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Kephart, Roberts et al. (Amino Acids 2015) Ten weeks of Amino Acid supplementation in cyclists

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DOI 10.1007/s00726-015-2125-8
Amino Acids
Ten weeks of branched‑chain amino acid supplementation
improves select performance and immunological variables
in trained cyclists
Wesley C. Kephart1 · Taylor D. Wachs1 · R. Mac Thompson1 · C. Brooks Mobley1 ·
Carlton D. Fox1 · James R. McDonald1 · Brian S. Ferguson1 · Kaelin C. Young2 ·
Ben Nie3 · Jeffrey S. Martin1,4 · Joseph M. Company5 · David D. Pascoe1,4 ·
Robert D. Arnold3 · Jordan R. Moon6 · Michael D. Roberts1,4
Received: 7 April 2015 / Accepted: 28 October 2015
© Springer-Verlag Wien 2015
total lean mass (P = 0.27) or dual-leg lean mass (P = 0.96).
A significant interaction existed for body mass-normalized
relative peak power (19 % increase in the BCAA group
pre- to post-study, P = 0.01), and relative mean power (4 %
increase in the BCAA group pre- to post-study, P = 0.01).
4 km time-trial time to completion approached a signifi-
cant interaction (P = 0.08), as the BCAA group improved
in this measure by 11 % pre- to post-study, though this
was not significant (P = 0.15). There was a tendency for
the BCAA group to present a greater post-study serum
BCAA: l-Tryptophan ratio compared to the PLA group
Abstract We examined if supplementing trained cyclists
(32 ± 2 year, 77.8 ± 2.6 kg, and 7.4 ± 1.2 year training)
with 12 g/day (6 g/day l-Leucine, 2 g/day l-Isoleucine and
4 g/day l-Valine) of either branched-chain amino acids
(BCAAs, n = 9) or a maltodextrin placebo (PLA, n = 9)
over a 10-week training season affected select body com-
position, performance, and/or immune variables. Before
and after the 10-week study, the following was assessed:
(1) 4-h fasting blood draws; (2) dual X-ray absorptiometry
body composition; (3) Wingate peak power tests; and (4)
4 km time-trials. No group × time interactions existed for
* Michael D. Roberts
Wesley C. Kephart
Taylor D. Wachs
R. Mac Thompson
C. Brooks Mobley
Carlton D. Fox
James R. McDonald
Brian S. Ferguson
Kaelin C. Young
Ben Nie
Jeffrey S. Martin
Joseph M. Company
David D. Pascoe
Robert D. Arnold
Jordan R. Moon
1 School of Kinesiology, Molecular and Applied Sciences
Laboratory, Auburn University, 301 Wire Road, Office 286,
Auburn, AL 36849, USA
2 Wichita State University, Wichita, KS, USA
3 Harrison School of Pharmacy, Auburn University, Auburn,
4 Edward Via College of Osteopathic Medicine, Auburn
Campus, Auburn, AL, USA
5 Endurance Company, LLC, Bloomington, IL, USA
6 MusclePharm Sports Science Institute, Denver, CO, USA
W. C. Kephart et al.
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(P = 0.08). A significant interaction for neutrophil number
existed (P = 0.04), as there was a significant 18 % increase
within the PLA group from the pre- to post-study time point
(P = 0.01). Chronic BCAA supplementation improves
sprint performance variables in endurance cyclists. Addi-
tionally, given that BCAA supplementation blunted the neu-
trophil response to intense cycling training, BCAAs may
benefit immune function during a prolonged cycling season.
Keywords Leucine · Isoleucine · Valine · Cycling · Peak
power · Immunity
There is substantial interest in nutritional supplementation
in the endurance cycling world to enhance performance
(Tokish et al. 2004) and/or immune function (Gleeson
2007) due to long seasons and high volume training. Con-
cerning endurance activities, branched-chain amino acid
(BCAA) supplementation has been of intense research
interest given the ability of BCAAs to support muscle
mass gains (Blomstrand et al. 2006), reduce catabolism
(Greer et al. 2007), potentially mitigate central fatigue
(Newsholme and Blomstrand 2006), and modulate immune
function (Bassit et al. 2002). BCAAs are comprised of
l-Leucine, l-Isoleucine and l-Valine, and are a triad of
essential amino acids that, when ingested, have potent ana-
bolic/anti-catabolic properties (Gleeson 2005). The current
body of literature views BCAAs, especially l-Leucine, to
be key mediators in activation of muscle protein synthesis
(Anthony et al. 2001). Exercise, particularly moderate and
intense endurance activities, increases energy expenditure
as well as up-regulating catabolism of muscle proteins
(Shimomura et al. 2004). Since BCAAs can be oxidized in
muscle tissue, they are a primary nutrient of interest when
endurance exercise is utilized (van Hall et al. 1996). Oxida-
tion of BCAA breakdown transpires in the mitochondria,
as transamination occurs to produce branched-chain α-keto
acids then is broken down by branched-chain aminotrans-
ferase, subsequently decarboxylation to produce coen-
zyme A compounds, then catalyzed by the branched-chain
α-keto acid dehydrogenase complex (Shimomura et al.
2004). Furthermore, given that BCAA oxidation is consid-
erably up-regulated by strenuous aerobic efforts (Gibala
2007; Layman 2002; Rennie and Tipton 2000; Shimomura
et al. 2004), BCAA supplementation either pre- or post-
exercise may be able to circumvent some of the catabolic
effects attained from strenuous endurance activities, due
to increased circulating BCAAs thereby not necessitating
Research conducted in animal models has shown
that acute BCAA supplementation increases endurance
performance compared to a placebo and/or glucose blend,
respectively (Calders et al. 1997, 1999). Previous human
studies indicate that BCAAs supplemented (77 mg/kg
body weight) prior to exercise resulted in greater muscle
ammonia production, intracellular and arterial BCAA lev-
els along with reducing endogenous muscle breakdown
(MacLean et al. 1994). Other acute studies have shown that
low doses (2.5 g) of BCAAs to elicit lower levels of per-
ceived muscle soreness and a greater propensity for knee
flexion torque in subsequent days (24 and 48 h) follow-
ing a 3–90 min bouts of submaximal cycling (Greer et al.
2007). However, BCAAs ingested prior to performance of
a 100 km time-trial have been shown to acutely have no
effect in well trained cyclists, when added with glucose
(Madsen et al. 1996). These outcomes have been similar for
running performance (Newsholme et al. 1991).
Regarding longer-term supplementation paradigms, a
previous investigation has found that BCAA supplementa-
tion at 12 g/day for 2 weeks along with an additional 20 g
each prior to and following a single 120 min bout of endur-
ance cycling has been associated with decreased serum
creatine kinase and lactate dehydrogenase, suggesting that
BCAA reduces muscle damage concomitant with endur-
ance exercise as well as possibly having lingering effects
on lower levels of intramuscular catabolism in the days
following exertion (Coombes and McNaughton 2000).
Furthermore, Crowe et al. (2006) reported that 6 weeks of
l-Leucine supplementation (45 mg/kg bodyweight/day)
led to greater power outputs delayed time to fatigue during
a sprinting trial in outrigger canoeists. Null findings with
acute BCAA supplementation prior to an exercise bout ver-
sus the positive findings after chronic supplementation may
suggest that, like creatine monohydrate supplementation,
there is a potential need for tissue BCAA ‘saturation’ to
occur in order to experience ergogenic effects.
Notwithstanding, performance benefits of chronic
BCAA supplementation, especially with well-trained
cyclists, is sparse. Likewise, little current research speaks
to outcomes of chronic BCAA supplementation regarding
endurance cycling performance with continued supple-
mentation over a training season. Thus, the purpose of this
study is to investigate the chronic effects of BCAA supple-
mentation on markers of endurance cycling performance
throughout the duration of a 10-week training season.
Upon approval from the Auburn University Institutional
Review Board, participants read and signed Informed Con-
sent, prior to study participation. Inclusion criteria were
Ten weeks of branched-chain amino acid supplementation improves select performance and…
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absences of precluding injuries that would inhibit cycling
performance, males between ages of 18 and 55 years old,
as well as a minimum of 1 year of cycling experience. Of
the 18 participants who completed the study, 17 were road
cyclists with the other remaining participant being pre-
dominantly focused on mountain bike riding, while of a
subtly different modality, was not an outlier in dependent
Participants arrived at the laboratory and filled out pre-
exercise questionnaires regarding health, exercise readi-
ness, and cycling history. After this, participants were fit-
ted to a Velotron Dynafit pro cycle ergometer (Racermate,
Inc. Seattle, WA, USA) and were allowed to pedal at a low
intensity to determine the best fit. Participants then per-
formed a 30 s Wingate maximal anaerobic test which con-
sisted of 20 s of light pedaling followed by a 5 s accelera-
tion phase, then a 30 s maximal effort where the flywheel
resistance was set at 9 % of the participants’ body mass.
Data derived from the Wingate test were peak/mean power
and relative peak/mean power. Of note, participants were
allowed to use their personal biking shoes and pedals in
order to clip into the crank arms of the cycle ergometer.
Following a cool-down (unloading pedaling for 3–5 min
depending on participant desire), participants had a 10 min
break before completing a 4 km time-trial. The 4 km time-
trial, utilized as a surrogate for endurance performance,
was performed using the participant’s road bike which was
attached to a Computrainer (Racermate, Inc. Seattle, WA,
USA) to adjust cycling resistance with a magnetic braking
apparatus (Abbiss and Laursen 2005; Ansley et al. 2004).
The participant’s road bike was outfitted with a rear-wheel
hub CycleOps power meter (Madison, WI, USA) which
was synchronized to a handheld Garmin device (Garmin
Edge 500, Olathe, KS, USA) in order to measure power
output. The researcher then had the participant pedal at a
self-selected cadence and magnetic brake resistance in
which he would be comfortable completing the 4-km time-
trial. This brake resistance was apparent to the tester but
not the rider. The rider then performed the familiarization
4 km time-trial as quickly as possible. Data derived from
this were 4 km time-trial time and average power over that
time. If the resistance became too cumbersome then the
participant was allowed to downshift in order to complete
the time-trial; of note, if the participant down-shifted while
maintaining a similar cadence then speed and power output
decreased. Essentially, the participants were instructed to
complete the trial as fast as possible and were permitted to
change the brakeweight as necessary. In this manner, time
to completion was obtained once the rider reached 4 km on
the stationary trainer computer, and 4 km average power
output was recorded from the Garmin bike computer. After
completion of the 4 km time-trial, the participants then
scheduled a time for pre-testing measures to begin which
occurred approximately 1 week later.
Pre‑ and post‑testing procedures as well
as supplementation procedures
Participants came into the laboratory following a 4 h
abstaining period from food and/or caffeine. Venous blood
samples were drawn from an antecubital vein of partici-
pants, and placed into a 5 mL serum separator tube and
3 mL EDTA tube (BD Vacutainer, Franklin Lakes, NJ,
USA) for subsequent analysis serum and whole blood
analysis, respectively. Participants were then given a stand-
ardized cereal bar (2 g protein, 24 g carbohydrates, 3 g
fat, 120 kcal) in order to prevent potential hypoglycemic
events during cycling testing. Hydration status of partici-
pants was then measured by urine testing via a handheld
refractometer (ATAGO 2393, Bellevue, WA, USA). The
hydration cut off for testing was determined using a urine-
specific gravity value of 1.020 g mL1. If participants pro-
duced a higher value than the aforementioned one then
0.5 L of water was required to be consumed before testing
procedures could continue. Each participant then under-
went a dual-energy X-ray absorptiometry (DEXA) scan
on a Lunar Prodigy (GE Corporation, Fairfield, Connecti-
cut, USA) in order to determine total body fat mass, total
body lean mass, and dual leg lean mass. Doing in-house
laboratory testing, the same-day reliability of the DEXA
during a test-calibrate-retest on 10 participants produced
intra-class correlation coefficients of 0.998 for total body
fat mass [mean difference between tests (mean ± stand-
ard error) = 0.40 ± 0.05 kg], 0.998 for total body lean
mass [mean difference between tests (mean ± stand-
ard error) = 0.29 ± 0.13 kg], and 0.998 for dual-leg lean
mass [mean difference between tests (mean ± standard
error) = 0.17 ± 0.09 kg].
Subsequent cycling testing mimicked the familiari-
zation trial. Specifically, a Wingate test was performed
as described above, and this was followed by the 4 km
time-trial described above. Following cycling testing,
participants were assigned into groups (based on study
entry order), in a double blind manner. One group was
instructed to consume supplement ‘A’ (12 g of BCAAs:
BCAA 3.1.2; MusclePharm Corp., Denver, CO, USA) in
capsule form (16 total capsules per day) for 10 weeks. Of
the 12 g of BCAAs, 6 g = l-Leucine, 2 g = l-Isoleucine
and 4 g = l-Valine. The second group was instructed to
consume supplement ‘B’ (12 g of maltodextrin placebo,
PLA; 16 total capsules per day) for 10 weeks. Further-
more, participants were instructed to consume 8 capsules
on an empty (2 h post-prandial) stomach and eight capsules
W. C. Kephart et al.
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following exercise sessions on training days. On non-train-
ing days, participants were instructed to consume eight
capsules twice daily on an empty stomach.
Participants were instructed to maintain normal dietary
habits over the duration of the investigation. Moreover, the
participants were instructed to obtain at least 160 km (100
mi) of riding per week and were instructed to log their rid-
ing volume on a daily basis. E-mail contact was maintained
with the participants throughout the duration of the investi-
gation to ensure that participants did not report any adverse
effects of either BCAAs or PLA and were adhering to the
study. Following the 10-week supplementation and train-
ing period, post testing procedures were re-performed dur-
ing the same time of day for each participant as described
Whole blood assessment for white blood cell
On the days of blood collection during pre- and post-test-
ing, all 3 mL EDTA tubes were refrigerated upon blood
collection. In the evening, all tubes were transported to
the CLIA certified Auburn University Medical Clinic, and
complete blood count (CBC) panels were analyzed using
Beckman-Coulter DxH 600 Hematology analyzer (Beck-
man Coulter, Fullerton, CA, USA). Specifically, the fol-
lowing parameters were determined: total white blood cells
(WBCs), neutrophils (absolute counts and percentage of
WBCs), lymphocytes (absolute counts and percentage of
WBCs), and monocytes (absolute counts and percentage of
WBCs) were determined.
Serum BCAA and tryptophan analyses
Amino acids used for standards included: l-Leucine (99 %
purity; EMD Millipore, Billerica, MA, USA), l-Isoleucine
(99 % purity; Alfa Aesar, Ward Hill, MA), l-Valine (99 %
purity; Alfa Aesar, Ward Hill, MA) and l-Tryptophan
(99 % purity; Alfa Aesar, Ward Hill, MA), d-Leucine-d10
(99 % purity, CDN isotopes, Pointe-Claire, Quebec, CA),
d-Valine-d8 (99 % purity, CDN isotopes, Pointe-Claire,
Quebec, CA) and d-Tryptophan-d8 (99 % purity, CDN
isotopes, Pointe-Claire, Quebec, CA). Hydrochloric Acid
(HCl, 36–38 %) was purchased from Macron Fine Chemi-
cals, Avantor Performance Materials (Center Valley, PA).
Formic acid (LC–MS grade), acetonitrile (LC–MS grade)
and water (LC–MS grade) were purchased form Sigma-
Aldrich (St. Louis, MO).
Phosphate-buffered saline (PBS) was used for prepara-
tion of stock solutions and standard working solutions.
Amino acid standards were dissolved in PBS to prepare
a stock solution containing l-Leucine (240.0 μg/mL),
l-Isoleucine (203.6 μg/mL), l-Valine (255.0 μg/mL) and
l-Tryptophan (208.0 μg/mL), then the stock solution was
diluted 200-fold in PBS to prepare a working solution. A
serial dilution (1:5) of the standards solution containing all
of the amino acids was prepared. Internal standards were
mixed to prepare a working solution containing d-Leucine-
d10 (1000 ng/mL), d-Valine-d8 (1220 ng/mL) and d-Tryp-
tophan-d8 (1050 ng/mL).
Serum samples (5 μL) were diluted 200-fold to 1.0 ml
in PBS. A 130 μL sample (diluted serum sample, standard
or blank) was added to 100 μL of internal standard solu-
tion. Samples were deproteinated with the addition of 20
μL of HCl to a final volume of 230 μL, vortexed for 30 s
and centrifuged for 20 min at 14,000g. A 100 μL aliquot
of the resultant supernatant was transferred to glass vial
and analyzed by liquid-chromatography tandem mass spec-
trometry (LC–MS/MS).
l-Leucine, l-Isoleucine, l-Valine and l-Tryptophan was
quantified by LC–MS/MS using the internal standards,
d-Leucine-d10 (for l-Leucine and l-Isoleucine), d-Valine-
d8 and d-Tryptophan-d8. Analysis was performed on an
Agilent 1290 UHPLC system coupled Agilent 6460 Tri-
ple Quad mass spectrometer (Agilent Technologies, Santa
Clara, CA 95051, USA). The mobile phase consisted of
0.1 % (v/v) formic acid and acetonitrile. The samples
were separated on ACQUITY UPLC HSS T3 column
(2.1 × 100 mm, 1.8 μm) using a gradient from 2 to 5 %
of acetonitrile for 1 min, then to 30 % for 1 min and kept
at 30 % for 0.5 min. Samples (1 μL injection volume)
were introduced into the mass spectrometer a flow rate of
0.5 mL/min using Agilent Jet Stream™ electrospray ioni-
zation (ESI) source. Nitrogen was used as the drying (10 L/
min at 350 °C), nebulizer (45 psi), and collision gas. Capil-
lary voltage was set at 4000 V. Mass spectra were acquired
in positive-ion mode, and mass transitions were monitored
using multiple-reaction monitoring; Transitions were:
l-Leucine 132.2–86.2, l-Isoleucine 132.2–86.2, l-Valine
118.0-72.1, l-Tryptophan 205.1–188.1, d-Leucine-d10
142.2–96.2, d-Valine-d8 126.1–80.2, d-Tryptophan-d8
213.1–95.1. This method was linear from 1.00 to 1300 ng/
mL for each amino acid with a lower limit of quantification
(LLOQ) of 1.0 pg on column, accuracies 90 %, and coef-
ficient of variation 15 %.
Unless otherwise stated, all data are presented as
mean ± standard error. All statistics were performed using
SPSS v22.0 (Chicago, IL, USA), and an a priori alpha (α)
level to detect significance was set at P 0.05. Participant
demographics between treatment groups (age, km ridden per
week, average km ridden) were compared using independ-
ent t tests. For markers of performance, body composition,
blood counts, and serum amino acids a 2 × 2 (group by time)
Ten weeks of branched-chain amino acid supplementation improves select performance and…
1 3
mixed factorial ANOVA was utilized to derive group × time
interactions. In order to make the results more concise, if
main group effects or main time effects were not significant
or did not approach significance (P > 0.10), then these P
values were not presented in the results section. If a signifi-
cant group × time interactions or main effect for time α was
obtained, subsequent paired samples t tests and independent
t test were applied to locate specific differences, on within-
subject and between-subject variables, respectively. Likewise,
due to the small sample sizes, if a group × time interaction or
main effect for time approached significance (P 0.10), then
‘forced’ post hoc analyses were also explored.
No between‑group differences existed for riding volume
over the study duration
No between-group differences existed for height
(P = 0.33), pre-intervention body mass (P = 0.88), age
(P = 0.98) and years cycling (P = 0.53) (Table 1). Further-
more, following the intervention, no between-group dif-
ferences were found regarding total km ridden (P = 0.29)
and/or average km/week (P = 0.43; Table 1).
BCAA supplementation increases cycling sprint power
without altering body composition
No group × time interactions existed for body fat percent-
age (P = 0.92; Fig. 1a), total fat mass (P = 0.78; Fig. 1b),
total lean mass (P = 0.27; Fig. 1c) or dual-leg lean mass
(P = 0.96; Fig. 1c).
Interestingly, and in spite of total or dual-leg lean mass
not being altered in the between groups, a group × time
interaction was evident for peak power (P = 0.02; Fig. 2a),
relative peak power (normalized to body mass, P = 0.01;
Fig. 2b), and mean power (P = 0.01; Fig. 2c). Further anal-
ysis revealed that the BCAA group increased peak power
by 20 % compared to the pre-study time point (P = 0.01).
The BCAA group also experienced a 19 % increase in rela-
tive peak power (P = 0.01) compared to the pre-study time
Table 1 Participant demographics
Total cycling (km) was the total distance logged by participants over the 10-week study. Average cycling was the average distance per week
logged over the 10-week study
BCAA branched-chain amino acid group, PLA placebo group
Group Number of
Pre mass (kg) Height (cm) Age (years) Training age (years) Total cycling (km) Average cycling
BCAA 9 78.2 ± 3.9 172 ± 8 32.1 ± 2.9 8.2 ± 2.0 1861 ± 182 192 ± 20
PLA 9 77.4 ± 3.6 170 ± 8 32.2 ± 3.3 6.6 ± 1.7 2120 ± 150 212 ± 15
Fig. 1 Pre- and post-study
body composition variables.
Pre-study (pre) and 10-week
post-study (post) body composi-
tion variables. No group *time
interactions were observed for
body fat percentage (panel a),
body fat mass (panel b), total
lean body mass (LBM; panel c),
or dual leg LBM (panel d)
18.4 18.8
18.4 18.9
Pre Post
Body Fat (%)
BCAA Placebo
13.9 14.3
14.2 14.4
Pre Post
Body Fat (kg)
23.5 23.7
23.0 23.2
Pre Post
Dual-leg LBM (kg)
61.3 61.3
60.5 59.8
Pre Post
Total LBM (kg)
(a) (b)
W. C. Kephart et al.
1 3
point. In addition, the BCAA group experienced a 4 %
increase in mean power (P = 0.01) compared to the pre-
study time point. A group × time interaction failed to reach
significance for relative mean power (P = 0.35; Fig. 2d).
Time to complete the 4 km time-trial approached a
group × time interaction (P = 0.08; Fig. 3a). Further analysis
revealed that the BCAA group improved on the 4 km time-
trial to completion by 11 %, though this was not statistically
significant (P = 0.15). Group × time interactions failed to
reach significance for 4 km time-trial power and 4 k time-trial
power/kg (P = 0.26, P = 0.28; Fig. 3b, c, respectively).
BCAA supplementation does not significantly alter
fasting serum amino acids
Given that chronic BCAA supplementation increased peak
and mean Wingate power in cyclists without increasing
dual-leg lean tissue mass (i.e., an increase in power with-
out an increase in hypertrophy), we were next interested
in examining if there were between-group differences
in fasting serum BCAAs, l-Tryptophan, and the BCAA:
l-tryptophan ratio given that these variables are all related
to the proposed central fatigue hypothesis (i.e., offsetting
serum l-Tryptophan with BCAAs may allow more BCAAs
to cross the blood–brain barrier which can enhance work
output by reducing central fatigue) (Blomstrand 2001;
Davis et al. 2000). No significant group × time interaction
for serum BCAAs (P = 0.13; Fig. 4a) serum l-tryptophan
(P = 0.82; Fig. 4b) or serum BCAAs: l-Tryptophan ratio
(P = 0.22; Fig. 4c). Interestingly, there was a main effect
for time regarding serum l-Tryptophan, whereby collaps-
ing the mean of both groups over time revealed an increase
in this circulating marker after the 10 week cycling inter-
vention (P = 0.05); however, there were no within-group
increases. A main effect for time also came near to statis-
tical significance regarding serum BCAA: l-Tryptophan
ratio, whereby collapsing the mean of both groups over
time tended to decrease this measure after the 10-week
cycling intervention (P = 0.10). Upon further post hoc
analysis, there was a tendency for the BCAA group to pre-
sent a greater post-study serum BCAA: l-Tryptophan ratio
compared to the PLA group (P = 0.08).
BCAA supplementation blunts neutrophil increases
in cyclists
Finally, we were interested in examining whether chronic
BCAA supplementation affected whole blood immune mark-
ers given that: (1) rigorous endurance training can lead to
increases in circulating neutrophils and decreases in circulating
1,212 1,251
Pre Post
Peak Power (Watts)
BCAA Placebo
699 726
756 740
Pre Post
Mean Power (Watts
15.6 16.2
Pre Post
Relative PP (Watts/kg)
9.0 9.3
9.8 9.6
Pre Post
Relative MP (Watts/kg)
(a) (b)
(c) (d)
Fig. 2 Effects of chronic BCAA supplementation on Wingate vari-
ables in cyclists. Pre-study (pre) and 10-week post-study (post) Win-
gate variables. A group × time interaction was observed for peak
power (P = 0.02), and the BCAA group increased peak power by
20 % compared to the pre-study time point (**P = 0.01) (panel a).
A group × time interaction was also observed for relative peak power
(P = 0.01), and the BCAA group increased relative peak power by
19 % compared to the pre-study time point (**P = 0.01) (panel b).
A group × time interaction was observed for mean power (P = 0.01),
and the BCAA group increased mean power by 4 % compared to the
pre-study time point (**P = 0.01) (panel c). No group × time inter-
actions was observed for relative mean power (MP; panel d)
Ten weeks of branched-chain amino acid supplementation improves select performance and…
1 3
lymphocytes which, in turn, can lead to an immunocom-
promised state (Pedersen et al. 1997); and (2) BCAAs have
been shown to be a viable energy for immune cells (Calder
2006). No group × time interaction existed for WBC counts
(P = 0.24; Fig. 5a). Interestingly, a group × time interaction
approached significance for percent neutrophils (P = 0.06;
Fig. 5b) and a group × time interaction was significant for
neutrophil number (P = 0.04; Fig. 5c). Regarding neutrophil
percentages, post hoc analysis revealed a 4.6 % increase in the
PLA group over time (P = 0.01), and a between group differ-
ence existed at the post-study time point (P = 0.05). Regard-
ing neutrophil number, there was a significant 18 % increase
within the PLA group from the pre- to post-study time points
(P = 0.01), as well as a suggestive tendency between groups
at the post-study time point (P = 0.07). There was also a ten-
dency toward a group × time interactions for lymphocyte
percentages (P = 0.11; Fig. 5d), but not lymphocyte numbers
(P = 0.69; Fig. 5e). Monocyte percentages reached a signifi-
cant group × time interaction (P = 0.05; Fig. 5f), but there
were no significant differences when post hoc analysis was
conducted. There was no significant group × time interaction
for monocyte numbers (P = 0.19; Fig. 5g).
Presently there is a lack of literature concerning chronic
amino acid supplementation and subsequent alterations in
6.6 6.1
5.9 6.0
Pre Post
4 km TT Time (Min)
BCAA Placebo
263 280
288 287
Pre Post
4 km TT Power (Watts)
3.4 3.6
3.8 3.8
Pre Post
4 km TT Rel. Power (Watts/kg)
(a) (b) (c)
Fig. 3 Effects of chronic BCAA supplementation on 4 km time-trial
measures in cyclists. Pre-study (pre) and 10-week post-study (post)
4 km time-trial measures. No significant group × time interactions
were observed for 4 km time-trial (TT) time to completion (panel a),
4 km TT power (panel b) or 4 km TT relative power (panel c)
Pre Post
Serum BCAA: L-Tryptophan rati
71.8 64.4
Pre Post
Serum BCAAs (µg/µl)
BCAA Placebo
Pre Post
Serum L-Tryptophan (µg/µl)
(a) (b) (c)
Fig. 4 Effects of chronic BCAA supplementation on fasting serum
amino acids in cyclists. Pre-study (pre) and 10-week post-study (post)
fasting serum amino acid analyses. No significant group × time
interactions were observed for serum BCAAs (panel a), serum
l-Tryptophan (panel b) or the serum BCAA: l-Tryptophan ratio
(panel c). There was a main time effect for serum l-Tryptophan to
increase from the pre- to post-study time point when both group
means were collapsed over time (P < 0.05). Likewise, there was a
tendency for the serum BCAA: l-Tryptophan levels to decrease from
the pre- to post-study time point when both group means were col-
lapsed over time, and there was a tendency for this value to be greater
in the BCAA group versus PLA group at the post-study time point
(P = 0.08)
W. C. Kephart et al.
1 3
performance variables in experienced endurance athletes.
In this regard, this is the first study to our knowledge to
investigate the how chronic BCAA supplementation affects
anaerobic and aerobic variables in trained endurance
cyclists. Overall, the major findings of this study are that
chronic BCAA supplementation improves anaerobic meas-
ures associated with cycling sprint performance; specifi-
cally, Wingate performance measures which were signifi-
cantly augmented only in the group ingesting 12 g BCAAs
per day. Moreover, while fasting serum l-Tryptophan ratios
increased with 10 weeks of cycling independent of treat-
ment, chronic BCAA supplementation tended to prevent
a further post-study decrease in fasting serum BCAA:
l-Tryptophan ratio; a finding which may link BCAA sup-
plementation to the aforementioned increase in perfor-
mance variables. A secondary but noteworthy finding from
this investigation was a blunting of elevated neutrophil
values with chronic BCAA supplementation. Collectively,
these findings are discussed in greater detail below.
BCAA supplementation enhances power output
in cyclists
Echoing previous literature, our findings support that
chronic BCAA supplementation increases anaerobic power
capacity, although we did not observe an increase in total
body and/or dual-leg lean mass. As mentioned previously,
Crowe et al. (2006) have shown that l-Leucine supplemen-
tation over 6 weeks enhanced power performance in trained
canoeists. Thus, our findings are in agreement with those
reported by Crowe et al. in that chronic BCAA ingestion
seems to enhance short-term power output in experienced
athletes. Moreover, the current data as well as the data
reported by Crowe et al. collectively suggest that BCAA
supplementation may enhance power output across vary-
ing exercise modalities; that is to say that the benefits from
BCAAs are not allocated to specific joints, muscles and/or
types of movements. However, Crowe et al. did not assess
changes in lean tissue mass in these athletes, so we cannot
compare our null body composition findings to their find-
ings in this regard.
Other investigations have illustrated that both acute and
chronic BCAA supplementation protocols can enhance
muscle functionality in the absence of hypertrophy. For
instance, it has been reported that humans supplementing
with BCAAs over 30 days experienced increases in fore-
arm grip strength without concomitantly increasing skel-
etal muscle mass (De Lorenzo et al. 2003). Howatson et al.
(2012) also reported that maximal voluntary contraction
(MVC) was dampened after a muscle damaging exercise
50 47
51 55
Pre Post
Neutrophils (% WBCs)
39 41
36 33
Pre Post
Lymphocytes (% WBCs)
7.3 8.3
9.1 8.3
Pre Post
Monocytes (% WBCs)
3.3 3.1
Pre Post
Neutrophils (1
03 cells/µl)
2.6 2.6
2.4 2.4
Pre Post
Lymphocytes (1
03 cells/µl)
0.6 0.6
Pre Post
Monocytes (1
03 cells/µl)
6.6 6.5
Pre Post
White blood cells (103 cells/µl)
BCAA Placebo
(a) (b)
Fig. 5 Effects of chronic BCAA supplementation on immune vari-
ables in cyclists. Pre-study (pre) and 10-week post-study (post)
immune variables. No significant group × time interactions was
observed for while blood cell counts (panel a). A group × time inter-
action trend was observed for neutrophil percentages (P = 0.06;
panel b). A group × time interaction existed for neutrophil number
(P = 0.04), and there was an 18 % increase within the PLA group
from the pre- to post-study time points (**P = 0.01) (panel c). No
significant group*time interactions were observed for lymphocyte
percentages and counts (panels d, e) or monocyte percentages and
counts (panels f, g). Other symbols: between-group difference at a
given time point (P < 0.05)
Ten weeks of branched-chain amino acid supplementation improves select performance and…
1 3
bout in humans, though short-term BCAA supplementation
was better able to preserve this post-bout decrease in MVC
up to 96 h post-exercise, compared to placebo. Collectively,
the results presented herein as well as the aforementioned
literature suggests that BCAA supplementation enhances
short-term powerful efforts without affecting muscle mass.
Interestingly, chronic BCAA supplementation did not
enhance 4 km time-trial time or 4 km time-trial power;
both variables which are considered to be more endurance-
associated compared to the Wingate test, given that the
4 km time-trial took ~6 min to complete and the Wingate
took 30 s. Acute BCAA ingestion protocols have yielded
similar results. For instance, Madsen et al. (1996) demon-
strated that the acute ingestion of BCAAs + glucose did
not improve 100 km time to exhaustion when compared
to a glucose only and non-caloric placebo trials, despite
increases in plasma BCAA levels during the cycling bout
in the BCAA-supplemented group. Watson et al. (2004)
replicated these findings, reporting that the acute ingestion
of BCAAs did not improve cycling to exhaustion in glyco-
gen-depleted subjects that exercised in a warm environment
despite increases in plasma BCAAs. It should be noted that
the 4 km cycling time trial employed herein was not nearly
as ‘aerobically oriented’ compared to the 100 km time tri-
als reported above and, thus, comparisons between data
are limited. However, Toone and Betts (2010) have shown
that including a BCAA-rich protein source with carbohy-
drates increased/worsened a 6 km time to completion by
6 % in competitive cyclists. Davis et al. (1999) also dem-
onstrated that acute BCAA ingestion in conjunction with
carbohydrates had no effect on endurance performance
(shuttle-run) compared to carbohydrates alone. Finally,
while animal models suggest that BCAAs may confer acute
benefits to endurance performance (Calders et al. 1997,
1999), equivocal data also exist (Davis et al. 1999). Thus,
it appears that acute and/or chronic BCAA supplementa-
tion, while enhancing power-associated variables, does not
improve endurance performance variables. As it appears to
be well established that acute BCAA ingest does not aid
in endurance performance, the novel aspect of this investi-
gation indicates that chronic BCAA supplementation does
not seem to be efficacious in enhancing select endurance
Finally, it is noteworthy to mention that, while chronic
BCAA supplementation did not statistically increase fast-
ing serum BCAA levels, it did tend to elevate the serum
BCAA: l-Tryptophan ratio after the 10-week interven-
tion compared to the PLA group. Central fatigue has been
posited to arise from higher circulating levels of l-Tryp-
tophan traversing the blood brain barrier and being con-
verted into serotonin; this ultimately being linked to fatigue
(Blomstrand 2001; Davis et al. 2000). Research focus-
ing on performance outcomes has shown that ingestion
of carbohydrates can favorably alter the BCAA: l-Tryp-
tophan ratio and is linked to better time until exhaustion
performance (Davis et al. 1992). Theoretically, given that
BCAAs can also cross the blood–brain barrier, chronic
BCAA supplementation with the intent of habitually dis-
rupting the brain production of serotonin may also mitigate
central fatigue (Blomstrand 2001). In light of the fact that
we observed increases in anaerobic performance variables
without increases in dual-leg lean mass, as well as a ten-
dency for serum BCAA: l-Tryptophan ratios to be favora-
ble altered, we posit that performance enhancement with
chronic BCAA supplementation could be related to a cen-
tral fatigue-mediated mechanism. However, this hypothesis
is limited given that we did not use a mechanistic approach
to decipher if preserved serum BCAA: l-Tryptophan ratios,
and possible brain BCAA: l-Tryptophan ratios and/or sero-
tonin levels were predictive of performance. To this end,
more mechanistic animal models are needed in order to
determine if chronic BCAA supplementation offsets brain
serotonin production and whether this is associated with
increases in anaerobic performance variables.
BCAA supplementation blunts neutrophil increases
in cyclists
Intense exercise induces neutrophil proliferation (Peake
2002; Suzuki et al. 1996), and repetitive cycling bouts have
been shown to increase neutrophilia and alter neutrophil
function (Suzuki et al. 1999). Exercise-induced alterations
in neutrophil number and/or function may be a maladap-
tive response, which can lead to a compromised immune
function (Nieman 1997). Herein, we report an increase in
neutrophil counts in PLA group from the pre- to post-study
time point; an effect which may be due to altered neutro-
phil function. It has been posited that BCAAs are essential
for lymphocyte and neutrophil function given that protein
synthetic rates in these cells are driven by BCAAs (Cal-
der 2006). BCAAs have also been shown to: (1) enhance
neutrophil function by increasing phagocytotic capacity
(Nakamura et al. 2007); and (2) enhance the ability of other
immune cell types (lymphocytes, monocytes and mac-
rophages) to proliferate in vitro in response to cytokines
after a 30 km run (Bassit et al. 2002). Hence, with chronic
BCAA supplementation, there may not be an impetus for
up-regulating neutrophil counts due to an enhancement
in neutrophil function. Currently we cannot support these
findings outright as that was not a primary concern of this
investigation, and specific cellular mechanics were not
measured. However, our data supports chronic BCAA sup-
plementation reduces the increase in neutrophil counts that
occur with 10 weeks of high volume cycling, and this may
favor an enhancement in immune function. In this regard,
more mechanistic studies are warranted with regards to
W. C. Kephart et al.
1 3
how BCAAs affect immune cell function over chronic
training interventions in endurance athletes.
This is the first study to our knowledge to explore the
effects of chronic BCAA supplementation with regard
to changes in performance variables relevant to endur-
ance cyclists. Limitations to the current study include:
(1) a relatively small sample size of cyclists, (2) the lack
of sampling at intermittent time points (i.e., 2, 4 weeks,
etc.), and (3) the lack of more mechanistic immune cell
data to explain why neutrophil alterations occurred with
BCAA supplementation. Furthermore, while participants
were instructed to consume 8 capsules twice per day
on an empty stomach, this paradigm is not ‘consumer
friendly’, as many ‘real-world’ participants likely opt
to consume BCAAs in powder form and/or with meals.
Notwithstanding, this study illustrates that chronic
BCAA supplementation improves sprint performance
variables in well-trained road cyclists, particularly mean/
peak power and relative mean/peak power but not time
for a 4 km completion. Moreover, the alterations in cir-
culating BCAA: l-Tryptophan ratios may be responsible
for some of the performance benefits. BCAAs may also
benefit immune function during a prolonged cycling sea-
son, although more research is needed to expand upon
our findings.
Acknowledgments The authors thank the participants for devoting
time to this study. Reagent costs and participant compensation costs
were paid through a contract awarded to M.D.R. through MuscleP-
harm Corp. (Denver, CO). B.N. and R.D.A were supported in part by
funding from NIH R01 EB016100.
Compliance with ethical standards
Besides J.R.M., none of the authors have conflicts of interest. J.R.M.
is a Ph.D. scientist employed by the MusclePharm Research Insti-
tute, but he substantially contributed to the study design and data
write-up. Therefore, all co-authors agreed that his work into this
project warranted co-authorship. It should also be noted that all par-
ticipants gave their informed consent in writing prior to inclusion in
the study. Identifying details (names, dates of birth, identity num-
bers and other information) of the participants are not published in
the current work.
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Full-text available
Background It is well documented that exercise-induced muscle damage (EIMD) decreases muscle function and causes soreness and discomfort. Branched-chain amino acid (BCAA) supplementation has been shown to increase protein synthesis and decrease muscle protein breakdown, however, the effects of BCAAs on recovery from damaging resistance training are unclear. Therefore, the aim of this study was to examine the effects of a BCAA supplementation on markers of muscle damage elicited via a sport specific bout of damaging exercise in trained volunteers. Methods Twelve males (mean ± SD age, 23 ± 2 y; stature, 178.3 ± 3.6 cm and body mass, 79.6 ± 8.4 kg) were randomly assigned to a supplement (n = 6) or placebo (n = 6) group. The damaging exercise consisted of 100 consecutive drop-jumps. Creatine kinase (CK), maximal voluntary contraction (MVC), muscle soreness (DOMS), vertical jump (VJ), thigh circumference (TC) and calf circumference (CC) were measured as markers of muscle damage. All variables were measured immediately before the damaging exercise and at 24, 48, 72 and 96 h post-exercise. Results A significant time effect was seen for all variables. There were significant group effects showing a reduction in CK efflux and muscle soreness in the BCAA group compared to the placebo (P<0.05). Furthermore, the recovery of MVC was greater in the BCAA group (P<0.05). The VJ, TC and CC were not different between groups. Conclusion The present study has shown that BCAA administered before and following damaging resistance exercise reduces indices of muscle damage and accelerates recovery in resistance-trained males. It seems likely that BCAA provided greater bioavailablity of substrate to improve protein synthesis and thereby the extent of secondary muscle damage associated with strenuous resistance exercise. Clinical Trial Registration Number: NCT01529281.
Full-text available
This study was designed to compare the effects of energy-matched carbohydrate (CHO) and carbohydrate-protein (CHO-PRO) supplements on cycling time-trial performance. Twelve competitive male cyclists and triathletes each completed 2 trials in a randomized and counterbalanced order that were separated by 5-10 d and applied in a double-blind manner. Participants performed a 45-min variable-intensity exercise protocol on a cycle ergometer while ingesting either a 9% CHO solution or a mixture of 6.8% CHO plus 2.2% protein in volumes providing 22 kJ/kg body mass. Participants were then asked to cycle 6 km in the shortest time possible. Blood glucose and lactate concentrations were measured every 15 min during exercise, along with measures of substrate oxidation via indirect calorimetry, heart rate, and ratings of perceived exertion. Mean time to complete the 6-km time trial was 433 + or - 21 s in CHO trials and 438 + or - 22 s in CHO-PRO trials, which represents a 0.94% (CI: 0.01, 1.86) decrement in performance with the inclusion of protein (p = .048). However, no other variable measured in this study was significantly different between trials. Reducing the quantity of CHO included in a supplement and replacing it with protein may not represent an effective nutritional strategy when the supplement is ingested during exercise. This may reflect the central ergogenic influence of exogenous CHO during such activity.
Full-text available
In this study, five men exercised the knee extensor muscles of one leg for 60 min (71 +/- 2% maximal work capacity) with and without (control) an oral supplement (77 mg/kg) of branched-chain amino acids (BCAA). BCAA supplementation resulted in a doubling (P < 0.05) of the arterial BCAA levels before exercise (339 +/- 15 vs. 822 +/- 86 microM). During the 60 min of exercise, the total release of BCAA was 68 +/- 93 vs. 816 +/- 198 mumol/kg (P < 0.05) for the BCAA and control trials, respectively. The intramuscular BCAA concentrations were higher (P < 0.05) for the BCAA trial and remained higher (P < 0.05) throughout exercise. In both trials, substantial quantities of NH3 were released, and when NH3 production equivalent to IMP accumulation was subtracted the net NH3 production was 1,112 +/- 279 and 1,670 +/- 245 mumol/kg (P < 0.05) for the control and BCAA trials, respectively. In contrast, the release of the essential amino acids (EAA) was much lower for the BCAA than the control trial (P < 0.05). When the BCAA were subtracted from the EAA (EAA-BCAA), the total release of EAA minus BCAA was lower (P < 0.05) for the BCAA (531 +/- 70 mumol/kg) than the control (924 +/- 148 mumol/kg) trial. These data suggest that BCAA supplementation results in significantly greater muscle NH3 production during exercise. Furthermore, the increased intramuscular and arterial BCAA levels before and during exercise result in a suppression of endogenous muscle protein breakdown during exercise.
Brain serotonin (5-hydroxytryptamine, 5-HT) has been suggested to be involved in central fatigue during prolonged exercise. Changes in the ratio of plasma free tryptophan (free Trp) to branched-chain amino acids (BCAA) are associated with altered brain 5-HT synthesis. The purposes of this study were to describe systematically the effects of prolonged exercise on changes in plasma free Trp and BCAA and to examine the effects of carbohydrate (CHO) feedings on these same variables. Eight well-trained men [\(\dot V{\text{O}}_{\text{2}} \) max = 57.8 (SE 4.1) ml kg−1 min−1] cycled for up to 255 min at a power output corresponding toVO2 at lactate threshold (approximately 68%VO2max) on three occasions separated by at least 1 week. Subjects drank 5 ml kg−1 body wt−1 of either a water placebo, or a liquid beverage containing a moderate (6% CHO) or high (12% CHO) concentration of carbohydrate beginning at min 14 of exercise and every 30 min thereafter. Exercise time to fatigue was shorter in subjects receiving placebo [190 (SE 4) min] as compared to 6% CHO [235 (SE 10) min] and 12% CHO [234 (SE 9) min] (P<0.05). Glucose and insulin decreased in the placebo group, and free Trp, free-Trp/BCAA, and free fatty acids increased approximately five- to sevenfold (P < 0.05). These changes were attenuated in a dose-related manner by the carbohydrate drinks. Plasma free Trp and plasma free fatty acids were highly correlated (r=0.86,P<0.001). Plasma BCAA did not change in the placebo group, but decreased slightly in those receiving 6% CHO and 12% CHO (P<0.05). No differences in heart rate,\(\dot V{\text{O}}_{\text{2}} \), plasma volume and respiratory exchange ratio were found. The results indicate that free Trp and free Trp/BCAA increase progressively during prolonged cycling to fatigue. This response was attenuated by CHO feedings. Changes in plasma free fatty acids probably play a prominent role in these responses.
1. Exercise leads to activation (dephosphorylation) of the branched-chain alpha-keto acid dehydrogenase (BCKADH). Here we investigate the effect of low pre-exercise muscle glycogen content and of branched-chain amino acid (BCAA) ingestion on the activity of BCKADH at rest and after 90 min of one-leg knee-extensor exercise at 65% maximal one-leg power output in five subjects. 2. Pre-exercise BCAA ingestion (308 mg BCAAs (kg body wt)-1) caused an increased muscle BCAA uptake, a higher intramuscular BCAA concentration and activation of BCKADH both at rest (9 +/- 1 versus 25 +/- 5% for the control and BCAA test, respectively) and after exercise (27 +/- 4 versus 54 +/- 7%). 3. At rest the percentage active BCKADH was not different, 6 +/- 2% versus 5 +/- 1%, in the normal and low glycogen content leg (392 +/- 21 and 147 +/- 34 mumol glycosyl units (g dry muscle)-1, respectively). The post-exercise BCKADH activity was higher in the low (46 +/- 2%) than in the normal glycogen content leg (26 +/- 2%). 4. It is concluded that: (1) the mechanism of activation by BCAA ingestion probably involves an increase of the muscle BCAA concentration; (2) BCKADH activation caused by exercise and BCAA ingestion are additive; (3) low pre-exercise muscle glycogen content augments the exercise-induced BCKADH activation without an increase in muscle BCAA concentration; and (4) the mechanism of BCKADH activation via BCAA ingestion and low muscle glycogen content are different.
To investigate the cause of disagreement within the large body of literature concerning the effect of exercise on the capacity of circulating neutrophils to produce reactive oxygen species (ROS), 10 male endurance-trained athletes underwent maximal exercise. The generation of superoxide radical (O2-.) by neutrophils was first detected on a cell-by-cell basis by using histochemical nitro blue tetrazolium tests performed directly on fresh unseparated blood, which showed that responsive neutrophils under several stimulatory conditions relatively decreased after exercise. Similarly, O2-. detected with bis-N-methylacridinium nitrate (lucigenin)-dependent chemiluminescence (CL) of a fixed number of purified neutrophils on stimulation with opsonized zymosan was decreased slightly after exercise. In contrast, the 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol)-dependent CL response of the neutrophils indicative of the myeloperoxidase (MPO)-mediated formation of highly reactive oxidants was significantly enhanced after exercise. It therefore suggests that the pathway of neutrophil ROS metabolism might be forwarded from the precursor O2-. production to the stages of more reactive oxidant formation due to the facilitation of MPO degranulation. In addition, these phenomena were closely associated with the exercise-induced mobilization of neutrophils from the marginated pool into the circulation, which was mediated by the overshooting of catecholamines during exercise. These findings indicate that the use of different techniques for detecting ROS or the different stages of neutrophil ROS metabolism could explain some of the disparate findings of the previous studies.
This study was undertaken to determine the effects of ingesting either glucose (trial G) or glucose plus branched-chain amino acids (BCAA: trial B), compared with placebo (trial P), during prolonged exercise. Nine well-trained cyclists with a maximal oxygen uptake of 63.1 +/- 1.5 ml O2. performed three laboratory trials consisting of 100 km of cycling separated by 7 days between each trial. During these trials, the subjects were encouraged to complete the 100 km as fast as possible on their own bicycles connected to a magnetic brake. No differences in performance times were observed between the three trials (160.1 +/- 4.1, 157.2 +/- 4.5, and 159.8 +/- 3.7 min, respectively). In trial B, plasma BCAA levels increased from 339 +/- 28 microM at rest to 1,026 +/- 62 microM after exercise (P < 0.01). Plasma ammonia concentrations increased during the entire exercise period for all three trials and were significantly higher in trial B compared with trials G and P (P < 0.05). The respiratory exchange ratio was similar in the three trials during the first 90 min of exercise; thereafter, it tended to drop more in trial P than in trials G and B. These data suggest that neither glucose nor glucose plus BCAA ingestion during 100 km of cycling enhance performance in well-trained cyclists.
Acute muscular exercise induces an increased neutrophil count concomitant with recruitment of natural killer (NK), B and T cells to the blood as reflected by an elevation in the total lymphocyte count. Meanwhile, following intense exercise of long duration the lymphocyte count declines, non-MHC-restricted cytotoxicity is suppressed, but the neutrophil concentration increases. In relation to eccentric exercise involving muscle damage, the plasma concentrations of interleukin-1, interleukin-6 and the tumor necrosis factor are elevated. In this review we will propose a model based on the possible roles that stress hormones play a mediating the exercise- related immunological changes: adrenaline and to a lesser degree noradrenaline are responsible for the immediate effects of exercise on lymphocyte subpopulations and cytotoxic activities. The increase in catecholamines and growth hormone mediate the acute effects of exercise on neutrophils, whereas cortisol may be responsible for maintaining lymphopenia and neutrocytosis after exercise of long duration. Lastly, the role of beta-endorphin is less clear, but the cytokine response is closely related to muscle damage and stress hormones do not seem to be directly involved in the elevated cytokine level. Other possible mechanisms of exercise-induced immunomodulation may include the so-called glutamine hypothesis, which is based on the fact that skeletal muscle is an important source of glutamine production and that lymphocytes are dependent on glutamine for optimal growth. Furthermore, physiological changes during exercise, e.g. increased body temperature and decreased oxygen saturation may also in theory contribute to the exercise-induced immunological changes.
This study investigated the effects of pre-exercise branched-chain amino acid (BCAA) administration on blood ammonia levels and on time to exhaustion during treadmill exercise in rats. Adult female Wistar rats were trained on a motor driven treadmill. After a 24-h fast, rats were injected intraperitoneally (i.p.) with 1 mL of placebo or BCAA (30 mg), 5 min before performing 30 min of submaximal exercise (N = 18) or running to exhaustion (N = 12). In both cases, rats were sacrificed immediately following exercise, and blood was collected for the measurement of glucose, nonesterified fatty acid (NEFA), lactic acid, BCAA, ammonia, and free-tryptophan (free-TRP) levels. Control values were obtained from sedentary rats that were subjected to identical treatments and procedures (N = 30). Plasma BCAA levels increased threefold within 5 min after BCAA administration. Mean run time to exhaustion was significantly longer (P < 0.01) after BCAA administration (99 +/- 9 min) compared with placebo (76 +/- 4 min). During exercise, blood ammonia levels were significantly higher (P < 0.01) in the BCAA treated compared with those in the placebo treated rats both in the 30-min exercise bout (113 +/- 25 mumol.L-1 (BCAA) vs 89 +/- 16 mumol.L-1) and following exercise to exhaustion (186 +/- 44 mumol.L-1 (BCAA) vs 123 +/- 19 mumol.L-1). These data demonstrate that BCAA administration in rats results in enhanced endurance performance and an increase in blood ammonia during exercise.