CHO ?PRO =PLA for LBM,
leg IKST, _
VO2max
Ferguson-
Stegall et al.
[116]
60 min @ 75–80 % _
VO2max 59/week 4.5 4 mL/kg milk, CHO or PLA at 0
and 1 h post-training
Milk [[CHO =PLA] for
_
VO2max
Milk =CHO =PLA for
oxidative enzymes
Laskowski and
Antosiewicz
[117]
47 % endurance, 35 %
speed and 18 % resistance
training
119/week 4 0.5 g/kg/day PRO after AM
training
PRO [PLA for _
VO2max, peak
power and total work during
30-s Wingate
Walker et al.
[120]
Self-regulated running and
resistance training
C39/
week
8 19.7 g whey ?6.2 g leucine
pre/post-training, 29AM non-
training
PRO =CHO for 3-mile run and
sprint
PRO [CHO for 1 RM bench
press
AM morning, BM body mass, CHO carbohydrate, EAA essential amino acid, HR
max
maximal heart rate, IKST isokinetic strength, LBM lean body
mass, PLA placebo, PRO protein, RM repetition maximum, TTE time to exhaustion, _
VO2max maximal aerobic power
S. M. Pasiakos et al.
123
participants varied considerably, from slightly less than 1
to well over 2 gkg
-1
per day but few studies reported the
nitrogen balance of their participants [72,90,96,112].
Since protein supplements may be more effective when
participants are in an otherwise negative nitrogen balance
due to their normal diet [121,122], the benefits of a diet
that is typically high in protein may offset any further
advantage additional protein supplements might provide. In
these situations, ingestion of the supplement in close
proximity to the beginning or immediately following
exercise may be more critical than the total dose provided
throughout the day [57,73,123]. However, the only study
that was conducted with resistance-trained participants and
included metrics of performance failed to support this
premise [112]. The mean total dose of protein supplement
provided varied considerably among the studies reviewed
from a low of 3 gday
-1
of leucine [118] to over
100 gday
-1
of whey or casein [107]. As little as 6 g EAA
consumed within 1 hour of resistance training is known to
stimulate muscle protein synthesis [64] with maximal
stimulation obtained with 20 g of intact whole-egg protein
ingestion following exercise [65]. Thus, although the pro-
tein dose provided in some studies may not have been
optimal, there were no apparent relationships between the
dose provided and the gains in muscle strength or aerobic
and anaerobic power.
Many studies that were reviewed justified selection of
their sample size with a priori calculations using sample
variances and expected effect sizes from their previous
research and other publications. However, this a priori
justification was not always described [70,7274,77,82,
86,87,8996,101,104,107110,112,117,119].
Studies with small numbers of participants in some or all
of their experimental groups [72,87,91,96,105,107,
112,117,118], which results in low statistical power and
therefore increased risk of a type II error, should be
replicated to verify their findings. In addition, some
authors reported, for various reasons, loss of data due to
withdrawal or exclusion of participants after the study
began [77,85,91,95,96,104,105,107], which may
indicate the need to conduct additional testing to validate
their results.
The reliability, reproducibility, and sensitivity of per-
formance test metrics selected to evaluate changes in per-
formance with protein supplements were also of concern
across the papers reviewed. It is unclear whether the sen-
sitivity analyses conducted by Amann et al. [124] for
cycling time-trial and time-to-exhaustion tests have been
performed for measures of muscle strength using isoki-
netic, isometric or 1 RM techniques. Since many investi-
gations incorporated more than one method to evaluate
changes in muscle strength and reported consistent [71,81,
87] or inconsistent [73,74,89,102,104] findings for the
same or different muscle groups, sensitivity of these vari-
ous test metrics may not be similar. Other factors such as
specificity of adaptation to the training velocity of con-
traction may explain disparate findings reported with slow
versus fast isokinetic tests of muscle strength [74], which
speaks to the advantage of using 1 RM tests for exercises
performed during the training programs to evaluate chan-
ges in muscle strength with supplements [75,76,81,82,
9294,96,102107,111]. In addition, several studies
assessed various functions of muscle performance includ-
ing tests of aerobic and anaerobic power alone [117,118]
or in combination with tests of muscle strength [70,108,
109,112,119,120] and it is unclear whether sensitivity of
these various test metrics are similar.
Likewise, the sensitivity and accuracy of the various
methods used by studies to estimate muscle or lean mass is
noteworthy. The use of magnetic resonance imaging pro-
vides the most accurate estimate of muscle mass [125]but
this methodology is expensive and was usually not used in
the studies reviewed [69,71,73,75]. Dual X-ray absor-
bance technology was consequently used [77,82,85,89,
9294,103109,111,112] but this method can overesti-
mate muscle mass due to its inclusion of organ tissue mass
and body water [125]. Finally, estimates of fat-free mass
were made from measures of body density with hydrostatic
weighing [72,76,81,86,95] and/or from skinfold and limb
circumference measures [72,76,87,90], but these meth-
odologies cannot determine accurate changes in the muscle
mass component.
4.2 Muscle Mass and Strength
A topic of concern across studies that incorporate resis-
tance-training programs is whether protein supplements
would affect performance differently for untrained indi-
viduals versus individuals who are regularly active, or elite
athletes. The well documented occurrence of neural adap-
tation during the early period of resistance training [97,
126,127] raises doubts about whether protein supplements
are themselves beneficial, especially among untrained
individuals. In fact, when the confounding influence of
neural adaptations during the early training period was
removed, no effect of protein supplementation on measures
of muscle strength was observed [71].
Another important unresolved issue is the minimum
duration of training required to induce measurable pheno-
typic changes in muscle and observe benefits of protein
supplementation. Increases in muscle cross-sectional area
have been observed in as few as nine sessions over 3 weeks
of resistance training [128], although it is uncommon to see
measureable changes in less than 6–8 weeks [70,75,81,
96]. Willoughby et al. [76] reported greater gains in lean
mass, strength, myofibrillar contractile protein and myosin
Protein Supplements and Exercise Performance
123
RNA expression with protein supplementation for
untrained volunteers following 10 weeks of alternating
upper and lower body training 4 daysweek
-1
. Others also
reported increases in muscle cross-sectional area deter-
mined from tomography [86] or ultrasound [90], angle of
pennation [90], and proliferation of satellite cells and
myonuclei [91] with training programs of at least 8 weeks
in duration. In addition, even with trained participants,
changes in muscle cross-sectional area and muscle con-
tractile protein that were related to gains in muscle strength
were observed after 8–11 weeks of supplementation that
involved resistance training 3–4 timesweek
-1
[105,106,
109]. These data suggest that a training stimulus of at least
8 weeks in duration with appropriate progressions in
intensity, frequency, and duration is necessary before
measurable changes in phenotype and muscle function
occur and reflect altered rates of protein signaling and
expression. This interpretation is supported by a recent
meta-analysis that concluded protein supplementation
resulted in greater gains in lean mass, muscle cross-sec-
tional area and 1 RM strength for both trained and
untrained participants during training that averaged
12 weeks’ duration and was conducted at least three times
weekly [24].
Typically, the majority of studies reviewed used whole-
body resistance training programs that would be expected
to distribute increases in lean mass throughout the body.
However, measures of strength were typically restricted to
one upper (bench press) and/or lower body (leg press)
exercise. Protein supplementation often led to greater gains
in lean mass with training but these changes were not
associated with similar improvements in metrics of muscle
strength [73,85,89,90,92,93,104,111]. As noted by
Volek et al. [85], restricting the measure of strength to a
specific movement may not be the best way to represent the
functional gains in lean mass distributed throughout the
body. From a research perspective, one way to circumvent
this issue is to use a single-limb resistance-training proto-
col [71,75,87], but the findings from these studies may be
limited by the small muscle mass recruited during training
[71] or carry-over effects to the non-supplemented and/or
untrained limb [75,87].
Another unresolved issue is the optimal composition of
the supplements provided. Several studies examined
effectiveness of the type of protein supplement provided.
These studies noted similar improvements in lean mass
and/or strength with whey and soy [82,85], whey and
casein [108], specifically modified whey and standard
whey [86], or whey and rice [109] supplements, greater
increases with ingestion of whey isolate versus casein
[107], and greater improvements when casein [111]or
BCAA [110] were combined with whey. However, dietary
records were not collected, not reported or changed
throughout training in some of these studies, which may
compromise their validity [107,108,111]. Comparisons
were also made between energy-matched carbohydrate and
carbohydrate ?protein supplements, with protein deliv-
ered as EAA [90], low-fat milk [9294], milk hydrolysate
[91], or yogurt [95], or between energy-matched whey
protein isolate and protein ?carbohydrate [106]. When
the resistance-training stimulus was of sufficient duration
and frequency, addition of protein with carbohydrate in the
form of milk led to greater gains in lean mass and/or
strength in untrained participants than energy-matched
carbohydrate supplementation [93,94], but improvements
in strength and muscle cross-sectional area were no dif-
ferent when protein was provided alone or in combination
with carbohydrate [106]. Collectively these findings dem-
onstrate carbohydrate has little effect on changes in muscle
protein accretion following resistance training lasting sev-
eral weeks, in agreement with results of isotope tracer
studies conducted following a single bout of resistance
exercise [67].
Recently, it has also been shown that differences among
participants in microRNAs involved in post-translational
control of genes coding for skeletal muscle protein growth
are related to the variability observed for changes in lean
mass and muscle strength that follow resistance training
[129]. Thus, despite random allocation prior to the initia-
tion of resistance training, it is still conceivable that some
or all of the differences observed between groups may be a
reflection of those characterized as high or low responders
due to differences in microRNA expression [129] rather
than to any effect related to protein supplementation.
4.3 Aerobic and Anaerobic Power
There are also various unresolved issues with respect to
aerobic and anaerobic power and protein supplements. For
example, the relationships between training, protein sup-
plementation and mitochondrial protein synthesis are not
understood. There is evidence in support of a preferential
stimulus for mitochondrial protein synthesis during the
early stages of aerobic training for untrained individuals
[113], which appears consistent with faster gains in _
VO2max
or treadmill running time to exhaustion that have been
attributed to protein supplementation [70,116]. In addition,
mean increases of 20–50 % in mitochondrial enzyme
activity, such as cytochrome oxidase, have been reported in
as little as 6–10 training sessions [130,131], supporting the
potential for rapid changes in protein synthesis to be aug-
mented with supplementation during early phases of train-
ing. Unfortunately, the only study that compared changes in
mitochondrial enzyme activity failed to demonstrate faster
gains during the initial weeks of training with protein sup-
plementation [116]. Further, as reported by Breen et al.
S. M. Pasiakos et al.
123
[115], preferential effects of protein supplements on rates of
mitochondrial protein synthesis decrease as participants
become more adapted to the training stimulus. Neverthe-
less, greater changes in metrics of aerobic performance such
as _
VO2max, treadmill run time, or rowing time to exhaustion
have been reported following protein supplementation for
several weeks for both untrained [70,116] and trained
participants [117,118]. Clearly, additional research is
warranted to elucidate the mechanism(s) responsible for
improvements in _
VO2max and other metrics of aerobic per-
formance observed following only 4–6 weeks of protein
supplementation.
The mechanisms responsible for faster gains in anaero-
bic power following protein supplementation have also not
been determined. The improvements observed are not
simply related to greater gains in muscle mass since both
peak power and total work, when expressed per unit of
mass, increased following supplementation [117,118]. As
such, further study is required to assess anaerobic-associ-
ated protein signaling and effects of protein supplements
on muscle buffering capacity.
5 Summary Evidence Statements
This paper has reviewed the evidence base that supports
use of protein supplements during or following exercise to
increase the gains in muscle mass and strength, and aerobic
and anaerobic power, which occur as a result of training.
Based on our interpretation of the available evidence base,
we offer the following evidence statements regarding the
use of protein supplements to enhance muscle mass and
strength and/or aerobic and anaerobic power.
5.1 Evidence Statement—Ingestion of Protein
to Increase Muscle Mass and Strength
There is consistent and good quality experimental data that
shows, in untrained individuals, changes in lean mass and
muscle strength observed during the initial weeks of
resistance training are not influenced when protein sup-
plements are provided (evidence category A). There is
limited, but quality experimental data to support the
statement that as the duration and frequency of the resis-
tance training duration is increased for untrained or trained
individuals, ingestion of protein supplements will promote
greater gains in lean mass and muscle strength (evidence
category B). There is consistent and good quality experi-
mental data that show that addition of carbohydrate to
protein supplements will not promote any further changes
in lean mass and muscle strength observed during a resis-
tance training program (evidence category A). There is
limited, but quality experimental data that show that the
type or combinations of various types of protein supple-
ments will affect the gains in lean mass and muscle
strength observed throughout resistance training (evidence
category B).
5.2 Evidence Statement—Ingestion of Protein
to Increase Aerobic or Anaerobic Power
There is limited, but quality experimental data to support
the statement that ingestion of protein supplements fol-
lowing daily training for several weeks will enhance gains
in _
VO2max in previously untrained individuals or athletes at
the beginning of their seasonal training programs or result
in improvements in tests of aerobic and anaerobic power
for athletes during their normal training programs (evi-
dence category B).
6 Future Research
It is hoped this review will provide stimulus for additional
research that links measures of muscle protein synthesis,
and also intracellular signaling following protein supple-
mentation and exercise, to measures of muscle mass and
function. Also, it is suggested that future studies that recruit
untrained individuals should consider including a baseline
resistance training period to accommodate the influence of
neural adaptations on performance metrics similar to the
design of Erskine et al. [71]. In addition, the confounding
effects of an individual’s nitrogen balance before supple-
mentation and variations in dietary protein intake
throughout the period of training and supplementation
should be repeatedly assessed throughout the investigation
and perhaps be considered as a covariate with data analy-
ses. Since experienced resistance-trained individuals rou-
tinely consume high-protein diets, additional research is
needed to address the importance of the timing and type of
protein supplement consumed.
In contrast to the volume of research focused on
understanding the effects of protein supplementation
combined with resistance training on skeletal muscle, there
is limited data that relates protein supplementation with
longitudinal adaptations in aerobic or anaerobic power.
Although there is evidence to support a role for protein
supplements for enhancing adaptation during the early
phases of aerobic and anaerobic training [116118], the
mechanisms have yet to be fully described and additional
research is certainly warranted. Collectively, findings from
these studies would provide the necessary evidence base to
support or refute the use of protein supplements for greater
gains in lean mass that result in improved muscle strength,
and aerobic and anaerobic power.
Protein Supplements and Exercise Performance
123
7 Conclusions
This review has assessed the existing evidence base that
could support use of protein supplements during resistance
training to enhance gains in muscle mass and strength and
during an aerobic- or sport-based training program to
enhance gains in aerobic and anaerobic power. Although
there is overwhelming evidence that supports the rationale
for including protein supplements before or immediately
following a bout of resistance or aerobic exercise to
enhance protein synthesis and anabolic signaling, to date,
these acute changes have not been shown to be consistently
translated into greater long-term gains in muscle mass or
strength and increases in aerobic and anaerobic power.
Nevertheless, additional research is warranted that causally
relates the time course of changes in protein synthesis, and
associated anabolic signaling after exercise, to changes in
muscle mass or strength and gains in aerobic and anaerobic
power that may result from protein supplementation.
Acknowledgments This work was supported by the US Army
Medical Research and Materiel Command (USAMRMC) and the
Department of Defense Center Alliance for Dietary Supplements
Research. The views, opinions and/or findings in this report are those
of the authors, and should not be construed as an official Department
of the Army position, policy or decision, unless so designated by
other official documentation. Citation of commercial organization and
trade names in this report do not constitute an official Department of
the Army endorsement or approval of the products or services of these
organizations.
T.M. McLellan was supported by the Oak Ridge Institute for Sci-
ence and Education through an interagency agreement between the
U.S. Department of Energy and USAMRMC.
The authors have no potential conflicts of interest that are directly
relevant to the content of this review.
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... Due to higher energy expenditure, athletes consume supplements which allow them to sustain the training load [14]. According to our ndings, the most used supplement was whey protein (n = 72; 64.28%), which is used primarily to increase adaptations mediated by resistance exercise, despite the different effects on the body [24]. However, some CFPs may attribute performance improvement to whey protein, despite being used after training sessions to improve muscle recovery [25,26]. ...
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Purpose: We aimed to determine the prevalence of the use of supplements among CFPs. Moreover, we sought to elucidate which factors may be associated with dietary restraint, a dimension of eating behavior that seems to be crucial for food intake, energy availability, fatigue, and performance. Methods CFPs aged 18-64 years (n = 112; 57 male; 55 female) were included in this cross-sectional, exploratory, and descriptive study. They answered an online questionnaire containing questions to assess prevalence, type, and reasons for supplements use, besides information about sociodemographic variables and prevalence of the main chronic morbidities. To analyze aspects of eating behavior, the “Three-factor eating questionnaire (TFEQ) - R21" was used. The Pittsburgh Sleep Quality Index questionnaire (PSQI) was used to assess sleep time and quality. Results: Eighty-seven CFPs (50 male; 37 female) reported currently use of dietary supplements. Whey protein was the most used supplement (n = 70), followed by creatine (n = 54). Eating behavior dimensions of emotional eating, binge eating, and cognitive restraint displayed no differences between genders and CFPs of levels. Conclusion: CFPs seem to be using some supplements with purposes which conflict with those supported by scientific evidence. Regarding eating behavior dimensions, physical exercise may be able to suppress emotional eating, possibly justifying the lack of difference in our results. The use of supplement is prevalent among CF practitioners, but it seems they need nutrition education.
... 2022;57(3):166-178 P rotein and amino acid (protein/aa) supplementations are widely used by recreational weightlifters and competitive athletes along with resistance training to improve muscle strength, endurance, and muscle mass. 1,2 It is often suggested that protein/aa supplements aid to maximize the adaptive response of skeletal muscle to prolonged resistance-type exercise training. 1 Some studies have reported that resistance training may increase the adaptive response of skeletal muscle to protein/aa, 1,3 whereas others reported only small or trivial effects. ...
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The objective of this study was to investigate the effect of protein and/or amino acid supplementation on muscle mass and strength in a healthy population. A structured literature search was conducted from database inception up to October 23, 2019, using PubMed and Scopus. Data were collected from randomized controlled trials and weighted mean difference, and its 95% confidence interval was calculated by using a random-effects model. Risk of bias was assessed using the Cochrane tool. Data were included from 46 randomized controlled trials, totaling 2049 participants. Protein but not amino acid supplementation resulted in significant positive effects on muscle mass (weighted mean difference, 0.47 kg; 95% confidence interval, 0.18-0.75 kg; P < .001) and upper body strength. The significant effect of protein supplementation on muscle mass persisted in the
... The contradictory findings may relate to differences in study duration. In a systematic review by Pasiakos et al. [153], it was reported that the beneficial effects of protein supplementation on changes in lean mass and/or muscle strength were only evident when resistance training programs were 8 weeks' duration or longer. Thus, the 6-week concurrent training and protein supplementation study by Forbes et al. [68] may have been too short to demonstrate a beneficial effect of protein supplementation on increases in upperand/or lower-body muscle strength (i.e., 1-RM bench press and leg press). ...
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Background Engaging in both resistance and endurance exercise within the same training program, termed ‘concurrent exercise training,’ is common practice in many athletic disciplines that require a combination of strength and endurance and is recommended by a number of organizations to improve muscular and cardiovascular health and reduce the risk of chronic metabolic disease. Dietary protein ingestion supports skeletal muscle remodeling after exercise by stimulating the synthesis of muscle proteins and can optimize resistance exercise-training mediated increases in skeletal muscle size and strength; however, the effects of protein supplementation on acute and longer-term adaptive responses to concurrent resistance and endurance exercise are unclear. Objectives The purpose of this systematic review is to evaluate the effects of dietary protein supplementation on acute changes in muscle protein synthesis and longer-term changes in muscle mass, strength, and aerobic capacity in responses to concurrent resistance and endurance exercise in healthy adults. Methods A systematic search was conducted in five databases: Scopus, Embase, Medline, PubMed, and Web of Science. Acute and longer-term controlled trials involving concurrent exercise and protein supplementation in healthy adults (ages 18–65 years) were included in this systematic review. Main outcomes of interest were changes in skeletal muscle protein synthesis rates, muscle mass, muscle strength, and whole-body aerobic capacity (i.e., maximal/peak aerobic capacity [VO2max/peak]). The quality of studies was assessed using the National Institute of Health Quality Assessment for Controlled Intervention Studies. Results Four acute studies including 84 trained young males and ten longer-term studies including 167 trained and 391 untrained participants fulfilled the eligibility criteria. All included acute studies demonstrated that protein ingestion enhanced myofibrillar protein synthesis rates, but not mitochondrial protein synthesis rates during post-exercise recovery after an acute bout of concurrent exercise. Of the included longer-term training studies, five out of nine reported that protein supplementation enhanced concurrent training-mediated increases in muscle mass, while five out of nine studies reported that protein supplementation enhanced concurrent training-mediated increases in muscle strength and/or power. In terms of aerobic adaptations, all six included studies reported no effect of protein supplementation on concurrent training-mediated increases in VO2max/peak. Conclusion Protein ingestion after an acute bout of concurrent exercise further increases myofibrillar, but not mitochondrial, protein synthesis rates during post-exercise recovery. There is some evidence that protein supplementation during longer-term training further enhances concurrent training-mediated increases in skeletal muscle mass and strength/power, but not whole-body aerobic capacity (i.e., VO2max/peak).
... Reasons for these differences are unclear, but rapid neurological adaptation may be prominent in the first 2-3 wk of training (50,51) masking any influence of nutritional intervention on strength gains (2,46). Moreover, functional testing as employed in this study may capture an element of aerobic and/or anaerobic adaptation (52), which was augmented in the short term by provision of exogenous protein (53). Although a mechanism underpinning this adaptation is yet to be established, the apparent cyclical nature of this change in PPB but not PLA (Fig. 3, A and B) suggests a physiological mechanism, which warrants future investigation. ...
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Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. The present study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n=15; age, 24 ± 1 years; BMI, 22.3 ± 0.7 kg·m ⁻² ) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults. Versus isocaloric placebo (PLA; n=14; age, 25 ± 2 years; BMI, 23.9 ± 1.0 kg·m ⁻² ), PPB increased 48 h MyoPS rates after the first RET session measured using deuterated water (2.01 ± 0.15 %·d ⁻¹ vs. 1.51 ± 0.16 , respectively; P<0.05). Additionally, PPB increased isokinetic muscle function over 10 sessions of training relative to the untrained control leg (%U) from 99.9 ± 1.8 pre-training to 107.2 ± 2.4 %U at session 10 (versus 102.6 ± 3.9 to 100.8 ± 2.4 %U at session 10 in PLA; interaction P<0.05). Pre-to-post-training, PPB increased type II fCSA (PLA: 120.8 ± 8.2 to 109.5 ± 8.6 %U; PPB: 92.8 ± 6.2 to 108.4 ± 9.7 %U; interaction P<0.05), but the gain in quadriceps muscle volume was similar between groups. Similarly, PPB did not further increase peak isometric torque, muscle function or MyoPS measured post-training. This suggests that although PPB increases MyoPS and early adaptation, it may not influence longer term adaptations to unilateral RET.
... The MPS rate is higher than the muscle protein breakdown (PMB) rate in the 3 h after the exercise training, the soy protein intake within the 3 h induced a much greater muscle anabolic response [16]. Proper resistance exercise training by supplementation with proteins can help improve muscle strength and quality [17,18]. The mechanism underpinning the effect might be the post-exercise ISPG administration promoting the MPS rate and muscle restoration from the exercise, which due to the energy depletion, caused muscle tissue damage and free radical accumulation. ...
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It is well known that supplementation with high protein after exercise can effectively promote muscle synthesis and repair, while green tea is rich in catechins that have antioxidant effects. We aimed to explore the effects of green tea combined with isolated soy protein on increase muscle mass in resistance-trained mice. A total of 32 male ICR mice (8-weeks old) were divided into four groups (n = 8/group), sedentary control group (SC), isolated soy protein with green tea group (ISPG), resistance training group (RT), isolated soy protein and green tea combine with resistance training group (ISPG + RT). All mice received control or ISPG by oral gavage for four consecutive weeks. Forelimb grip and exhaustive swimming time were used for exercise performance evaluation. In biochemical profile, we analyzed lactate, ammonia, blood urea nitrogen (BUN), and glucose and muscle damage index creatine kinase (CK) after exercise as biochemical parameters of exercise fatigue. The grip strength, muscular endurance, and exhaustive swimming time of the ISPG + RT group were significantly increased than other groups (p < 0.05), and also significantly decreased in serum lactate and ammonia levels (p < 0.05, respectively). The ISP + RT group was not only increased in quadriceps weight, (p < 0.05) but also decreased EFP (p < 0.05). We recommend using a 4-week supplementation with ISPG, combined with RT, to increase muscle mass, exercise performance, glycogen storage, and reduce fatigue biochemical parameters after exercise. The benefits of long-term supplementation or application to human supplementation can be further explored in the future.
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Background & Aims Skeletal muscle losses (both quantitative and qualitative) and the consequent risk of sarcopenia are important issues in people living with HIV (PLWH), even when treated with antiretroviral therapies (ART). We aimed to conduct a systematic review (SR) investigating the effects of dietary interventions with proteins, amino acids, and other nitrogenated compounds on the skeletal muscle of PLWH. Methods We searched the published literature until August 24th, 2020, including clinical trials predominantly with AIDS-free PLWH treated with ART. Results From the 82 studies initially selected, 75 were excluded for the following reasons: nutritional interventions different from nitrogenated compounds; non-nutritional interventions; lack of information on body composition; and studies with most participants with AIDS. From the publications included (n = 7), the majority were performed with small and heterogeneous samples. None of the studies included any new-generation ART or pre- or post-exposition drugs. Two studies found benefits of supplementation on muscle mass; one was performed in a very unfavorable socioeconomic setting, and the supplementation was based on food-derived substances. The other study supplemented creatine, and its benefits were found only when combined with physical exercise training and only by one of the methods of body composition analysis (DXA). Conclusions Our results showed that nutritional interventions with proteins, amino acids, or other nitrogenated compounds could not improve the skeletal muscle mass in PLWH. Further studies are needed, with bigger sample sizes and more precise control of ART schemes. Systematic Review Registration PROSPERO registration number CRD42019139981.
Chapter
The availability of safe food with high quality attributes is essential for crew during their space flights as an adequate and balanced energy and nutrients intake is essential to avoid weight loss and to minimize negative effects on the immune system, physiological functions as well as the metabolic and health status that, in turn, could impair the working and mental performances of the astronauts. Space foods must comply with high safety requirements while keeping qualitative properties and sensory acceptability for storage times matching the long‐terms missions. In general, conventional and intense processes such a scanning, and drying are experienced technologies used for space foods that guarantee high safety levels and long‐storage time. However, several factors contribute to a reduced food intake during space missions including the relatively low food variability, the relative low quality and palatability of the space processed foods, the degradation reactions that develop during the space missions affecting the sensory properties and decrease the nutritional value. In the perspective of long‐time space missions (up to 3 years) innovative technologies, hurdle technology approaches, and new packaging materials represent an interesting alternative for the future space food systems. Recent scientific evidences highlight also the importance to provide space foods with an adequate nutrients bioavailability and bioaccessibility and these aspects s need to be taken into account when designing future space food products. The enrichment of foods with micro‐ and macro‐nutrients as well as of bioactive components (e.g. probiotics, antioxidant compounds) to fulfill the nutritional requirements is an interesting strategy to enhance the nutritional properties and respond to the metabolic needs of the space crew. This chapter will review the current processing technologies applied to produce space food and, based on the current scenarios and scientific knowledge in the field, the perspectives in the design and development of space foods for future missions.
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Isometric strength training has been reported to benefit various sport-related dynamic performances. However, it is still unknown whether performing isometric strength training at single or multiple joint angles would elicit greater benefit. Purpose: To compare the effects of isometric bench press performed at single (SIBP) and multiple (MIBP) joint angles on dynamic strength and overhead throwing performance. Methods: Sixteen male softball and baseball athletes performed overhead throwing, 1-repetition-maximum (1RM) bench press, and ballistic push-up during pretest and posttest. They were then randomly assigned to either SIBP or MIBP to undergo 12 strength training sessions. During the training, isometric bench press was performed at only 90° elbow angle for SIBP but at 60°, 90°, and 120° elbow angles for MIBP. Results: A significant main time effect was observed for bench press 1RM (P = .003) and relative 1RM (P < .001). Similarly, a significant main time effect was observed for ballistic push-up peak power only (P = .037). There was no significant change in overhead throwing velocity in either group. There was also no significant difference in change in all measures between groups. However, a moderate effect in favor of MIBP was observed for change in ballistic push-up peak power (P = .180, g = 0.67). Conclusions: Based on the current findings, the inclusion of both SIBP and MIBP were equally beneficial to maximal strength development. However, performing MIBP had a greater effect on power development.
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1 Finland HÄKKINEN K., KOMI P.V. & TESCH P.A. Effect of ccmbined concentric ard eccentric strength training and detraining on force-time, muscle fiber-and metabolic characteristics of leg extensor muscles. Scand. J ,Sports Sci. 3 (2): 50-58, 1981. Prog¡essive strength training of combined concentric and eccentric contractions were performed three times a week for 16 weeks by 14 males {20-30 yrs of age) accustomed to weight training. The training peeriod was iollowed bv 8 weeks of detraining. The training program consisted mainly of dynamic exeicises for the ieg-extensovs with loads of 80 to 120 of one maximum repetition The training caused significant improvements in-maximal force (p < 0.001) and various force-time (p (0.05-4.01) para¡àeters. Du¡ing thg I'ast trarning àionìh tbe inãrease in force was gireatly tri¡nited' and there was ¿ decrease in th,e force-time parameters. The marked improvements in mwcle strength were accompanied by ccnsiderable intemål qdaptatioos ,Ín-ttre tnaCned muscle, as Judged from l¡rcreases (p < 0-001) ,iqr. the fibet ãeas ôt tËe Ïast fi¡¡itch (FT) and slow twitch (ST) fibers. Durlng early conditioning improvement i! the qqgs! jump w,as related to tl.e relãtive hypertrop]ty of tr1l ii¡eis fo <0.01). No sier¡j-Êi,cå,r¡t ct¡anges ,in tJre er¡zyme aittv¡tiês oi mÍoki¡¡ase-a¡¡d creatine kirmse were found as a result of-tra¡rrir}g, but i,ndividt¡al charrges in my-o-kinase activity $/ere related to the relative. hypertrop'hy of FT fibers-(p ç 0.05) and Improvernent i+ the squat jump (p < O.Of)-during early conditiontuag. All the ada,p-iatlo:ns'-incilcating musõle hypertrophy occurred. prtm@lv during the last two training mo¡rths. Decreases (p (0.001) in maxirnal force during the detrairring were accompâ-nied bv a sisrificår¡t rediuction in the fi¡b,er areas of ttle fC tp < 0.01) and ST (p < 0.05) tvpes end by a change in bödy-antliropometry.-A periodiè-and partial usage. of àccentr-ic contráctions,-together with conèentric training' is suggested to be effectiùe in training for-maximal force and äso for force-time eharacteristics. In training of longer durations the specific effects of strength trainlng are-obviot¡s and explaiñable by adaptatlons in the trained muscle. Keg tenns: erìzJûne actlvities, muscle mechanics, muscle metabollsn, muscle streng:th.