Carbohydrate-Protein Supplementation and Performance
22
Journal of Exercise Physiologyonline
(JEPonline)
Volume 13 Number 3 June 2010
Managing Editor
Tommy Boone, PhD, MPH
Editor-in-Chief
Jon K. Linderman, PhD
Review Board
Todd Astorino, PhD
Julien Baker, PhD
Tommy Boone, PhD
Eric Goulet, PhD
Robert Gotshall, PhD
Alexander Hutchison, PhD
M. Knight-Maloney, PhD
Len Kravitz, PhD
James Laskin, PhD
Derek Marks, PhD
Cristine Mermier, PhD
Chantal Vella, PhD
Ben Zhou, PhD
Official
Research Journal of
the American Society of
Exercise Physiologists
(ASEP)
ISSN 1097-9751
Nutrition and Exercise
The Effects of a Carbohydrate-Protein Drink on Performance and
Mood in U.S. Pararescue Trainees
HEATH GASIER1 and CRAIG OLSON 2
1Naval
Submarine Medical Research Laboratory, Groton, Connecticut,
USA, 2Salus Education, LLC, San Antonio, Texas, USA
ABSTRACT
Gasier HG, Olson CA. The Effects of a Carbohydrate-Protein Drink on
Performance and Mood in U.S. Pararescue Trainees. JEPonline
2010;13(3):22-31. Carbohydrate-protein (CHO-PRO) beverages have
been reported to improve endurance performance; however, no studies
have been conducted on elite military combatants in a field setting in a
fed state. Thus, the primary objective of this study was to evaluate the
effects of a CHO-PRO supplement on physical performance and mood
in U.S. Air Force Pararescue indoctrination trainees. Eight, healthy U.S.
Air Force Pararescue indoctrination trainees completed a double-blind,
randomized crossover study. Following a morning meal (592 kcal),
subjects completed a 2000 m swim, physically demanding water
activities, calisthenics (push-ups, pull-ups, curl-ups and flutter-kicks), a
6.4 km run, and a 400 m exhaustive run. Supplements (600 ml x 5
doses) were provided throughout the study and consisted of a placebo
(PLA), an 8.9% carbohydrate solution (CHO), and a 7.22%
carbohydrate/1.81% protein solution (CHO-PRO). Times (minutes and
seconds) and repetitions were used to assess physical performance,
and subjective mood states were determined using the Profile of Mood
States Questionnaire (POMS). No differences were observed between
the CHO-PRO, CHO, and PLA groups on any of the physical
performance measures or mood states. These results suggest that, in
the fed state, a CHO-PRO beverage does not enhance physical
performance or mood during a series of physically demanding activities
lasting < 1 h in duration in U.S. Air Force Pararescue indoctrination
trainees.
Key Words: Cognitive Performance, Ergogenic, Special Forces
Carbohydrate-Protein Supplementation and Performance
23
INTRODUCTION
The addition of protein (~2.0%) to carbohydrate solutions has been reported to enhance exercise
performance (timed performance or time to fatigue) (3, 10, 12-14), attenuate postexercise muscle
damage (7, 12-14, 16, 18), and decrease mood disturbances (when repeated bouts of exercise are
performed) (16). The ergogenic properties of adding protein have been suggested to be due to either
a sparing of blood glucose/glycogen and an increase in protein oxidation, a reduction in the ratio of
free tryptophan to branched chain amino acids, enhanced intestinal fluid/fuel transport, and/or an
increase in insulin secretion (11). However, it may be more easily explained by the additional energy
from protein, as those that provided isocaloric supplements observed no additive benefit (16, 18).
Thus, more research in this area is required to determine whether a carbohydrate-protein supplement
is advantageous for improving performance.
U.S. Special Forces training imposes a significant degree of physical and cognitive stress on the
trainees, which ultimately results in high attrition impacting the number of trained combatants. The
physical training in many ways resembles that of an endurance athlete, thus adhering to the same
principles for optimizing performance and aiding in recovery would seem beneficial to this population.
Therefore, due to the ergogenic potential of a carbohydrate-protein supplement, we sought to
determine the effectiveness of carbohydrate-protein supplementation in an elite combatant training
environment (i.e., a field study). In addition, we wanted to conduct this experiment in the trainee’s
natural environment without removing the influence of prior feeding and water consumption. We
compared the effects of a 7.22% carbohydrate/1.81% protein beverage, an isocaloric 8.9%
carbohydrate beverage and a nonenergetic placebo consumed on 5 occasions (600 ml per
beverage), in the fed state, over the course of a training day on physical performance and mood in
U.S. Pararescue trainees. Using a double-blind, placebo-controlled, repeated-measures cross-over
design, we tested the hypotheses: 1) carbohydrate-protein supplementation would improve physical
performance compared to isocaloric carbohydrate and placebo supplements; and 2) carbohydrateprotein supplementation would improve mood compared to isocaloric carbohydrate and placebo
supplements.
METHODS
Subjects
The subjects consisted of eight healthy males (Table 1) who were undergoing their eighth week of
training during the 10-week U.S. Air Force Pararescue Indoctrination course (Lackland Air Force
Base, San Antonio, TX). There were initially 83 trainee’s
Table 1. Physical characteristics of subjects
enrolled in the course; however, due to the high attrition
Parameter
Value
rate of Pararescue training (~80% on average), only those
Age (yrs)
23.8 ± 2.0
that remained after the final evaluation during week 7 were
Height (cm)
178.6 ± 2.4
considered for study enrollment (considered to be highly
Weight (kg)
77.8 ± 2.9
“trained”). Each subject voluntarily agreed to participate in
BMI (kg/m2)
24.4 ± 0.6
the study and signed an informed consent document prior
Body fat (%)
8.4 ± 0.7
to participation. The 59th Medical Wing Institutional Review
RMR (kcal)
1668.0 ± 105
Board at Lackland Air Force Base, San Antonio, TX
Values are means ± SE.
approved the study.
Procedures
Experimental Protocol
The study used a double-blind, placebo-controlled, randomized block design. Each subject received a
7.22%/1.81% carbohydrate-protein solution (CHO-PRO), an 8.9% carbohydrate solution (CHO) and
Carbohydrate-Protein Supplementation and Performance
24
an aspartame-sweetened solution (PLA) in a randomized manner separated by 1 day of training. A
washout period greater than 1 day was not possible due to the training demands and the limited time
that was available to conduct and complete this study (1 week). We do not feel that this was a
methodological limitation due to employing a randomized block design, the intense training that the
study participants underwent on the non-study days, and the adequate time/meals that were available
for the trainees to replenish any depletion in glycogen stores that may have existed.
Two days prior to the start of test day one, all participants reported to the Pararescue Indoctrination
training center to receive detailed instructions of the study design. At this time, skinfolds of the chest,
abdomen, and thigh were obtained using Lange Skinfold Calipers (Cambridge Scientific Industries,
Cambridge, MD) to determine body fat percentage (4), and resting metabolic rate was measured
using the MedGem analyzer (Mead Johnson, Evansville, IN) (9) (Table 1). Following these
measurements, study participants were familiarized with the Profile of Mood States (POMS)
questionnaire. Prior to dismissal, subjects were instructed to maintain their normal diet 24-hours prior
to each test day and fast 6-hours prior to reporting to the training center on each test day during the
week of the study. A Registered Dietitian (HG) educated all subjects on nutrition for the endurance
athlete during their first week of training with special emphasis placed on consuming a high
carbohydrate diet ( 60% of total kcal consumed) throughout their training. All of the trainee’s meals
are provided by the base dining hall with the only restrictions being the time that is allotted to
consume the meals. Additionally, the trainees are allowed to have food in their lockers, thus snacking
in the evenings was encouraged.
On each of the three test days, the subjects reported at 0430 to perform a series of events that were
typical of Pararescue training (Table 2), with motivational encouragement provided, as normal, by the
Pararescue instructors. The principal aerobic activities Table 2. Approximate schedule of events
included the 2000 m swim, the instructor pool evolution during study days
and the 6.4 km run. The pool evolution was non-testable Activity
Time
and only served to fatigue the subjects. Activities during Check-in
0430
this 1-hour block consisted of treading water with a 6.8 kg First POMS
0435
weight attached to each subject, followed by repetitive 25 Meal & Treatment 1
0445
m submerged swims interspersed with immediate exits Swim (2000 m)
0545
from the pool for push-ups (negative reinforcement). The Treatment 2
0645
anaerobic (strength) activities were the calisthenics, which Instructor pool
0700
included 3 cycles of push-ups, curl-ups, flutter-kicks and evolution
Treatment 3
0800
pull-ups. The subjects completed the maximum number of Calisthenics
0915
repetitions of each exercise in 2 minutes with 5 minutes Treatment 4
1000
rest between each cycle. The exhaustive activity consisted Run (6.4 km)
1030
of completing as many 400 m run laps within their average
Exhaustive run (400 m)
1115
time as possible. The mean air temperature during the
Treatment 5
1130
three study days ranged from 14 ± 5º C with 94 ± 10%
Second POMS
1145
humidity at 0600 to 23 ± 1º C with 44 ± 7% humidity at
1200
1100. The mean water temperature was 27 ± 1º C on all Dismissal
See methods for detailed description.
three test days.
Calisthenics consisted of push-ups, pull-ups,
sit-ups and flutter-kicks (3 sets of each
exercise completed until exhaustion). POMS,
Profile of Mood States.
Prior to the start (0435) and following the completion
(1145) of each study day, subjects completed the POMS
questionnaire to assess mood (Table 2). The POMS was
selected for use in the present study because it is a rapid, reliable and economical method of
detecting transient fluctuations in six mood states: Tension-Anxiety, Depression-Dejection, AngerHostility, Vigor-Activity, Fatigue-Inertia, and Confusion-Bewilderment (8). In addition, the POMS has
Carbohydrate-Protein Supplementation and Performance
25
been used previously to assess mood changes in U.S. special forces personal (5, 6) and in
endurance athletes consuming carbohydrate-amino acid drinks (16).
Upon completion of the POMS questionnaire (1200), the trainees were dismissed for lunch and
returned for non-physical Pararescue training. On the days between study days, trainees completed
normal training which included physically and psychologically demanding activities, as normal. Due to
the short duration of the indoctrination course (10-weeks), it was not possible to implement rest days
for these subjects.
Morning Meal
At 0445 on each of the three test days, subjects were provided a morning meal that consisted of an
orange, banana, 3 oz bagel and 2 Tbsp of peanut butter supplying the subjects with 592 kcal, 87 g of
carbohydrates (59%), 21 g of protein (13 %), and 18.5 g of fat (28%). This meal was chosen due to
the trainee’s preference (i.e., what they typically would consume at breakfast). All of the subjects
consumed the morning meal on test days one and two, however, two subjects failed to consume the
entire meal on the final testing day (532 and 492 kcal).
Supplements
The CHO-PRO, CHO and PLA beverages were orange flavored and were prepared in accordance
with the manufacturer’s instructions (Pacific Health Laboratories, Inc., Woodbridge, NJ). Each subject
was provided 600 ml of a beverage in between the events for a total of 3 L (5 doses). In addition, we
allowed ad libitum water consumption throughout the study following beverage administration due to
the nature of the design (i.e., the subjects normally consume water and we didn’t want to disrupt
routine training practices). Each CHO-PRO treatment (4:1 ratio) provided 233 kcal, 43 g of
carbohydrate (~7.2%), 11 g of protein (~ 1.8%), and 1.8 g of fat. The CHO beverages provided 230
kcal, 53 g of carbohydrate (8.9%) and 1.8 g of fat. The PLA beverages provided no energy and
consisted of aspartame as the flavoring ingredient. The source of carbohydrate for both CHO-PRO
and CHO supplements was sucrose, fructose and maltodextrin (typical of commercially available
sports beverages). The protein for the CHO-PRO beverage was a whey concentrate. Of the five
treatments administered on the three test days, two subjects failed to finish the 3 L (2740 ml and
2400 ml) of the CHO-PRO, one was unable to consume all (2750 ml) of the PLA and all finished the
CHO.
Statistical Analyses
All data (performance and POMS) were analyzed by a one-way repeated measures analysis of
variance. All statistical analyses were completed with SPSS for Windows (version 11.5). The -level
of 0.05 was established as being significant.
RESULTS
Physical Performance
Data from the aerobic (2000 m swim and 6.4 km run), anaerobic (calisthenics) and exhaustive (400 m
run at 85% of maximum time) activities are shown in Table 3. All of the subjects completed the 2000
m swim; whereas, 8 subjects completed all 3 sets of the calisthenics (mean of all 3 cycles) with the
CHO and PLA, and 7 with the CHO-PRO beverages. In addition, 7 subjects completed the 6.4 km run
with the CHO-PRO and PLA beverages. The two subjects that did not finish the run with the CHOPRO and PLA treatments did complete 4.4 km and 4.0 km respectively. There were no differences
(p>0.05) observed between treatments with any of the physical activities, including the exhaustive
run.
Carbohydrate-Protein Supplementation and Performance
26
Mood Performance
The POMS 6 subscales were used to assess Total Mood Disturbance (TMD), a single global
assessment of affective state (Table 3). A negative TMD change score indicated improved mood
whereas a positive TMD score
Table 3. Indices of physical performance and mood states in
represented a worsened mood.
Pararescue indoctrination trainees
CHO-PRO
CHO
PLA
No differences (p>0.05) were
observed for any of the 6 mood
Physical Performance
Swim (2000 m)
37.5 ± 0.7
37.6 ± 0.7
37.2 ± 0.7
states, thus only TMD scores are
shown.
Push-ups
79.4 ± 3.0
76.6 ± 2.6
79.1 ± 4.1
Curl-ups
75.8 ± 1.9
76.1 ± 2.7
75.5 ± 2.7
Pull-ups
14.0 ± 0.6
14.2 ± 0.6
14.2 ± 0.9
Flutter-kicks
85.9 ± 1.7
87.5 ± 2.5
88.5 ± 1.5
Run (6.4 km)
28.5 ± 0.6
28.8 ± 0.9
28.6 ± 0.8
Exhaustive run (400 m)
0.1 ± 0.1
0.4 ± 0.2
0.3 ± 0.2
Perception of Mood States
TMD (change from pre-to
-6.5 ± 5.0
-8.5 ± 9.2
-5.0 ± 7.1
post)
Values are means ± SE. There were no significant (p>0.05) differences
DISCUSSION
We set out to determine whether
a carbohydrate-protein beverage
consumed over the course of a
typical, intense, day of training in
U.S. Air Force Pararescue
trainees
improved
physical
between the carbohydrate-protein (CHO-PRO), carbohydrate (CHO) or
performance and mood. Contrary
placebo (PLA) groups (n=7-8 per group) for and of the physical
performance measures or mood. Calisthenics (push-ups, curl-ups, pull-ups
to our hypotheses, we did not find
and flutter-kicks) are presented as the mean repetitions of the 3 sets, the
an ergogenic effect of a
2000 m swim and 6.4 km run are presented in minutes, and the 400 m
carbohydrate-protein supplement.
exhaustive run is presented as the maximal number of 400 m laps
Although we employed a different
completed. TMD, total mood disturbance.
experimental design (field vs.
laboratory), our data are in agreement with reports by others that did not find a beneficial effect of
protein on endurance (16, 18, 19) and resistance (1) exercise. Our findings may be explained by the
morning meal supplied 1 h prior to the start of the study and/or the nature of the activities performed
(all were < 1 h in duration).
The initial studies that have examined the effectiveness of a carbohydrate-protein supplement on
endurance performance enhancement, and who observed a benefit, either failed to report (12, 13) or
did not provide a meal (3, 10) prior to the start of the study. The principle behind these experimental
designs is to deplete or attenuate skeletal muscle glycogen levels during the exercise protocol to
determine if a nutrient(s) are ergogenic, and therefore, prior feeding is avoided due to the potential for
masking any effect. However, one must acknowledge that these designs do not accurately represent
an athlete’s daily training regimen, or Special Forces training for that matter, and may not always
allow for generalizations to be made. Moreover, it would have been unrealistic to conduct our
experiment during training without providing a morning meal similar to what they normally consume.
Interestingly, those that either reported providing a meal prior to exercise testing (2, 14, 19), or
administered isocaloric beverages (16, 18) did not observe improvements in “overall” time-trial
performance in the former or time to exhaustion in the latter studies, consistent with our findings. As a
result of these investigations, along with our findings, it would appear that prior feeding and/or
providing isocaloric supplements may remove the ergogenic properties of carbohydrate-protein.
However, since there were no within or between treatment differences (i.e., no effect of
carbohydrate), it is difficult to conclude that isocaloric supplements are the sole reason for not
observing improvements in performance.
Of the investigations that reported no improvements in overall time-trial performance (14, 19), time to
exhaustion (16, 18) or with resistance exercise (1), only Van Essen et al. (19) and Valentine et al.
(18) compared carbohydrate-protein, carbohydrate and placebo groups. Both groups reported
Carbohydrate-Protein Supplementation and Performance
27
differences over placebo and Van Essen et al. (19) provided feeding 2-3 h prior to the start of
exercise, thus we would have expected to see improvements with carbohydrate-protein or
carbohydrate vs. placebo. The morning meal was provided 1 h prior to the first activity, the 2000 m
swim, and supplied 8 ± 0.8 kcal ∙ kg body mass-1. Based on comparisons to other military populations
(17), this quantity of energy likely provided no more than ~15% of the trainees total daily energy
requirements, which would seem unlikely to be a sufficient amount of energy to support maximal
performance over the duration of the study. Thus, the morning meal alone cannot explain the lack of
an ergogenic effect of the carbohydrate-protein or carbohydrate beverages.
A more plausible explanation for not observing any treatment differences may be the type and
duration of the endurance and strength activities (common to Pararescue training) that the subjects
performed during the study (Table 2). Of the studies that have examined the effectiveness of
carbohydrate-protein supplements on exercise performance, all but two (1, 7) employed endurance
protocols lasting 1 h or greater. Interestingly, these studies did not observe an improvement in
resistance exercise performance (1) or in 5-8 km cross-country race times (7) with a carbohydrateprotein beverage. In fact, the former investigation reported no differences between carbohydrateprotein and the placebo group, similar to our findings. These data suggest that carbohydrate
with/without protein is not effective in improving performance in physical activities less than 1 h in
duration. The design of the experiment did not allow for determining the physiological mechanism
(beyond the scope of this study). However, a likely explanation is that prior feeding in combination
with physically demanding activities of short duration (< 1 h) allowed for glycogen preservation and
maintenance of blood glucose, thus sustainment of performance.
The effects of carbohydrate-protein on total mood disturbance, assessed by the POMS, were similar
to the effects on physical activity. The premise for including this as an outcome variable is that
Special Forces training is not only physiologically demanding, but also psychologically grueling as
well, serving to prepare trainees for combat. This stress results in a deterioration of cognitive function
(5) and the POMS (confusion and vigor) can be used as an instrument to indirectly measure cognitive
states (15). Providing carbohydrate to U.S. Army Rangers has been reported to attenuate confusion
and improve vigor during a day of sustained training (6). Additionally, carbohydrate-protein
supplementation attenuated the feeling of fatigue with consecutive bouts of exhaustive endurance
exercise (16). Taken together, it would seem plausible carbohydrate-protein or carbohydrate
supplementation would have improved total mood disturbance or at least one of its subscales. This
observation may be explainable by the maintenance of blood glucose and available substrate for the
brain; and/or due to the trainees becoming accustomed to the rigors of training as they made it
through the most common phases of attrition (initial 5 weeks).
A limitation to this study was the limited sample size (n=8). As a result of the rigors of the Pararescue
Indoctrination course, the pool of trainees that could be potential subjects is variable due to attrition.
We wanted to examine those individuals that endured the most physically and psychologically
demanding period of the training (i.e., the first 6 weeks). At week 7, when recruitment occurred, 10
trainees remained, however, two were injured and could not perform all of the physical tasks
optimally, and thus 8 were available to participate in this study. Although we do not feel it is a likely
explanation, the lack of a statistical difference between treatments may be due to the inability to
detect changes < 8.5%. More specifically, for the 2000 m swim there were only 1.3% and 1.0%
differences between the CHO vs. PLA and CHO-PRO vs. PLA group. Had we observed a 5.0%
difference, would this have been a large enough difference to suggest that further investigation is
warranted and recommend that Pararescue Indoctrination trainees consume CHO-PRO
supplements? In our opinion, a difference of this magnitude is not going to impact their performance
during the latter phase of their training as all of the trainees far exceeded the physical requirements.
Carbohydrate-Protein Supplementation and Performance
28
CONCLUSIONS
To our knowledge, this was the first study to examine the effectiveness of carbohydrate-protein
supplementation on aerobic and anaerobic activities, and mood in the fed state during U.S. Air Force
Special Forces training. Although there is appeal for these commercially available beverages for
improving performance in athletes, the data from laboratory controlled investigations may not always
be applicable to this type of training environment. Furthermore, an ergogenic effect may not be
realized with prior feeding and/or isocaloric supplements, and for repetitive physically demanding
activities lasting < 1 h in duration. Taken together, optimizing nutrient and fluid intake should be the
priority for sustaining performance in this environment.
ACKNOWLEDGEMENTS
This research was supported by the 59th Clinical Research Squadron, Lackland Air Force Base. We
extend our gratitude to the U.S. Air Force 342nd Training Squadron’s trainees and instructors for
voluntarily participating in this study, and to Benjamin J. Snyder, PhD, Anneke Bush, ScD, John Ivy,
PhD, Harris Lieberman, PhD, and Robert Portman, PhD for technical support.
Address for correspondence: Gasier HG, PhD, Naval Submarine Medical Research Laboratory,
Groton, Connecticut, USA, zip-code, 06349-5900. Phone: (860)694-4680; FAX: (860)694-2547;
email: heath.gasier@med.navy.mil.
REFERENCES
1.
Baty, J.J., Hwang, H., Ding, Z., Bernard, J.R., Wang, B., Kwon, B., and Ivy J.L. The effect of a
carbohydrate and protein supplement on resistance exercise performance, hormonal
response, and muscle damage. J Strength Cond Res 2007;21:321-329.
2.
Cermak, N.M., Solheim, A.S., Gardner, M.S., Tarnopolsky, M.A., and Gibala, M.J. Muscle
metabolism during exercise with carbohydrate or protein-carbohydrate ingestion. Med Sci
Sports Exerc 2009;41:2158-2164.
3.
Ivy, J.L., Res, P.T., Sprague, R.C., and Widzer, M.O. Effect of a carbohydrate-protein
supplement on endurance performance during exercise of varying intensity. Int J Sport Nutr
Exerc Metab 2003;13:382-395.
4.
Jackson, A.S., and Pollock, M.L. Practical assessment of body composition. Phys Sportsmed
1985;13:76-89.
5.
Lieberman, H.R., Bathalon, G.P., Falco, C.M., Morgan, C.A., 3rd, Niro, P.J., and Tharion, W.J.
The fog of war: decrements in cognitive performance and mood associated with combat-like
stress. Aviat Space Environ Med 2005;76:C7-14.
6.
Lieberman, H.R., Falco, C.M., and Slade, S.S. Carbohydrate administration during a day of
sustained aerobic activity improves vigilance, as assessed by a novel ambulatory monitoring
device, and mood. Am J Clin Nutr 2002;76:120-127.
Carbohydrate-Protein Supplementation and Performance
29
7.
Luden, N.D., Saunders, M.J., and Todd, M.K. Postexercise carbohydrate-protein- antioxidant
ingestion decreases plasma creatine kinase and muscle soreness. Int J Sport Nutr Exerc
Metab 2007;17:109-123.
8.
McNair, D.M., Lorr, M., and Droppelman, L.E. Edits manual for the profile of mood states. San
Diego, CA, 1992.
9.
Nieman, D.C., Trone, G.A., and Austin, M.D. A new handheld device for measuring resting
metabolic rate and oxygen consumption. J Am Diet Assoc 2003;103:588-592.
10.
Niles, E.S., Lachowetz, T., Garfi, J., Sullivan, W., Smith, J.C., Leyh, B.P., and Headley, S.A.
Carbohydrate-protein drink improves time to exhaustion after recovery from endurance
exercise J Exerc Physiol 2001;41:45-52.
11.
Saunders, M.J. Coingestion of carbohydrate-protein during endurance exercise: influence on
performance and recovery. Int J Sport Nutr Exerc Metab 2007;17:S87-S103.
12.
Saunders, M.J., Kane, M.D., and Todd, M.K. Effects of a carbohydrate-protein beverage on
cycling endurance and muscle damage. Med Sci Sports Exerc 2004;36:1233-1238.
13.
Saunders, M.J., Luden, N.D, and Herrick JE. Consumption of an oral carbohydrate-protein gel
improves cycling endurance and prevents postexercise muscle damage. J Strength Cond
Res 2007;21:678-684.
14.
Saunders, M.J., Moore, R.W., Kies, A.K., Luden, N.D., and Pratt, C.A. Carbohydrate and
protein hydrolysate coingestion's improvement of late-exercise time-trial performance. Int J
Sport Nutr Exerc Metab 2009;19:136-149.
15.
Shukitt-Hale, B., Banderet, L.E., and Lieberman, H.R. Elevation-dependent symptom, mood,
and performance changes produces by exposure to hypobaric hypoxia. Int J Aviat Psychol
1998;8:319-334.
16.
Skillen, R.A., Testa, M., Applegate, E.A., Heiden, E.A., Fascetti, A.J., and Casazza, G.A.
Effects of an amino acid carbohydrate drink on exercise performance after consecutive-day
exercise bouts. Int J Sport Nutr Exerc Metab 2008;18:473-492.
17.
Tharion, W.J., Lieberman, H.R., Montain, S.J., Young, A.J., Baker-Fulco, C.J., Delany, J.P.,
and Hoyt, R.W. Energy requirements of military personnel. Appetite 2005;44:47-65.
18.
Valentine, R.J., Saunders, M.J., Todd, M.K., and St Laurent, T.G. Influence of carbohydrateprotein beverage on cycling endurance and indices of muscle disruption. Int J Sport Nutr
Exerc Metab 2008;18:363-378.
19.
van Essen, M., and Gibala, M.J. Failure of protein to improve time trial performance when
added to a sports drink. Med Sci Sports Exerc 2006;38:1476-1483.
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