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

Authors:
1 3
DOI 10.1007/s00726-015-2125-8
Amino Acids
ORIGINAL ARTICLE
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
mdr0024@auburn.edu
Wesley C. Kephart
wck0007@auburn.edu
Taylor D. Wachs
tdw0013@auburn.edu
R. Mac Thompson
rmt0010@auburn.edu
C. Brooks Mobley
moblecb@auburn.edu
Carlton D. Fox
cdf0007@auburn.edu
James R. McDonald
jrm0013@auburn.edu
Brian S. Ferguson
bsf0003@auburn.edu
Kaelin C. Young
kaelin.young@wichita.edu
Ben Nie
bzn0004@auburn.edu
Jeffrey S. Martin
jmartin@auburn.vcom.edu
Joseph M. Company
joe@endurancecompany.com
David D. Pascoe
pascodd@auburn.edu
Robert D. Arnold
rda0007@auburn.edu
Jordan R. Moon
jordan@musclepharm.com
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,
AL, USA
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.
1 3
(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
Introduction
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
proteolysis.
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.
Methods
Participants
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…
1 3
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
variables.
Familiarization
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.
1 3
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
above.
Whole blood assessment for white blood cell
differentials
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 %.
Statistics
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.
Results
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
participants
Pre mass (kg) Height (cm) Age (years) Training age (years) Total cycling (km) Average cycling
(km/wk)
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
0.0
10.0
20.0
30.0
Pre Post
Body Fat (%)
BCAA Placebo
13.9 14.3
14.2 14.4
0.0
10.0
20.0
Pre Post
Body Fat (kg)
23.5 23.7
23.0 23.2
0.0
10.0
20.0
30.0
Pre Post
Dual-leg LBM (kg)
61.3 61.3
60.5 59.8
0.0
20.0
40.0
60.0
80.0
Pre Post
Total LBM (kg)
(a) (b)
(c)
(d)
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
1,080
1,292
1,212 1,251
0
500
1,000
1,500
2,000
Pre Post
Peak Power (Watts)
BCAA Placebo
**
699 726
756 740
0
200
400
600
800
1,000
Pre Post
Mean Power (Watts
)
**
13.9
16.5
15.6 16.2
0.0
5.0
10.0
15.0
20.0
Pre Post
Relative PP (Watts/kg)
**
9.0 9.3
9.8 9.6
0.0
5.0
10.0
15.0
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).
Discussion
Presently there is a lack of literature concerning chronic
amino acid supplementation and subsequent alterations in
6.6 6.1
5.9 6.0
0.0
5.0
10.0
Pre Post
4 km TT Time (Min)
BCAA Placebo
263 280
288 287
0
50
100
150
200
250
300
350
Pre Post
4 km TT Power (Watts)
3.4 3.6
3.8 3.8
0.0
1.0
2.0
3.0
4.0
5.0
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)
6.3
5.8
5.6
5.0
0.0
2.0
4.0
6.0
8.0
Pre Post
Serum BCAA: L-Tryptophan rati
o
P=0.08
71.5
81.7
71.8 64.4
0
50
100
150
Pre Post
Serum BCAAs (µg/µl)
BCAA Placebo
11.7
12.8
12.3
13.7
0.0
5.0
10.0
15.0
20.0
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
0
20
40
60
80
Pre Post
Neutrophils (% WBCs)
**
39 41
36 33
0
10
20
30
40
50
Pre Post
Lymphocytes (% WBCs)
7.3 8.3
9.1 8.3
0.0
5.0
10.0
15.0
Pre Post
Monocytes (% WBCs)
3.3 3.1
3.4
4.0
0.0
1.0
2.0
3.0
4.0
5.0
Pre Post
Neutrophils (1
03 cells/µl)
P=0.07
**
2.6 2.6
2.4 2.4
0.0
1.0
2.0
3.0
4.0
Pre Post
Lymphocytes (1
03 cells/µl)
0.5
0.5
0.6 0.6
0.0
0.5
1.0
Pre Post
Monocytes (1
03 cells/µl)
6.6 6.5
6.7
7.2
0.0
2.0
4.0
6.0
8.0
Pre Post
White blood cells (103 cells/µl)
BCAA Placebo
(a) (b)
(c)
(d)
(e)
(f)
(g)
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
variables.
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.
Conclusions
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.
References
Abbiss CR, Laursen PB (2005) Models to explain fatigue during pro-
longed endurance cycling. Sports Med 30(10):865–898
Ansley L et al (2004) Regulation of pacing strategies during succes-
sive 4-km time trials. Med Sci Sports Exerc 36(10):1819–1825
Anthony JC, Anthony TG, Kimball SR, Jefferson LS (2001) Signaling
pathways involved in translational control of protein synthesis in
skeletal muscle by leucine. J Nutr 131:856S–860S
Bassit RA et al (2002) Branched-chain amino acid supplementation
and the immune response of long-distance athletes. Nutrition
18:376–379
Blomstrand E (2001) Amino acids and central fatigue. Amino Acids
20:25–34
Blomstrand E, Eliasson J, Karlsson HK, Kohnke R (2006) Branched-
chain amino acids activate key enzymes in protein synthesis after
physical exercise. J Nutr 136:269S–273S
Calder PC (2006) Branched-chain amino acids and immunity. J Nutr
136:288S–293S
Calders P, Pannier JL, Matthys DM, Lacroix EM (1997) Pre-exercise
branched-chain amino acid administration increases endurance
performance in rats. Med Sci Sports Exerc 29:1182–1186
Calders P, Matthys D, Derave W, Pannier JL (1999) Effect of
branched-chain amino acids (BCAA), glucose, and glucose plus
BCAA on endurance performance in rats. Med Sci Sports Exerc
31:583–587
Coombes JS, McNaughton LR (2000) Effects of branched-chain
amino acid supplementation on serum creatine kinase and lactate
dehydrogenase after prolonged exercise. J Sports Med Phys Fit
40:240–246
Crowe MJ, Weatherson JN, Bowden BF (2006) Effects of dietary leu-
cine supplementation on exercise performance. Eur J Appl Phys-
iol 97:664–672. doi:10.1007/s00421-005-0036-1
Davis JM, Bailey SP, Woods JA, Galiano FJ, Hamilton MT, Bartoli
WP (1992) Effects of carbohydrate feedings on plasma free
tryptophan and branched-chain amino acids during prolonged
cycling. Eur J Appl Physiol 65:513–519
Davis JM, Welsh RS, De Volve KL, Alderson NA (1999) Effects of
branched-chain amino acids and carbohydrate on fatigue during
intermittent, high-intensity running. Int J Sports Med 20:309–
314. doi:10.1055/s-2007-971136
Davis JM, Alderson NL, Welsh RS (2000) Serotonin and central nerv-
ous system fatigue: nutritional considerations. Am J Clin Nutr
72:573S–578S
De Lorenzo A, Petroni ML, Masala S, Melchiorri G, Pietrantuono
M, Perriello G, Andreoli A (2003) Effect of acute and chronic
branched-chain amino acids on energy metabolism and muscle
performance. Diabetes Nutr Metab 16:291–297
Gibala MJ (2007) Protein metabolism and endurance exercise. Sports
Med 37:337–340
Gleeson M (2005) Interrelationship between physical activity and
branched-chain amino acids. J Nutr 135:1591S–1595S
Gleeson M (2007) Immune function in sport and exercise. J Appl
Physiol 103:693–699. doi:10.1152/japplphysiol.00008.2007
Greer BK, Woodard JL, White JP, Arguello EM, Haymes EM (2007)
Branched-chain amino acid supplementation and indicators of
muscle damage after endurance exercise. Int J Sport Nutr Exerc
Metab 17:595–607
Howatson G, Hoad M, Goodall S, Tallent J, Bell PG, French DN
(2012) Exercise-induced muscle damage is reduced in resist-
ance-trained males by branched chain amino acids: a rand-
omized, double-blind, placebo controlled study. J Int Soc Sports
Nutr 9:20. doi:10.1186/1550-2783-9-20
Layman DK (2002) Role of leucine in protein metabolism during
exercise and recovery. Can J Appl Physiol Revue canadienne de
physiologie appliquee 27:646–663
MacLean DA, Graham TE, Saltin B (1994) Branched-chain amino
acids augment ammonia metabolism while attenuating protein
breakdown during exercise. Am J Physiol 267:E1010–E1022
Madsen K, MacLean DA, Kiens B, Christensen D (1996) Effects of
glucose, glucose plus branched-chain amino acids, or placebo on
bike performance over 100 km. J Appl Physiol 81:2644–2650
Nakamura I, Ochiai K, Imai Y, Moriyasu F, Imawari M (2007) Res-
toration of innate host defense responses by oral supplementa-
tion of branched-chain amino acids in decompensated cirrhotic
Ten weeks of branched-chain amino acid supplementation improves select performance and…
1 3
patients. Hepatol Res Off J Jpn Soc Hepatol 37:1062–1067.
doi:10.1111/j.1872-034X.2007.00166.x
Newsholme EA, Blomstrand E (2006) Branched-chain amino acids
and central fatigue. J Nutr 136:274S–276S
Newsholme EA, Blomstrand E, Hassmen P, Ekblom B (1991) Physi-
cal and mental fatigue: do changes in plasma amino acids play a
role? Biochem Soc Trans 19:358–362
Nieman DC (1997) Risk of upper respiratory tract infection in ath-
letes: an epidemiologic and immunologic perspective. J Athl
Train 32:344–349
Peake JM (2002) Exercise-induced alterations in neutrophil degranu-
lation and respiratory burst activity: possible mechanisms of
action. Exerc Immunol Rev 8:49–100
Pedersen BK et al (1997) Exercise-induced immunomodulation—
possible roles of neuroendocrine and metabolic factors Interna-
tional journal of sports medicine 18 Suppl 1:S2–7 doi:10.105
5/s-2007-972695
Rennie MJ, Tipton KD (2000) Protein and amino acid metabolism
during and after exercise and the effects of nutrition. Annu Rev
Nutr 20:457–483. doi:10.1146/annurev.nutr.20.1.457
Shimomura Y, Murakami T, Nakai N, Nagasaki M, Harris RA
(2004) Exercise promotes BCAA catabolism: effects of BCAA
supplementation on skeletal muscle during exercise. J Nutr
134:1583S–1587S
Suzuki K et al (1996) Capacity of circulating neutrophils to produce
reactive oxygen species after exhaustive exercise. J Appl Physiol
81:1213–1222
Suzuki K et al (1999) Endurance exercise causes interaction among
stress hormones, cytokines, neutrophil dynamics, and muscle
damage. J Appl Physiol 87:1360–1367
Tokish JM, Kocher MS, Hawkins RJ (2004) Ergogenic aids:
a review of basic science, performance, side effects,
and status in sports. Am J Sports Med 32:1543–1553.
doi:10.1177/0363546504268041
Toone RJ, Betts JA (2010) Isocaloric carbohydrate versus carbohy-
drate-protein ingestion and cycling time-trial performance. Int J
Sport Nutr Exerc Metab 20:34–43
van Hall G, MacLean DA, Saltin B, Wagenmakers AJ (1996) Mech-
anisms of activation of muscle branched-chain alpha-keto
acid dehydrogenase during exercise in man. J Physiol 494(Pt
3):899–905
Watson P, Shirreffs SM, Maughan RJ (2004) The effect of acute
branched-chain amino acid supplementation on prolonged
exercise capacity in a warm environment. Eur J Appl Physiol
93:306–314. doi:10.1007/s00421-004-1206-2
ResearchGate has not been able to resolve any citations for this publication.
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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.
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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.
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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. min-1.kg-1 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.
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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.
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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.