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Whey Protein Supplementation During Resistance
Training Augments Lean Body Mass
Jeff S. Volek PhD, RD
a
, Brittanie M. Volk MA, RD
a
, Ana L. Gómez PhD
a
, Laura J. Kunces
MS, RD
a
, Brian R. Kupchak PhD
a
, Daniel J. Freidenreich MA
a
, Juan C. Aristizabal PhD
a
,
Catherine Saenz MA
a
, Courtenay Dunn-Lewis MA
a
, Kevin D. Ballard PhD
a
, Erin E. Quann
PhD, RD
a
, Diana L. Kawiecki MA
a
, Shawn D. Flanagan MA, MHA
a
, Brett A. Comstock MA
a
, Maren S. Fragala PhD
a
, Jacob E. Earp PhD
a
, Maria L. Fernandez PhD
b
, Richard S. Bruno
PhD, RD
b
, Adam S. Ptolemy PhD
c
, Mark D. Kellogg PhD
c
, Carl M. Maresh PhD
a
& William
J. Kraemer PhD
a
a
The Human Performance Laboratory, Department of Kinesiology , University of
Connecticut , Storrs , CT
b
Nutritional Sciences Department , University of Connecticut , Storrs , CT
c
Department of Laboratory Medicine , Boston Children's Hospital , Boston , Massachusetts
Published online: 19 Jun 2013.
To cite this article: Jeff S. Volek PhD, RD , Brittanie M. Volk MA, RD , Ana L. Gómez PhD , Laura J. Kunces MS, RD , Brian R.
Kupchak PhD , Daniel J. Freidenreich MA , Juan C. Aristizabal PhD , Catherine Saenz MA , Courtenay Dunn-Lewis MA , Kevin
D. Ballard PhD , Erin E. Quann PhD, RD , Diana L. Kawiecki MA , Shawn D. Flanagan MA, MHA , Brett A. Comstock MA , Maren
S. Fragala PhD , Jacob E. Earp PhD , Maria L. Fernandez PhD , Richard S. Bruno PhD, RD , Adam S. Ptolemy PhD , Mark D.
Kellogg PhD , Carl M. Maresh PhD & William J. Kraemer PhD (2013) Whey Protein Supplementation During Resistance Training
Augments Lean Body Mass, Journal of the American College of Nutrition, 32:2, 122-135, DOI: 10.1080/07315724.2013.793580
To link to this article: http://dx.doi.org/10.1080/07315724.2013.793580
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Original Research
Whey Protein Supplementation During Resistance
Training Augments Lean Body Mass
Jeff S. Volek, PhD, RD, Brittanie M. Volk, MA, RD, Ana L. G
´
omez, PhD, Laura J. Kunces, MS, RD, Brian R. Kupchak, PhD,
Daniel J. Freidenreich, MA, Juan C. Aristizabal, PhD, Catherine Saenz, MA, Courtenay Dunn-Lewis, MA,
Kevin D. Ballard, PhD, Erin E. Quann, PhD, RD, Diana L. Kawiecki, MA, Shawn D. Flanagan, MA, MHA,
Brett A. Comstock, MA, Maren S. Fragala, PhD, Jacob E. Earp, PhD, Maria L. Fernandez, PhD, Richard S. Bruno, PhD, RD,
Adam S. Ptolemy, PhD, Mark D. Kellogg, PhD, Carl M. Maresh, PhD, William J. Kraemer, PhD
The Human Performance Laboratory, Department of Kinesiology (J.S.V., B.M.V., A.L.G., L.J.K., B.R.K., D.J.F., J.C.A., C.S., C.D.-L.,
K.D.B., E.E.Q., D.L.K., S.D.F., B.A.C., M.S.F., J.E.E., C.M.M., W.J.K.), and Nutritional Sciences Department (M.L.F., R.S.B.),
University of Connecticut, Storrs, Connecticut; Department of Laboratory Medicine, Boston Children’s Hospital, Boston,
Massachusetts (A.S.P., M.D.K.)
Key words: whey, soy, protein, resistance training, lean body mass, body composition, amino acids, leucine
Compared to soy, whey protein is higher in leucine, absorbed quicker and results in a more pronounced
increase in muscle protein synthesis.
Objective: To determine whether supplementation with whey promotes greater increases in muscle mass
compared to soy or carbohydrate, we randomized non-resistance-trained men and women into groups who
consumed daily isocaloric supplements containing carbohydrate (carb; n = 22), whey protein (whey; n = 19), or
soy protein (soy; n = 22).
Methods: All subjects completed a supervised, whole-body periodized resistance training program consisting
of 96 workouts (∼9 months). Body composition was determined at b aseline and after 3, 6, and 9 months. Plasma
amino acid responses to resistance exercise followed by supplement ingestion were determined at baseline and 9
months.
Results: Daily protein intake (including the supplement) for carb, whey, and soy was 1.1, 1.4, and 1.4 g·kg
body mass
−1
, respectively. Lean body mass gains were significantly (p < 0.05) greater in whey (3.3 ± 1.5 kg)
than carb (2.3 ± 1.7 kg) and soy (1.8 ± 1.6 kg). Fat mass decreased slightly but there were no differences
between groups. Fasting concentrations of leucine were significantly elevated (20%) and postexercise plasma
leucine increased more than 2-fold in whey. Fasting leucine concentrations were positively correlated with lean
body mass responses.
Conclusions: Despite consuming similar calories and protein during resistance training, daily supplementation
with whey was more effective than soy protein or isocaloric carbohydrate control treatment conditions in promoting
gains in lean body mass. These results highlight the importance of protein quality as an important determinant of
lean body mass responses to resistance training.
INTRODUCTION
Optimizing recovery after exercise is important for eliciting
maximal training adaptations. A large body of literature exists
on the role of protein and carbohydrate ingestion on measures
of protein balance after resistance exercise [1]. Compared to
the fasting state, a bout of resistance exercise has a positive
impact on muscle protein synthesis, but in the absence of dietary
protein intake, net protein balance remains negative [2], even if
carbohydrate is ingested [3]. Moreover, there is now mounting
Address correspondence to: Jeff S. Volek, PhD, RD, Associate Professor, Department of Kinesiology, 2095 Hillside Road, Unit 1110, University of Connecticut, Storrs, CT
06269-1110. E-mail: jeff.volek@uconn.edu
evidence for distinct qualitative effects of protein sources on
muscle anabolism [4–6].
Whey is distinguished from other protein sources due to
its rapid digestion and high content of essential amino acids
(EAAs), which are requisite for stimulating skeletal muscle pro-
tein synthesis [7]. Compared to soy protein, whey has 50% more
branched-chain amino acids (BCAAs) leucine, isoleucine, and
valine. BCAAs are essential amino acids that promote mus-
cle protein synthesis and prevent muscle protein breakdown
[8, 9], and they may offer protection from exercise-induced
Journal of the American College of Nutrition, Vol. 32, No. 2, 122–135 (2013)
C
American College of Nutrition
Published by Taylor & Francis Group, LLC
122
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Resistance Training and Protein Supplementation
muscle soreness [10]. Whey is a rich source of leucine (>10%)
that can directly activate contractile muscle protein synthesis
alone through the mammalian target of the rapamycin (mTOR)
signaling pathway [11]. Compared to soy, whey protein after
resistance exercise results in greater concentrations of leucine
in the blood and specific phosphorylation of mTOR and S6K1,
demonstrating greater activation of molecular signaling related
to protein synthesis [12]. In humans, ingestion of whey protein
at rest [4, 5] or after resistance exercise [13, 14] stimulates mus-
cle protein synthesis. In a direct comparison of protein sources
consumed after a bout of resistance exercise, rates of muscle pro-
tein synthesis over a 3-hour postexercise period were ∼2-fold
higher after whey than casein, whereas soy was intermediate in
between whey and casein [6]. Leucine values in the blood over
the 3-hour period were 73% greater than soy values and 200%
greater than casein values [6].
Acute increases in mTOR signaling and skeletal muscle pro-
tein synthesis should logically translate into chronic increases
in lean body mass, yet few studies have rigorously tested this
hypothesis. There is evidence that supplementation with whey
protein alone [15] or a combination of whey and casein [16, 17]
is more effective than a carbohydrate supplement at augmenting
lean body mass responses to resistance training. In comparison
to casein, ingestion of whey protein during resistance training
has been shown to promote greater increases in lean body mass
and reductions in body fat [18]. On the other hand, a recent
study showed no difference between whey and soy protein with
regard to lean body mass adaptations to resistance training, but
the very short intervention (6 weeks) was likely too short to ob-
serve subtle differences in the anabolic potential of these 2 pro-
tein sources [19]. To our knowledge, no studies have compared
protein sources (whey vs soy) with regard to lean body mass
responses to chronic resistance training longer than 6 months.
In this article, we report lean body mass, body composition,
and amino acid responses to 9 months of resistance training in
a group of healthy men and women randomly assigned to sup-
plement with whey protein, soy protein, or carbohydrate. We
hypothesized that with whole-body resistance training, whey
protein supplementation would enhance leucine availability and
gains in lean body mass.
MATERIALS AND METHODS
Experimental Approach
A prospective parallel 3-group study design was used to com-
pare the effects of nutritional supplementation on body compo-
sition to resistance training. Healthy men and women were ran-
domly assigned in a double-blind manner to supplement daily
with whey protein (whey), soy protein (soy), or carbohydrate
(carb). All subjects performed supervised resistance training.
Body mass, body composition, and maximal strength were de-
termined at baseline and after 32 (∼3 months), 64 (∼6 months),
and96(∼9 months) workouts. An acute resistance exercise test
followed by supplementation with whey, soy, or carbohydrate
was performed at baseline and at 9 months to determine plasma
amino acid response patterns.
Subject Recruitment and Retention
Subjects were men and women aged 18–35 years and not
participating in a systematic, high-intensity resistance program
within 1 year prior to enrollment. Subjects were permitted to
participate in recreational sports or other activities but were
not allowed to participate in outside intense training to avoid
incompatibility with respect to muscular adaptations. Women
were normally menstruating (cycle lengths 28–32 days). Exclu-
sion criteria included the following: hypertension (systolic blood
pressure [SBP] > 150 or diastolic blood pressure [DBP] > 95
mmHg), diabetes, use of tobacco products, use of cholesterol-
lowering and blood pressure medications, change in body weight
> 3 kg during the past 3 months, use of anti-inflammatory med-
ication (aspirin, NSAIDs), alcohol consumption > 3 drinks/day
or 21/week, pregnancy or intention to become pregnant or ab-
normal menstrual phase, initiation or change in hormonal birth
control within last 3 months, allergy to whey or soy, and mus-
culoskeletal injuries or physical limitations affecting ability to
exercise.
More than 1200 subjects responded to recruitment efforts
from March 2008 to January 2011 (see Fig. 1). Many individ-
uals either failed to follow up or did not meet basic inclusion
criteria. A total of 335 participants completed screening forms at
an informational session and 169 subjects started baseline test-
ing. Subjects who completed all baseline tests (n = 147) were
matched according to sex, body mass, and body fat and then
randomly assigned to the whey, soy, or carb group to ensure
equal distribution of men and women of similar body composi-
tion in each group. Subjects were informed of the purpose and
possible risks of the investigation prior to signing an informed
consent document approved by the university’s institutional re-
view board.
Dietary Protocol
Subjects were free living but were provided specific and reg-
ular dietary counseling by registered dietitians that focused on
consuming adequate energy to prevent major loss or gain in
body mass. There was a major emphasis on ensuring a stan-
dard protein intake of 1.0 to 1.2 g ·kg body mass
−1
(not includ-
ing supplementation), which is 25% to 50% above the recom-
mended dietary allowance (RDA) but not so high to potentially
confound subtle differences between protein sources. For the
whey and soy groups, the addition of the daily protein supple-
ment (∼22 g·day
−1
) increased protein intake to ∼1.4 g·kg
−1
.
Energy needs for body mass maintenance were determined by
resting metabolic rate testing using a Parvomedics TrueOne 2400
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION 123
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Resistance Training and Protein Supplementation
Fig. 1. Study flow diagram.
metabolic cart (Sandy, UT) with adjustments for activity. To as-
sist in monitoring energy and protein intake, all subjects were
provided with a handheld personal digital assistant loaded with
a customized dietary program (Edward A. Greenwood, Inc.,
Brookline, MA). Subjects entered daily food and beverage con-
sumption including amounts, time of day, and brands (when
available) for 5 days every 6 weeks. The 5-day diet records were
reviewed and goals were reinforced during one-on-one sessions
with registered dietitians. A subject’s food and beverage selec-
tions, with a focus on protein content of foods, were carefully
reviewed by the dietitian during the counseling session for ac-
curacy prior to transferring the information to a dedicated lab-
oratory computer for analysis. Subjects were weighed weekly
on a calibrated digital scale (Defender 5000, Ohaus, Florham
Park, NJ). Subjects showing a trend for excessive weight gain or
loss ( ± 2.5 kg over baseline weight) were flagged and discussed
by the nutrition team at weekly meetings and provided specific
guidance to adjust caloric and/or protein intakes. Dietary data
were collapsed and reported as mean nutrient intakes at baseline
and 3, 6, and 9 months.
Supplement Protocol
Using a double-blind protocol, the carbohydrate, whey, and
soy powdered supplements were provided in identical individu-
alized packets. They were isocaloric and isonitrogenous (whey
and soy). Nutrient composition based on analysis of 5 packets
each of carbohydrate (maltodextrin), whey protein concentrate,
and soy isolate (isoflavone free) supplements by an indepen-
dent laboratory (Medallion Labs, Minneapolis, MN) is shown in
Table 1. Packets were given to subjects with instructions to mix
the contents in 240 mL of water. Subjects were provided a 2-
week supply with instructions to consume the supplement in the
morning with breakfast on nontraining days and immediately af-
ter exercise on training days. Compliance was assured by having
subjects ingest supplements in the presence of study personnel
on training days. Subjects also recorded the date and time of sup-
plement ingestion on log sheets. Empty packets were returned
and counted at the end of each 2-week period. In addition, all
supplements were spiked with 200 mg of para-aminobenzoic
acid (PABA). Unannounced urine samples were collected from
each subject during a training session approximately one time
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Resistance Training and Protein Supplementation
Table 1. Nutritional Composition of Supplements
a
Carbohydrate Whey Soy
Energy (kcal) 191 194 189
Carbohydrate (g) 45.2 22.5 24.5
Protein (g) 0.8 21.6 20.0
Fat (g) 0.8 1.9 1.3
Saturated fat (g) 0.3 1.0 0.4
Calcium (mg) 201 189 214
Iron (mg) 2.1 2.0 4.4
Phosphorus (mg) 44 114 213
Sodium (mg) 154 183 402
Magnesium (mg) 18 28 28
Potassium (mg) 55 164 78
Amino acid composition (mg)
Alanine — 1050 726
Arginine — 667 1329
Aspartic acid — 2029 1835
Glutamic acid — 3519 3262
Glycine — 409 674
Histidine — 405 447
Isoleucine — 1174 770
Leucine — 2211 1372
Lysine — 1918 1097
Phenylalanine — 703 904
Proline — 1181 810
Serine — 1126 856
Threonine — 1442 671
Tyrosine — 652 651
Valine — 1140 794
a
Values are per serving (packet). Subjects consumed one packet per day.
per month for analysis of the presence of this marker in the
urine. Urine (∼1 mL) was aliquoted into a storage tube, imme-
diately frozen with liquid nitrogen, and stored at −80
◦
C until
analyzed for PABA using a colorimetric method described by
Yamato and Kinoshita [20] with modifications. The intra-assay
coefficient of variation was 7.9%. If PABA concentrations were
2.5-fold higher than baseline or >30 ug·ml
−1
, this indicated that
the subject was compliant with supplement ingestion on that
day. Based on PABA, compliance with the supplement protocol
was 82%.
Resistance Training Program
The whole-body resistance training program consisted of a
flexible, progressive, nonlinear, periodized program character-
ized by within-week variation of the acute program variables as
described by Kraemer and Fleck [21]. Unique to this study is
that we wanted no workout to just be “going through the mo-
tions” and thus the terms flexible and nonlinear. If, for example,
a subject could not perform the weight or repetitions needed
for a “heavy” workout, the trainer then defaulted to one of the
other workouts, typically a light workout. But throughout the
weekly cycle, each subject had the same exposure to the same
workouts, just not on the same day of the week. The resistance
training program was designed to develop whole-body muscula-
ture and was implemented symmetrical to each joint, upper and
lower body, and anterior and posterior body development. Four
styles of workout were utilized: light (12–15 repetitions, short
rest period of 60–90 seconds, lighter intensity); medium (8–
10 repetitions, moderate intensity); heavy (3–6 repetitions, long
rest periods of 2–3 minutes, high intensity); and power (whole-
body exercises using 30%–45% of the estimated 1 repetition
maximum [RM], 3-minute rest periods) for the major muscle
group exercises as well as assistance exercises. Exercises used
included squats (Smith Machine, Life Fitness, Schiller Park,
IL; and free bar), hang cleans, bench presses, bicep curls, calf
exercises, abdominal exercises, lat pull downs, lunges, upright
rows, push presses, and weight plate lifts. Multiple sets (3–5) of
each resistance exercise were performed. The program utilized
free-weight (barbell and dumbbell), machine, and body weight
exercises and limited use of plyometrics (i.e., vertical and hori-
zontal medicine ball throws). Supervised training sessions took
place in the weight room at the University of Connecticut with
a goal of 1 trainer for every 2–3 subjects. Morning, noon, and
evening training sessions were offered throughout the week to
accommodate varying subject schedules and availability. The
duration of sessions varied from 30 to 75 minutes depending on
the type of workout performed. The program was divided into
three 12-week mesocycles and continued until subjects accrued
96 workouts (∼9 months).
We used a designated contact person system whereby sub-
jects were assigned to a member of the training staff after
completing baseline testing. This person’s responsibility was to
schedule subjects for weekly training sessions, hold the subjects
accountable for completing the scheduled sessions, and com-
municate any changes in the training schedule (i.e., inclement
weather cancellation). Training sessions were offered through-
out breaks from the school year. If short-term vacations or con-
flicts occurred during this time, subjects were given the sequence
of workouts and trained on their own, which was validated by
the supervising trainer.
The nonlinear periodization program had built-in accommo-
dations that made it well suited for research in college-aged
individuals. Weekly training schedules were randomized to pre-
vent boredom. We used a flexible nonlinear program with the
workouts optimized for each type of loading. If trainees did not
reach workout loading goals (RM ranges), a replacement work-
out in the sequence was used and that workout was performed
later in the training sequence. For example, if a subject was not
able to perform a heavy workout with high quality within the
first exercise sets, the trainer defaulted to a rest day or light day
that a subject could complete with higher quality. This allowed
for only high-quality workouts to be performed in each ses-
sion. The use of flexible nonlinear resistance training uniquely
allowed for optimal training and accommodation for sickness,
injury, and normal fluctuations in performance capability that
inevitably occurs over long periods of time. Yet the goals for
each week were maintained with no differences in the workout
stimuli between groups.
JOURNAL OF THE AMERICAN COLLEGE OF NUTRITION 125
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Resistance Training and Protein Supplementation
Testing Protocol
Prior to any testing, subjects were familiarized with the
proper technique and sequence of all tests to be performed dur-
ing the actual performance test visit. Height was determined
in triplicate and averaged using a stadiometer (Seca, Hamburg,
Germany). Body mass was measured to the nearest 0.1 kg using
a calibrated digital scale. Body composition was assessed us-
ing dual-energy x-ray absorptiometry (Lunar Prodigy, Madison,
WI). Performance testing consisted of 1 RM squat and bench
press performed on a Smith Machine using proper technique
and the same starting positions each time. Upon arrival, sub-
jects performed a dynamic warm-up consisting of 5 minutes
of cycle ergometer exercise followed by a series of dynamic
stretches. Two warm-up sets of the specific exercise were com-
pleted at 50% estimated 1 RM (8–10 repetitions) and 80% esti-
mated 1 RM (2–5 repetitions). For the squat, the parallel depth
defined as the 90-degree relationship between the femur and
the lower leg (i.e., knee at 90 degrees) f or each subject was
set with a plum line that the bottom of the thigh had to reach
with each repetition in order to be counted as correct technique.
Full range of motion was required for both the bench press and
squat exercises. The testing protocol consisted of 3–5 attempts
with the highest mass lifted with proper form recorded as the
1RM.
On a separate day, at baseline and at 9 months only, an
acute heavy resistance exercise test was performed to determine
plasma amino responses to exercise. Subjects arrived at the lab-
oratory following a 12-hour overnight fast and refraining from
alcohol, caffeine, over-the-counter medications, and exercise for
24 hour. Upon arrival, hydration was confirmed by urine specific
gravity (USG) with a handheld refractometer (model TS400,
Reichert, Lincoln, IL). If USG >1.025, the subject drank wa-
ter before retesting 30 minutes later. Thus, all subjects were
hydrated prior to any testing protocol. An indwelling Teflon
cannula was inserted into a superficial antecubital forearm vein.
After resting quietly in the seated position for 10 minutes, a pre-
exercise blood sample was obtained. Subjects then performed a
dynamic warm-up followed by 6 sets of 10 repetitions of squat
exercise on a Smith Machine with a 2-minute rest between sets.
The load for the first set was set at 60% 1 RM and was s ub-
sequently adjusted based on volitional fatigue to attain a 10
RM on each set. Again, repetitions were counted as complete
only if the participants reached a parallel position defined as
the 90-degree relationship between the femur and the lower leg
(i.e., knee at 90 degrees), which was again verified by a plum
line that marked the individual’s parallel position at the bottom
of the squat. Upon completion of the sixth set, subjects con-
sumed a full serving of the supplement corresponding to their
group assignment. Additional blood samples were obtained at
15, 30, and 60 minutes postexercise while subjects remained
in the seated position. Whole blood was collected into sodium
heparin tubes, centrifuged (1500 × g for 15 minutes at 4
◦
C),
and promptly aliquoted into tubes and stored frozen at −80
◦
C.
Frozen samples were thawed only once before analysis.
Plasma Amino Acid Analyses
Frozen heparinized plasma was thawed at room tempera-
ture and centrifuged at 10,000 × g for 5 minutes to remove
any particulate matter from the fluid. A 25-μL aliquot of the
supernatant was diluted 4-fold with a 1.25 μM internal stan-
dard solution of 3,5-diiodotyrosine. The resultant mixture was
then transferred to a 3 kDa molecular-weight cutoff filter (Pall
Corporation, Port Washington, NY) and centrifuged for 10 min-
utes at 7500 g. The low-molecular-weight filtrate was then di-
luted 12.5-fold in the appropriate mobile phase and used for
amino acid analysis. Amino acids were quantitated by ultra-
performance liquid chromatography–tandem mass spectrome-
try (UPLC-MS/MS) using an Acquity Ultra-Performance LC
system (Waters, Milford, MA) coupled to a Waters Micro-
mass Quattro Premier triple quadrupole instrument (Waters).
The UPLC-MS/MS experimental parameters for this study were
based on the instrument manufacturer’s application notes and
published LC-MS/MS methodologies [22–24] for underivatized
amino acid analysis. Separation was achieved using an LC C18
bridged-ethyl hybrid column (1.7 μm particles × 2.1 × 50 mm,
Waters) with mobile phases of 0.1% (w/v) pentadecafluorooc-
tanoic acid and 0.1% (v/v) formic acid in water/acetonitrile (v/v)
solvent mixtures of 95.5%/0.5% (phase A) and 10%/90% (phase
B) respectively. The sample components were eluted by increas-
ing the percentage of solvent B to 2%, 5%, 20%, 40%, and 100%
at 0.5, 0.8, 2, 4, and 4.5 minutes, respectively. The column was
then equilibrated to 0% phase B over 2.5 minutes where it was
held for an additional 6 minutes to recondition the column. All
data acquisition and processing were performed using MassLynx
4.1 and QuanLynx software (Waters).
Statistical Analyses
Assuming 80% power at an α-level of 5%, we calculated
that 17 participants were required to determine a 0.5 kg dif-
ference in lean body mass between groups (nQuery Advisor,
Statistical Solutions, Saugus, MA). Because this was a biolog-
ical efficacy study, only subjects who completed the required
training sessions and were compliant with the supplement pro-
tocol (>90%) were analyzed. Means and standard measures
of variation were calculated for outcome data, and distribu-
tions were examined for approximate normality and logarith-
mically adjusted if necessary as all data sets met the assump-
tions for linear statistics before analysis. Amino acid responses
to exercise were summarized by area under the curve using the
trapezoidal method. A linear model using a 3-way mixed fac-
torial analysis of variance (ANOVA; i.e., (Carb, Whey, Soy)
× Time); i.e., baseline 3, 6, 9 months) was used to analyze
these data. To determine differences among groups at baseline
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Resistance Training and Protein Supplementation
Table 2. Subject Characteristics
a
Carbohydrate Whey Soy
n (M/F) 13/9 13/6 11/11
Age (years) 22.3 ± 3.1 22.8 ± 3.7 24.0 ± 2.9
Height (cm) 172.0 ± 8.7 171.8 ± 10.3 170.5 ± 2.9
Body mass (kg) 72.4 ± 14.9 74.1 ± 15.7 72.0 ± 8.4
Fat mass (kg) 19.5 ± 9.0 19.4 ± 11.3 20.5 ± 11.3
Lean body mass (kg) 49.8 ± 9.8 51.7 ± 10.7 48.5 ± 10.0
Body fat (%) 26.4 ± 8.7 25.3 ± 12.0 27.3 ± 11.0
Squat 1 RM (kg) 71 ± 583± 660± 5
Bench press 1 RM (kg) 45 ± 552± 545± 5
M = male; F = female; RM = repetition maximum.
a
Values are mean ± SD. No significant differences between groups.
and changes over specific intervals, a one-way ANOVA was
used. When main effects were significant, Bonferroni correc-
tions (or least significant difference [LSD] equivalent to a no
type I error rate adjustment) were made for corresponding pair-
wise comparisons. Performance testing exhibited an ICCR of
p ≥ 0.95. Significance was set at p ≤ 0.05.
RESULTS
There were no significant differences between groups in
physical characteristics at baseline (see Table 2).
There were no significant differences between groups at base-
line in dietary intake (see Table 3). Energy intake remained con-
stant over the intervention in all groups. We also met our goal
of achieving an average protein intake between 1.0 and 1.2 g/kg
body mass (not including supplements). As planned, the main
dietary change was a significant increase in protein intake in the
whey and soy groups and an increase in carbohydrate in the carb
treatment group. Subjects in the whey and soy groups consumed
∼20 g · day
−1
more protein than those in the carb group, cor-
responding to ∼1.4 and 1.1 g · kg body mass
−1
, respectively.
Dietary fat was constant across groups and time, representing
about 25%–30% of total energy.
Body mass and lean body mass significantly increased at 3
months and remained significantly higher than baseline at 6 and
9 months for all groups (see Table 4). The increase in body mass
was not different between groups, but gains in lean body mass
were significantly greater in the whey group at all testing points,
whereas there were no differences between the carb and soy
groups. After 9 months of training, all but 2 subjects in the whey
group showed greater increases in lean body mass than the mean
response for the soy group (see Fig. 2). The same pattern of a
greater increase in lean body mass in the whey group was evident
when looking at only men (carb = 2.6 ± 1.0, whey = 3.6 ±
1.6, soy = 2.6 ± 1.4 kg) or women (carb = 1.9 ± 1.0, whey =
2.8 ± 1.2, soy = 1.1 ± 1.6 kg). There were no significant
main time or group effects for fat mass. There was a main effect
Table 3. Daily Dietary Nutrient Intake
a
Baseline 3 Months 6 Months 9 Months ANOVA
Energy (kcal)
Carb 1892 ± 115 1992 ± 80 2019 ± 66 2003 ± 76 T: p = 0.701
Whey 2111 ± 121 2116 ± 84 2129 ± 69 2083 ± 80 G: p = 0.434
Soy 2032 ± 112 2061 ± 78 1967 ± 64 2104 ± 74 G × T: p = 0.552
Protein (g)
Carb 82.6 ± 6.0 77.2 ± 3.7 77.7 ± 3.4 76.6 ± 3.5 T: p = 0.072
Whey 92.5 ± 6.3 101.3 ± 3.9
∗
99.3 ± 3.6
∗
102.8 ± 3.7
∗
G: p = 0.000
Soy 86.2 ± 5.8 99.1 ± 3.6
∗
94.5 ± 3.3
∗
97.3 ± 3.4
∗
G × T: p = 0.014
Protein (g/kg body mass)
Carb 1.14 ± 0.28 1.08 ± 0.12 1.08 ± 0.10 1.06 ± 0.13 T: p = 0.272
Whey 1.27 ± 0.41 1.38 ± 0.14 1.35 ± 0.22 1.39 ± 0.18 G: p = 0.000
Soy 1.27 ± 0.45 1.41 ± 0.23 1.32 ± 0.14 1.35 ± 0.13 G × T: p = 0.109
Carbohydrate (g)
Carb 238 ± 15 270 ± 12 276 ± 13 275 ± 14 T: p = 0.002
Whey 275 ± 16 288 ± 12 303 ± 13 285 ± 15 G: p = 0.314
Soy 274 ± 15 278 ± 11 275 ± 12 307 ± 14 G × T: p = 0.074
Fat (g)
Carb 62.2 ± 5.7 66.3 ± 3.9 69.2 ± 3.6 67.5 ± 3.9 T: p = 0.108
Whey 72.3 ± 6.0 65.3 ±
4.1 64.3 ± 3.8 62.5 ± 4.1 G: p = 0.420
Soy 66.7 ± 5.6 62.4 ± 3.8 57.4 ± 3.5 58.1 ± 3.8 G × T: p = 0.345
Cholesterol (mg)
Carb 259 ± 33 234 ± 26 228 ± 24 294 ± 29 T: p = 0.218
Whey 253 ± 35 227 ± 28 217 ± 25 239 ± 31 G: p = 0.424
Soy 226 ± 32 208 ± 26 212 ± 24 207 ± 29 G × T: p = 0.682
ANOVA = analysis of variance; G = main group effect; T = main time effect; G × T = Group × Time effect.
a
Values are mean ± SD. Baseline nutrient intake was obtained from a 5-day diet record and each remaining time point (3, 6, 9 months) reflects the average of two 5-day diet
records for each person. Data analyzed by 3 × 4 ANOVA.
∗
p < 0.05 from corresponding baseline value.
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Table 4. Change in Body Composition Responses to Resistance Training
a
3 Months 6 Months 9 Months p-Value (between groups)
Body mass (kg)
Carb 2.2 ± 2.2 2.4 ± 1.9 1.8 ± 2.4 3 months = 0.083
Whey 2.8 ± 2.1 3.3 ± 2.7 3.1 ± 3.0 6 months = 0.444
Soy 1.4 ± 1.8 2.4 ± 3.1 2.2 ± 4.0 9 months = 0.448
Fat mass (kg)
Carb −0.2 ± 1.8 −0.2 ± 1.9 −0.5 ± 2.2 3 months = 0.311
Whey −0.1 ± 1.5 −0.4 ± 2.4 −0.6 ± 2.7 6 months = 0.971
Soy −0.7 ± 1.7 −0.2 ± 2.7 0.2 ± 4.1 9 months = 0.634
Lean body mass (kg)
Carb 2.4 ± 1.4 2.6 ± 1.4 2.3 ± 1.7 3 months = 0.030
Whey 3.1 ± 1.5
∗
3.5 ± 1.3
∗
3.3 ± 1.5
∗
6 months = 0.056
Soy 1.9 ± 1.1 2.4 ± 1.7 1.8 ± 1.6 9 months = 0.016
Percentage body fat
Carb −0.9 ± 1.9 −1.0 ± 2.1 −1.2 ± 2.5 3 months = 0.367
Whey −1.1 ± 1.4 −1.6 ± 2.4 −1.5 ± 2.6 6 months = 0.856
Soy −1.5 ± 1.8 −1.4 ± 2.4 −0.6 ± 3.6 9 months = 0.634
Squat 1 RM (kg)
Carb 23.7 ± 12.3 33.8 ± 14.4 43.7 ± 14.6 3 months = 0.722
Whey 20.4 ± 11.2 30.8 ± 14.3 35.8 ± 13.8 6 months = 0.759
Soy 22.4 ± 13.7 33.8 ± 14.2 39.8 ± 16.2 9 months = 0.279
Bench press 1 RM (kg)
Carb 10.3 ± 7.1 13.9 ± 7.5 16.0 ± 8.1 3 months = 0.450
Whey 11.7 ± 6.7 12.2 ± 16.8 20.1 ± 2.3 6 months = 0.879
Soy 9.1 ± 5.3 13.3 ± 5.7 15.9 ± 1.4 9 months = 0.200
RM = repetition maximum.
a
Values are mean ± SD. There were significant main time effects for body mass, lean body mass, percentage body fat, and maximal strength. In each case, values were
significantly different compared to baseline but not different at 3, 6, and 9 months.
∗
p < 0.05 from corresponding carb and soy values.
Fig. 2. Individual changes in lean body mass with 9 months of resistance
training in subjects supplemented with carbohydrate (n = 22), whey
protein (n = 19), or soy protein (n = 22). Diamonds = men, circles
= women. Boxes represent mean ± 95% confidence interval. Whey >
carb and soy by one-way analysis of variance.
of time on percentage body fat as shown by a decrease after
3 months that remained lower over the entire study, but there
were no group differences. There was a main effect of time on
maximal bench press and squat strength as shown by a significant
increase at 3 months that remained higher than baseline at 9
months. As expected with a resistance training program alone,
the carb, whey, and soy groups all showed a significant and
similar increase in maximal bench press (35%, 40%, and 36%,
respectively) and squat (62%, 44%, and 65%, respectively).
Fasting concentrations of leucine were significantly in-
creased (20%) in the whey group and remained unchanged in
the carb and soy groups. Exercise-induced plasma amino acid
patterns closely followed the amino acid composition of sup-
plements consumed immediately after resistance exercise (see
Table 5). Plasma leucine increased more than 2-fold 60 minutes
after exercise in the whey group, whereas values were slightly
increased in the soy group and decreased in the carb group (see
Fig. 3). The same response patterns were observed in plasma
BCAA and EAA, with the whey group showing a near doubling
in concentration 60 minutes postexercise compared to a more
moderate response in the soy group.
There were few significant correlations among plasma amino
acids and changes in lean body mass with the exception of
leucine. Several measures of leucine at different time points
were positively correlated with changes in lean body mass; the
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Table 5. Resistance Exercise-Induced Plasma Amino Acid Responses
a
Pre-exercise 15 Minutes 30 Minutes 60 Minutes AUC AUC ANOVA
Alanine Pretraining
Carb 212 ± 48 336 ± 61 342 ± 71 299 ± 79 22,929 ± 4112 T: 0.501
Whey 212 ± 79 324 ± 84 375 ± 90 432 ± 112 25,390 ± 6107 G: 0.090
Soy 229 ± 71 340 ± 97 370 ± 82 389 ± 98 25,266 ± 6113 G × T: 0.664
Posttraining
Carb 243 ± 50 359 ± 79 368 ± 82 344 ± 103 25,177 ± 5379
Whey 229 ± 85 352 ± 130 369 ± 137 440 ± 130 26,243 ± 7856
Soy 224 ± 54 349 ± 91 383 ± 73 416 ± 115 26,067 ± 5439
Arginine Pretraining
Carb 61 ± 20 59 ± 22 56 ± 19 52 ± 20 4275 ± 1492 T: 0.026
Whey 57 ± 19 62 ± 19 74 ± 22 89 ± 23 5251 ± 1328 G: 0.020
Soy 52 ± 20 58 ± 19 76 ± 24 91 ±
26 5153 ± 1365 G × T: 0.025
Posttraining
Carb 70 ± 23 68 ± 25 66 ± 20 62 ± 21 4995 ± 1613
Whey 55 ± 20 58 ± 20 67 ± 26 85 ± 24 4918 ± 1463
Soy 65 ± 16 72 ± 25 94 ± 38 114 ± 45 6426 ± 2067
∗
Asparagine Pretraining
Carb 29 ± 834± 22 35 ± 22 33 ± 24 2466 ± 1264 T: 0.198
Whey 28 ± 928± 838± 12 53 ± 19 2660 ± 768 G: 0.017
Soy 31 ± 12 32 ± 12 43 ± 24 51 ± 25 2911 ± 1287 G × T: 0.477
Posttraining
Carb 38 ± 15 34 ± 14 35 ± 13 35 ± 16 2615 ± 1082
Whey 34 ± 931± 838± 17 54 ± 23 2895 ± 904
Soy 36 ± 13 38 ± 17 49 ± 23 60 ± 28 3383 ± 1377
Citruline Pretraining
Carb 22 ± 718± 517± 414± 4 1340 ± 344 T: 0.824
Whey 20 ± 518± 519± 520± 6 1429 ± 356 G: 0.037
Soy 20 ± 418± 518± 518±
5 1363 ± 345 G × T: 0.908
Posttraining
Carb 23 ± 620± 518± 416± 4 1449 ± 350
Whey 22 ± 719± 619± 620± 6 1493 ± 406
Soy 21 ± 618± 519± 520± 7 1449 ± 404
Cysteine Pretraining
Carb 44 ± 10 43 ± 13 46 ± 13 45 ± 12 3333 ± 866 T: 0.116
Whey 49 ± 16 50 ± 18 58 ± 20 67 ± 31 4033 ± 1647 G: 0.002
Soy 44 ± 17 41 ± 18 45 ± 19 46 ± 18 3268 ± 1341 G × T: 0.371
Posttraining
Carb 46 ± 14 45 ± 16 47 ± 12 49 ± 15 3488 ± 1040
Whey 55 ± 21 52 ± 19 60 ± 26 77 ± 42 4487 ± 1753
Soy 50 ± 19 47
± 18 53 ± 21 54 ± 18 3800 ± 1394
Glutamate Pretraining
Carb 58 ± 21 82 ± 33 83 ± 32 73 ± 26 5653 ± 1802 T: 0.283
Whey 59 ± 27 90 ± 39 102 ± 45 105 ± 55 6776 ± 270 G:5 0.186
Soy 62 ± 26 81 ± 36 90 ± 33 84 ± 34 6055 ± 2234 G × T: 0.799
Posttraining
Carb 56 ± 21 81 ± 27 79 ± 32 73 ± 33 5536 ± 1881
Whey 67 ± 28 92 ± 33 100 ± 39 124 ± 62 6382 ± 2134
Soy 53 ± 23 74 ± 27 83 ± 29 82 ± 38 5548 ± 2012
Glutamine Pretraining
Carb 740 ± 190 730 ± 196 738 ± 201 707 ± 211 54,734 ± 14,147 T: 0.103
Whey 760 ± 194 754 ± 190 809 ± 196 905 ± 245 60,141 ± 14,166 G: 0.025
Soy 686 ± 184 677 ± 193 718 ± 183 759 ± 196 53,692 ± 13,819 G × T: 0.551
Posttraining
Carb 834 ± 151 821 ± 131 821 ± 169 806 ± 157 61,556 ± 10,737
Whey 829 ± 155 782 ± 154 826 ± 190 880 ± 272 67,827 ± 28,026
Soy 712 ± 140 696 ± 155 752 ± 124 821 ± 164 55,583 ± 10,202
(Continued on next page)
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Table 5. Resistance Exercise-Induced Plasma Amino Acid Responses
a
(Continued)
Pre-exercise 15 Minutes 30 Minutes 60 Minutes AUC AUC ANOVA
Glycine Pretraining
Carb 184 ± 72 177 ± 78 175 ± 74 163 ± 70 13,114 ± 5427 T: 0.570
Whey 175 ± 56 164 ± 59 176 ± 49 199 ± 69 13,266 ± 4084 G: 0.865
Soy 159 ± 67 148 ± 62 164 ± 76 178 ± 82 12,068 ± 5226 G × T: 0.955
Posttraining
Carb 188 ± 56 175 ± 59 176 ± 62 174 ± 59 13,332 ± 4293
Whey 181 ± 67 166 ± 64 180 ± 78 195 ± 82 13,409 ± 5295
Soy 158 ± 46 147 ± 43 158 ± 46 181 ± 62 11,955 ± 3510
Histidine Pretraining
Carb 105 ± 42 120 ± 46 110 ± 47 99 ± 41 8237 ± 3115 T: 0.188
Whey 117 ± 38 148 ± 55 140 ± 44 128 ± 37 9905 ± 3060 G: 0.616
Soy 98 ± 33 131 ± 60 112 ± 36 110 ±
30 8596 ± 2914 G × T: 0.902
Posttraining
Carb 100 ± 39 116 ± 42 106 ± 36 106 ± 43 7968 ± 2971
Whey 118 ± 42 149 ± 67 128 ± 51 122 ± 38 9819 ± 3585
Soy 101 ± 29 124 ± 49 116 ± 39 111 ± 29 8580 ± 2580
Isoleucine Pretraining
Carb 57 ± 17 55 ± 19 55 ± 19 42 ± 19 3953 ± 1213 T: 0.000
Whey 59 ± 10 71 ± 19 116 ± 56 162 ± 51 7522 ± 2202 G: 0.402#
Soy 58 ± 15 61 ± 17 83 ± 34 96 ± 32 5550 ± 1583 G × T: 0.907
Posttraining
Carb 60 ± 17 60 ± 25 52 ± 14 42 ± 14 4026 ± 1295
Whey 68 ± 20 73 ± 20 113 ± 64 172 ± 72 7786 ± 2887
Soy 60 ± 12 64
± 17 83 ± 27 97 ± 30 5664 ± 1367
Leucine Pretraining
Carb 110 ± 34 106 ± 39 103 ± 31 80 ± 28 7544 ± 2256 T: 0.000
Whey 108 ± 21 125 ± 29 182 ± 71 265 ± 88 12,505 ± 3305 G: 0.074#
Soy 106 ± 25 111 ± 26 142 ± 51 157 ± 48 9798 ± 2392 G × T: 0.157
Posttraining
Carb 115 ± 36 110 ± 38 103 ± 35 85 ± 30 7538 ± 2451
Whey 130 ± 36 142 ± 35 199 ± 89 290 ± 97 13,973 ± 3986
Soy 110 ± 20 119 ± 36 146 ± 45 162 ± 49 10,058 ± 2517
Methionine Pretraining
Carb 11 ± 410± 311± 410± 4 801 ± 246 T: 0.000
Whey 12 ± 412± 316± 418± 4 1077 ± 260 G: 0.001#
Soy 12 ± 412± 313± 414± 4 950 ± 268 G × T: 0.557
Posttraining
Carb 12 ± 312± 311± 211± 4 867 ± 189
Whey 14 ± 414± 417± 420± 4 1200 ± 259
Soy 13 ± 313± 316± 416± 3 1089 ± 216
Ornithine Pretraining
Carb 68 ± 28 58 ± 18 60 ± 20 54 ± 17 4489 ± 1419 T: 0.406
Whey 62 ± 26 63 ± 21 70 ± 22 78 ± 23 5089 ± 1596 G: 0.252
Soy 62 ± 20 61 ± 17 70 ± 18 79 ± 25 5064 ± 1360 G × T: 0.850
Posttraining
Carb 63 ± 27 57 ± 24 57 ± 25 55 ± 24 4320 ± 1831
Whey 56 ± 18 59 ± 17 61 ±
18 71 ± 23 4606 ± 1348
Soy 65 ± 33 62 ± 30 66 ± 34 68 ± 26 4875 ± 2158
Phenylalanine Pretraining
Carb 41 ± 13 40 ± 10 42 ± 19 37 ± 20 3012 ± 904 T: 0.003
Whey 45 ± 12 49 ± 17 55 ± 18 62 ± 16 3822 ± 911 G: 0.001#
Soy 42 ± 18 45 ± 17 53 ± 20 58 ± 22 3708 ± 1370 G × T: 0.094
Posttraining
Carb 51 ± 17 48 ± 15 47 ± 14 44 ± 16 3545 ± 1077
Whey 52 ± 15 51 ± 13 53 ± 15 61 ± 16 4046 ± 922
Soy 55 ± 17 59 ± 20 71 ± 26 77 ± 24 4901 ± 1455
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Table 5. Resistance Exercise-Induced Plasma Amino Acid Responses
a
(Continued)
Pre-exercise 15 Minutes 30 Minutes 60 Minutes AUC AUC ANOVA
Proline Pretraining
Carb 191 ± 72 199 ± 67 217 ± 79 202 ± 75 15,255 ± 5331 T: 0.097
Whey 193 ± 66 213 ± 67 261 ± 65 335 ± 85 18,581 ± 4636 G: 0.248
Soy 175 ± 52 187 ± 49 227 ± 53 255 ± 64 15,765 ± 3874 G × T: 0.192
Posttraining
Carb 219 ± 65 221 ± 63 237 ± 68 236 ± 68 17,133 ± 4657
Whey 201 ± 61 211 ± 57 253 ± 77 340 ± 108 18,532 ± 4926
Soy 170 ± 48 186 ± 48 224 ± 44 261 ± 62 15,701 ± 3296
Serine Pretraining
Carb 82 ± 34 78 ± 37 78 ± 34 71 ± 32 5793 ± 2535 T: 0.649
Whey 77 ± 39 73 ± 36 95 ± 56 123 ± 68 6770 ± 3489 G: 0.166
Soy 74 ± 40 71 ± 38 87 ± 55 94 ±
50 6070 ± 3401 G × T: 0.469
Posttraining
Carb 89 ± 32 82 ± 31 81 ± 27 80 ± 28 6123 ± 2129
Whey 79 ± 41 74 ± 39 94 ± 68 124 ± 72 6830 ± 3907
Soy 83 ± 39 84 ± 44 101 ± 48 115 ± 58 7134 ± 338
Taurine Pretraining
Carb 12 ± 414± 413± 413± 4 1047 ± 368 T: 0.396
Whey 12 ± 314± 414± 414± 4 1005 ± 226 G: 0.000
Soy 11 ± 313± 512± 511± 4 902 ± 308 G × T: 0.533
Posttraining
Carb 15 ± 617± 617± 717± 6 1236 ± 389
Whey 16 ± 617± 620± 819± 8 1365 ± 480
Soy 15 ± 516
± 517± 617± 5 1233 ± 374
Threonine Pretraining
Carb 80 ± 47 81 ± 50 83 ± 48 77 ± 46 6057 ± 3521 T: 0.204
Whey 90 ± 56 90 ± 56 118 ± 78 166 ± 112 8504 ± 5300 G: 0.025
Soy 84 ± 67 81 ± 63 102 ± 93 112 ± 99 7051 ± 5992 G × T: 0.495
Posttraining
Carb 94 ± 53 85 ± 52 90 ± 50 91 ± 47 6707 ± 3711
Whey 113 ± 66 103 ± 64 137 ± 98 187 ± 127 9896 ± 6185
Soy 89 ± 50 86 ± 51 104 ± 58 121 ± 80 7423 ± 4317
Tryptophan Pretraining
Carb 34 ± 11 30 ± 935± 14 34 ± 15 2496 ± 723 T: 0.000
Whey 32 ± 12 37 ± 745± 10 63 ± 12 3269 ± 601 G: 0.000#
Soy 39 ± 16 38 ± 14 42 ± 15 47 ± 17 3073 ± 1124 G × T: 0.158
Posttraining
Carb 38 ± 16 34 ± 13 35 ± 13 37 ± 17 2675 ± 1036
Whey 45 ± 14 47 ± 13 54 ± 15 71 ± 16 4017 ± 963
Soy 45 ± 16 47 ± 15 54 ± 16 61 ± 17 3851 ± 1080
Valine Pretraining
Carb 230 ± 135 230 ± 144 233 ± 153 195 ± 114 16,802 ± 10,220 T: 0.322
Whey 212 ± 68 230 ± 130 270 ± 164 360 ± 160 19,811 ± 9661 G: 0.018
Soy 212 ± 106 201 ± 70 234 ± 83 252 ± 83 16,748 ± 6023 G × T: 0.362
Posttraining
Carb 253 ± 159 254 ± 167 241 ± 158 214 ± 132 18,130 ± 11,564
Whey 251 ± 81 255 ± 93 313 ±
196 388 ± 220 22,373 ± 10,886
Soy 211 ± 52 212 ± 56 240 ± 54 257 ± 67 17,196 ± 3896
AUC = area under the curve; ANOVA = analysis of variance; T = main time effect; G = main group effect; T × G = Time × Group effect.
a
Values are mean ± SD. Subjects performed squat (6 sets, 10 repetitions) followed immediately by consumption of carbohydrate, whey, or soy supplements. AUC data
analyzed by 2 × 3 ANOVA.
∗
Indicates significant difference (p < 0.05) from a ll other values.
#Indicates that whey and soy were significantly different (p < 0.05) from carb.
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Resistance Training and Protein Supplementation
Fig. 3. Plasma leucine, branched-chain amino acid, and essential amino acid responses to a resistance exercise workout (6 sets of 10 repetitions) before
and after 9 months of training.
most significant was fasting plasma leucine at 9 months versus
changes in lean body mass (see Fig. 4). Although there was
considerable overlap in fasting plasma leucine levels among
individuals in the different groups, several subjects in the carb
and soy groups had fasting values less than 100 μmol · L
−1
,
whereas only one subject in the whey group fell below this
arbitrary threshold. Within the group of individuals with fasting
plasma leucine < 100 μmol · L
−1
, it is interesting to note than
no one showed an increase in lean body mass greater than 4 kg
(see Fig. 4).
DISCUSSION
Despite consistent research documenting the transient an-
abolic action of whey protein postexercise, there is a lack of
research linking acute responses to chronic adaptations to train-
ing. This study was unique in that it (1) was the longest resistance
training study to date investigating protein supplementation (9
months), (2) was the first to directly compare 2 isocaloric pro-
tein sources as well as a carbohydrate control, (3) involved a su-
pervised resistance training program that included whole-body
exercises, and (4) controlled protein intake throughout the inter-
vention. Our results indicate that protein quality is an important
determinant of lean body mass responses to resistance training in
the context of untrained individuals consuming protein at levels
slightly greater than the RDA but well within the normal range of
protein intake for this population. There was a superior effect of
whey protein supplementation accumulation of lean body mass
with effects evident after 3 months and sustained throughout 9
months of training. Isocaloric supplementation with soy protein
or carbohydrate was less effective in promoting gains in lean
body mass. Whey supplementation was associated with higher
fasting and exercise-induced elevations in plasma leucine, which
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Fig. 4. Scatterplot of fasting plasma leucine at 9 months versus change in lean body mass from baseline to 9 months. Correlation coefficient (R
2
) =
0.17, p < 0.005.
may account, in part, for greater anabolic effects in skeletal
muscle.
A growing number of resistance training interventions have
investigated the effects of protein supplementation, but few have
involved long-term supervision of training and control of diet
over periods longer than 3 months. A recent meta-analysis ex-
amined whether protein supplementation augments muscle mass
with prolonged resistance training [25]. A total of 22 studies
ranging from 6 to 24 weeks were analyzed. Carbohydrate was
the placebo in most studies, and the source of protein was milk
protein (whey or some combination of whey with other protein).
Compared to placebo, protein supplementation resulted in an
additional 0.7 kg gain in lean body mass over 3 months. This
is the same additional gain in lean body mass observed in the
present study for the whey and carb groups at 3 months.
Lean body mass increased after 3 months and plateaued at
6 and 9 months, indicating that the majority of gains in mus-
cle mass can be achieved after 36 workouts in non-strength-
trained recreationally active young adults. The greater gains in
lean body mass observed in the whey group did not translate
into greater gains in maximal strength. Maximal strength is only
partially related to muscle size, and it is not uncommon for resis-
tance training-induced adaptations in muscle mass and maximal
strength to be disconnected [26]. Nevertheless, the change in
lean body mass at 3 months was significantly associated with
the change in maximal squat and bench press at 3 months (r =
0.40 and 0.48, respectively). However, other variables such as
neural adaptations have a greater contribution and are likely
not impacted by whey supplementation. In addition, the varied
exercises performed during training likely resulted in muscle
mass gains that were distributed over the whole-body muscula-
ture, which would lessen the likelihood of manifesting in greater
strength in a specific movement.
There was no difference in lean body mass response be-
tween the carb and soy groups, indicating that simply increas-
ing protein intake from 1.1 to 1.4 g · kg body mass
−1
is not
adequate to optimize muscle gains to resistance training. This
highlights the importance of protein quality over quantity within
this range of protein intakes. There was no difference in fat mass
responses between groups, but it is worth noting that fat mass
did decrease, resulting in a significant decrease in percentage
body fat for all groups. Thus, the gains in body mass for all
groups, and the greater gains in the whey group, were attributed
to gains in lean body mass. The lack of increase in fat mass, and
an actual slight decline, is important from health and aesthetic
perspectives.
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Resistance Training and Protein Supplementation
The mechanism(s) underlying the greater adaptive response
to whey in lean body mass could be related to the greater avail-
ability of leucine. Leucine, and more generally BCAA, are well-
documented fuels for muscle, but they are also potent signals
activating an anabolic/anticatabolic program in skeletal muscle
[27]. Ingestion of whey is clearly more effective than ingestion
of soy protein at elevating circulating levels of BCAA, as well
as total EAA postexercise (see Fig. 3). Peak concentrations of
leucine were elevated more than 2-fold postexercise, and this
has been shown to be of sufficient magnitude to elicit a robust
increase in net muscle protein synthesis [28]. The cumulative
effect of these daily anabolic surges, although transient, may be
important to optimize gains in muscle mass. The 0.7 kg greater
increase in lean body mass over the first 12 weeks would trans-
late into an additional incorporation of only 1–2 g · day
−1
of
amino acids into skeletal muscle. Whey protein also increased
fasting leucine levels on average 20%. This modest increase in
basal leucine availability is surely a much weaker anabolic sig-
nal than the transient postprandial surges, but the total exposure
of skeletal muscle to slightly elevated leucine over a 24-hour
period could have a role in the adaptive response to resistance
training. Interestingly, it was the fasting plasma leucine concen-
tration that was most highly correlated with gains in lean body
mass (see Fig. 4).
We do not know whether the protocol of whey ingestion
used in this study (i.e., 22 g consumed immediately postexer-
cise) is optimal. Previous studies have shown that 20 g of egg
protein produced a maximal increase in muscle protein synthe-
sis with no further increase with ingestion of 40 g in young
individuals [29]. Better nitrogen retention was observed when
resistance-trained men consumed whey protein in doses of 10–
20 g per serving postexercise compared to larger doses given
in bolus [30]. In regards to timing, there is evidence that pre-
exercise ingestion may stimulate muscle protein synthesis to a
greater degree than ingestion after resistance exercise [31], but
this study used free amino acids. A follow-up study by this group
showed that ingestion of 20 g of whey protein before or after re-
sistance exercise resulted in the same increase in muscle protein
synthesis [13].
CONCLUSIONS
In conclusion, daily supplementation with ∼20 g whey pro-
tein during resistance training is an effective strategy for aug-
menting gains in lean body mass in young, healthy, untrained
men and women consuming protein levels slightly above the
RDA. Gains in lean body mass occurred in the context of stable
or small decreases in fat mass. These results point to protein
quality as an important determinant of the adaptive response to
whole-body resistance training.
ACKNOWLEDGMENTS
The authors thank a dedicated group of subjects and the
research and medical staffs at the University of Connecticut for
their support. This study was funded by a grant from the Dairy
Research Institute, Rosemont, Illinois.
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Received May 1, 2012; revision accepted March 18, 2013.
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