SUPLENTAÇÃO COM GLUTAMINA PEPTÍDEO PARA ATLETA DE FUTEBOL

27
CLINICS 2008;63(1):27-32
CLINICAL SCIENCE
a Institute of Orthopedics and Traumatology, Hospital das Clínicas, Faculdade
de Medicina da Universidade de São Paulo - São Paulo/SP, Brazil.
b Statistics Department, Universidade de Brasília - Brasília/DF, Brazil.
alefavano@uol.com.br
Received for publication on September 17, 2007.
Accepted for publication on October 04, 2007.
PEPTIDE GLUTAMINE SUPPLEMENTATION FOR
TOLERANCE OF INTERMITTENT EXERCISE IN
SOCCER PLAYERS
Alessandra Favanoa, Paulo Roberto Santos-Silvaa, Eduardo Yoshio Nakanob,
André Pedrinellia, Arnaldo José Hernandeza, Julia Maria D´Andrea Grevea
Favano A, Santos-Silva PR, Nakano EY, Pedrinelli A, Hernandez AJ, Greve JMD. Peptide glutamine supplementation for
tolerance of intermittent exercise in soccer players. Clinics. 2008;63(1);27-32.
OBJECTIVE: To investigate whether supplementation of carbohydrate together with peptide glutamine would increase exercise
tolerance in soccer players.
METHODS: Nine male soccer players (mean age: 18.4 ± 1.1 years; body mass: 69.2 ± 4.6 kg; height: 175.5 ± 7.3 cm; and
maximum oxygen consumption of 57.7 ± 4.8 ml.kg-1.min-1) were evaluated. All of them underwent a cardiopulmonary exercise
test and followed a protocol that simulated the movements of a soccer game in order to evaluate their tolerance to intermittent
exercise. By means of a draw, either carbohydrate with peptide glutamine (CARBOGLUT: 50g of maltodextrin + 3.5g of peptide
glutamine in 250 ml of water) or carbohydrate alone (CARBO: 50g of maltodextrin in 250 ml of water) was administered in order
to investigate the enhancement of the soccer players’ performances. The solution was given thirty minutes before beginning the
test, which was performed twice with a one-week interval between tests.
RESULTS: A great improvement in the time and distance covered was observed when the athletes consumed the CARBOGLUT
mixture. Total distance covered was 12750 ± 4037m when using CARBO, and 15571 ± 4184m when using CARBOGLUT
(p<0.01); total duration of tolerance was 73 ± 23 min when using CARBO and 88 ± 24 min when using CARBOGLUT (p<0.01).
CONCLUSION: The CARBOGLUT mixture was more efficient in increasing the distance covered and the length of time for
which intermittent exercise was tolerated. CARBOGLUT also reduced feelings of fatigue in the players compared with the use of
the CARBO mixture alone.
KEYWORDS: Fatigue. Tolerance. Glutamine Supplementation. Carbohydrate Supplementation. Soccer players.
INTRODUCTION
Soccer is the most popular sport in Brazil. The International
Federation of Football Association (FIFA) considers
it to be the game that is most widely played worldwide
by individuals with the widest diversity of socioeconomic
status. According to data from the Brazilian Football Confederation
(CBF), there are around 30 million soccer players
in Brazil. Out of this total, 11,000 are registered players.
1
Soccer is a competitive acyclic activity of long duration
practiced through intermittent movements with varying
degrees of intensity that require participation by three
energy-providing systems.2 Today’s players move at high
speed and can cover an average distance of 10 to 14 km
by the end of a game, mostly depending upon the player’s
position and the importance of the match, though the relative
distribution of distance by speed has remained somewhat
constant .3-4
This new profile presented by soccer demands the use
of new strategies. One of these is a nutritional strategy that
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Peptide glutamine supplementation for tolerance of intermittent exercise in soccer players CLINICS 2008;63(1):27-32
Favano A et al.
aims to compensate for the higher metabolic rates during
training and the game itself. Currently, ergogenic nutritional
supplements are used to increase energy production and,
consequently, to compensate for the metabolic needs of athletes
in different sports.5-8
Athletes in long-duration types of sports (e.g., runners,
triathletes and cyclists) have been benefiting from the use
of carbohydrate and glutamine together. Glutamine is an
intermediate metabolite in the Krebs cycle and thus acts
in gluconeogenesis by saving phosphocreatine (CP) deposits
and glycogen in muscle fibers, particularly type I (aerobic)
fibers, thereby increasing the tolerance to exercise.9-11
This is the most likely hypothesis for its influence on performance.
Moreover, peptide glutamine is scientifically considered
to be an essential nutrient for conditioning, and in sports
nutrition, it plays an important role in preventing athlete
fatigue and overtraining syndrome. The benefits of its use,
in terms of the immune response to athlete nutrition and
nitrogen balance, are well established.12 For example, athletes
consuming beverages containing glutamine following
rowing competitions and marathons (5g glutamine after the
activity and two hours later) experienced fewer upper respiratory
tract infections (URTI).13-15
However, in contrast to other types of sports, there is a
lack of research on the use of glutamine in relation to soccer
performance. Therefore, the aim of the present study
was to investigate whether supplementation of carbohydrate
together with peptide glutamine would increase exercise
tolerance in soccer players.
MATERIALS AND METHODS
Nine top-level male soccer players from professional
soccer teams in the state of São Paulo (age: 18.4 ± 1.1
years; body mass: 69.2 ± 4.6 kg; height: 175.5 ± 7.3 cm;
and maximum oxygen consumption 57.7 ± 4.8 ml.kg-1.min-
1) participated in the study. All of these athletes were training
for approximately 10 hours per week and were taking
part in official competitions in Brazil.
Before undergoing the tests, the players were given explanations
about the assessment procedures, the study objectives,
and the possible benefits and risks. They all signed
a statement of consent in accordance with the requirements
of the Institution’s Ethics Committee (National Health
Board Resolution No. 196/96), under CAPPESQ protocol
No. 938/05. The subjects were permitted to withdraw at any
time for any reason. The following inclusion criteria were
used: 1) age between 17 and 20 years; 2) officially registered
soccer players; and 3) laboratory test results
(hemogram, cholesterol and fractions, triglycerides, total
protein and fractions, urea, creatinine, uric acid and minerals)
within the normal standard ranges.
Exercise capacity was tested on a motorized treadmill
(ATL – 10.200, Inbramed Instruments, Porto Alegre, Brazil)
using an incremental protocol and a fixed inclination
of 3%. Under this protocol, the players remained at rest
for two minutes, and then warmed up for three minutes at
speeds of 4.8, 6.0 and 7.2 km.h-1 per minute. The test began
at 8.4 km.h-1 with increments of 1.2 km.h-1 every two
minutes until the subjects reached volitional fatigue.16 Their
subjective perception of their own effort was determined
for each test period using Borg’s 15-point linear scale for
rating perceived exertion.17 Moreover, verbal encouragement
was used during the tests.18
Pulmonary ventilation (VE), oxygen consumption (VO2),
carbon dioxide production (VCO2) and respiratory exchange
ratio (RER) were continuously monitored by means
of a breath-by-breath system (MedGraphics CPX/D, St.
Paul, MN, USA). This metabolic device measures expired
airflow by means of a pneumotach connected to the mouthpiece.
A sample line was connected to the pneumotach,
from which air was continuously pumped to O2 and CO2
gas analyzers. Prior to testing, the pneumotach was calibrated
with ten samples from a 3-L calibration syringe
(5530, Hans Rudolph, USA). The gas analyzers were also
calibrated before and after each test in relation to room air
and medically certified calibration gases (11.9% and 20.9%
O2 and 5.12% CO2, respectively), balanced with nitrogen
(N2)19-20. Heart rate (HR) was continuously recorded during
exercise by means of electrocardiography (6.4,
HeartWare Instruments, Belo Horizonte, Brazil). Maximal
oxygen uptake was assessed when the following criteria
were satisfied: a) no increase in VO2max greater than 2.0
ml.kg-1.min-1 at maximum effort; b) maximal respiratory
exchange ratio (RER) ≥1.10; c) maximal HR within 10
beats/min of the age-predicted maximum (208 – [age x
0.7]); and d) more than 18 on Borg’s scale.21-25 All the subjects
evaluated satisfied at least two criteria.
To test the level of tolerance to intermittent exercise,
the soccer players followed a specific protocol on the motorized
treadmill (Table 1) that simulated movements during
a game (walking, running, jogging and sprinting) on
the field. Each five-phase battery of tests lasted 25 minutes.
To verify the players’ feelings of fatigue and their volitional
exhaustion, Borg’s scale was used.13 The athletes
served as their own controls, taking the test twice with an
interval of one week between the tests.
The athletes took either carbohydrate with glutamine
peptide (named CARBOGLUT) at a concentration of 50g
of maltodextrin + 3.5g of glutamine peptide in 250 ml of
water, or a single carbohydrate (named CARBO) at a con29
CLINICS 2008;63(1):27-32 Peptide glutamine supplementation for tolerance of intermittent exercise in soccer players
Favano A et al.
centration of 50g of maltodextrin in 250 ml of water. These
supplements were administered thirty minutes before beginning
the test. Carbohydrate was used as the control because
it is a commonly used supplement in soccer and its
effect on athletes’ performance is well known. Thus, the
aim was to investigate whether the addition of glutamine
to a carbohydrate beverage could enhance the performance
even further. The soccer players were randomized in a double-
blind manner, i.e., none of the staff responsible for or
involved in the experiment or the evaluation of the procedures,
or the athletes themselves, had any knowledge of
which solution had been consumed. These solutions were
prepared by an independent evaluator and all had the same
taste (grape).
Statistical Analysis
The data analysis was performed using SPSS software
(Statistical Package for the Social Sciences) for Windows,
version 11.5. The means on Borg’s scale for the
CARBOGLUT and CARBO groups were compared. These
means were then subjected to Wilcoxon’s test26 to determine
their statistical significance. To investigate the effect of the
supplementation on both the distance covered and the duration
of tolerance, the means for the players in the
CARBOGLUT and CARBO groups were compared. Statistical
significance was determined using the paired Student’s
t test and the data are presented as means ± standard
deviation (SD). For both tests, a significance level of
5% was set.
RESULTS
The means on Borg’s scale for the CARBOGLUT and
CARBO groups were different. The CARBOGLUT group
experienced less fatigue. This fatigue was significantly less
when both the first and the second batteries were analyzed
(p=0.047 and p=0.008, respectively), but the difference was
not significant at the significance level of 0.05 when the
third battery was considered (p=0.125) (Table 2). It should
be noted that this low tendency towards feelings of fatigue
in the CARBOGLUT group was observed during the entire
test. Over the course of the test, the subjective perception
of fatigue was measured at the end of each stage (after
5 minutes). Figures 1.A and 1.B present the distribution
on Borg’s scale for the CARBOGLUT and CARBO
groups at the end of each stage, and show a low tendency
towards fatigue in the CARBOGLUT group. Figures 1.A
and 1.B show that 65% of the athletes in the CARBOGLUT
group had still not achieved a score of 15 on the Borg scale
30 minutes after the test (the mean time for the
CARBOGLUT athletes to achieve a score of 15 on Borg’s
scale - see Table 4); 55 minutes after the test (the mean
time for the CARBO athletes to achieve a score of 20 on
Borg’s scale – see Table 4), only 33% of the athletes in
the CARBOGLUT group achieved a score of 20 on Borg’s
scale, and 11% of them still presented a score on Borg’s
scale that was lower than 10.
The mean distances covered by the CARBOGLUT and
CARBO groups were different (Table 3). It should be noted
that when the mean distances covered (maximum distance)
Table 1 – Design of the intermittent tolerance exercise protocol used by the soccer players.
ACTIVITY Phase 1 (km.h-1) Phase 2 (km.h-1) Phase 3 (km.h-1) Phase 4 (km.h-1) Phase 5 (km.h-1)
Walking 3.0 – 1’ 4.0 – 1’ 3.0 – 1’ 4.0 – 1’ 5.0 – 1’
Running 12.0 –1’ 13.0 –1’ 12.0 –1’ 13.0 –1’ 15.0 –1’
Jogging 8.0 – 2’ 9.0 – 2’ 8.0 – 2’ 9.0 – 2’ 10.0 – 2’
Sprinting 18.0 – 1’ 19.0 – 1’ 18.0 – 1’ 19.0 – 1’ 19.0 – 1’
Note: A complete battery is composed of five phases with a covered distance equivalent to 4418 m.
Table 2 – Perception of fatigue verified by the subjective Borg scale in three batteries of exercise in soccer players using
carbohydrate (CARBO) and the mixture carbohydrate and peptide glutamine (CARBOGLUT).
1st Battery 2nd Battery 3rd Battery
CARBO CARBOGLUT CARBO CARBOGLUT CARBO CARBOGLUT
N 9 9 9 9 7** 9
Minimum 10 9 14 13 20 16
Maximum 18 15 20 20 20 20
Mean 14.00 12.33 18.67 16.56 20.00 19.11
*P (difference) 0.047 0.008 0.125
* Wilcoxon’s test; ** Two GRII athletes did not tolerate up to third battery.
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Peptide glutamine supplementation for tolerance of intermittent exercise in soccer players CLINICS 2008;63(1):27-32
Favano A et al.
in the tolerance test performed by athletes supplemented
with CARBO (12750 ± 4037m) were compared with the
same athletes supplemented with CARBOGLUT (15571 ±
4187m), the CARBOGLUT group covered a significantly
greater distance (2822 ± 2771m; p=0.016). This was also
noticeable when the distances covered up to a rating of 15
on Borg’s scale, in which the distance covered by the
CARBOGLUT group increased by 1973 ± 1471m
(p=0.004). In addition, when the mean distances covered
up to 20 on Borg’s scale were measured, the CARBOGLUT
group covered 3155 ± 1607m (p<0.001) more than the
CARBO group did.
Table 4 presents a comparison between the results from
the mean time elapsed for the players in the CARBOGLUT
and CARBO groups. This shows that, on average, the players
in the CARBOGLUT group persisted for significantly
longer (15.6 ± 15.6 min; p=0.017) than the CARBO group
players did. This also occurred when times to scores of 15
and 20 on Borg’s scale were compared, in which the players
in the CARBOGLUT group presented increases of 11.1
± 8.2 min (p=0.004) and 17.2 ± 10.0 min (p=0.001), respectively.
Figures 1A and 1B - Percentage of perceived effort distributions on the
Borg scale during test utilizing supplementation with CARBO and
CARBOGLUT.
Table 3 – Comparison of the distance covered in relation to the perception of fatigue verified by the subjective Borg scale
at three moments of exercise in soccer players supplemented with carbohydrate alone (CARBO) and the mixture of
carbohydrate and peptide glutamine (CARBOGLUT).
Borg = 15 Borg = 20 End of the test
(tired) (maximum effort) (maximum tolerance)
CARBO CARBOGLUT CARBO CARBOGLUT CARBO CARBOGLUT
N 9 9 9 9 9 9
Mean 5516 7489 9261 12416 12750 15571
SD 2341 2197 2862 3663 4037 4187
IC 95% (3716; 7316) (5800; 9177) (7061;11462) (9601;15232) (9647;15852) (12353;18790)
Difference N 9 9 9
Mean 1973 3155 2822
SD 1471 1607 2771
IC 95% (842 ; 3104) (1920 ; 4390) (692 ; 4952)
P 0.004 < 0.001 0.016
Table 4 – Comparison of the lapse of time to the perception of fatigue verified by the subjective Borg scale at three
moments of exercise in relation to the soccer players with supplementation of carbohydrate (CARBO) and the mixture of
carbohydrate and peptide glutamine (CARBOGLUT).
Borg = 15 Borg = 20 End of the test
(tired) (maximum effort) (maximum tolerance)
CARBO CARBOGLUT CARBO CARBOGLUT CARBO CARBOGLUT
N 9 9 9 9 9 9
Mean 31.7 42.8 52.8 70.0 72.8 88.3
SD 13.2 12.5 16.0 21.1 22.9 23.7
CI 95% (21.5; 41.8) (33.2; 52.4) (40.5; 65.1) (53.8; 86.2) (55.2; 90.4) (70.1; 106.6)
Difference N 9 9 9
Mean 11.1 17.2 15.6
SD 8.2 10.0 15.6
CI 95% (4.8 ; 17.4) (9.5 ; 24.9) (3.6 ; 27.6)
P 0.004 0.001 0.017
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Favano A et al.
DISCUSSION
This study shows for the first time the effect of combined
supplementation of carbohydrate and glutamine on
soccer players’ performances with regard to intermittent
physical activity. As such, feelings of fatigue were measured
using an intermittent effort protocol that simulated
soccer players’ activities. The measurements obtained were
compared between the CARBOGLUT and CARBO groups
using Borg’s scale. The results obtained showed the substantial
effect of the CARBOGLUT mixture on the soccer
players’ physical performance when compared with the use
of CARBO alone.
The results presented in Table 2 show that the
CARBOGLUT group presented a low tendency towards feelings
of fatigue. This fatigue was significantly lower when
both the first and second batteries were analyzed, but it was
not significant at the level of 0.05 when the third battery was
considered. However, the test on the third battery was probably
compromised because of the small size of the sample,
considering that not all of the players in the CARBO group
were able to participate. Thus, a more conclusive test should
be conducted with a larger number of athletes.
When the mean distances in the soccer players’ tolerance
tests were compared, the CARBOGLUT group covered
a significantly greater distance than the CARBO group
did. The players with CARBOGLUT supplementation covered,
on average, 3155m more than did those who received
CARBO alone. Recently, in a study of soccer players at a
high competitive level in Europe, Di Salvo et al.4 found
that they covered a mean distance of 11 km by the end of
a game. In the present study, the athletes receiving CARBO
alone covered a mean distance of around 12.7 km, while
those who received the CARBOGLUT mixture covered
15.5 km. This is 41% more than the distance covered in
high-level matches that was determined by Di Salvo et al.4
The same was also observed in relation to the duration of
exercise tolerance following the ingestion of
CARBOGLUT. Table 4 presents the results from comparing
the mean distances covered by the players in the
CARBOGLUT and CARBO groups, showing that, on average,
the players in the CARBOGLUT group could endure
significantly longer periods of exercise. On average,
the maximum tolerance of the players in the CARBOGLUT
group was 21% higher than the tolerance of players in the
CARBO group.
There are few studies that associate the effect of
glutamine with the performance of athletes because the
mechanisms involved are still unclear. However, one interesting
study27 carried out among triathletes found that
glutamine supplementation was efficiently absorbed and
was not used for enterocyte proliferation, thus making it
easier for the athletes receiving the supplementation to
maintain their glycemic levels and ensuring greater exercise
tolerance in these athletes. Additionally, in these athletes,
a tendency towards a lower subjective perception of
submaximal effort was observed among those who received
glutamine and maltodextrin supplementation in comparison
with those who received maltodextrin supplementation
alone. Another remarkable finding was that there was
higher maximum oxygen consumption (VO2max) at the second
ventilatory threshold (VT2) (maximal respiratory compensation
point) among the athletes who received supplementation.
This indicated greater efficiency in this parameter
for extracting O2 for equal maximal aerobic power. It
can therefore be said that the athletes who received
glutamine and maltodextrin supplementation presented a
higher aerobic capacity for submaximal effort.
Studies developed among cyclists and runners have also
found greater tolerance to effort when these athletes were
supplemented with peptide glutamine and carbohydrate.
This is because glutamine is an intermediate metabolite of
the Krebs cycle, and is thus thought to act in gluconeogenesis,
thereby increasing the efficiency of this metabolic
process.9-10 Hence, a higher efficiency of gluconeogenesis
for energy production by muscle glycogen is of fundamental
importance for higher performance in sports.
A study in which muscle biopsies were taken to investigate
the effects of CARBO ingestion with regard to phosphocreatine
(PC) degradation in muscle fiber types I (aerobic)
and II (anaerobic) during submaximal effort found that
ingestion of CARBO significantly (p<0.05) accentuated the
decline of PC concentration by 46% and 36% in type I and
type II fibers, respectively.11 These authors also observed
a 56% reduction in the use of muscle glycogen in type I
fibers, but not in type II fibers. They concluded that
CARBO supplementation during exhaustive sprints accentuated
the decline of ATP oxidative resynthesis of type I
fibers, as indicated by the greater PC and muscle glycogen
storage. In contrast, this response was not observed in
muscle glycogen in relation to type I fibers, which may reflect
different forms of recruitment.28
This response has important metabolic significance because
in our study the combined supplementation of
CARBOGLUT probably boosted the capability of the soccer
players’ muscles to use muscle glycogen more slowly.
Through this effect, glycogen content would be saved for
the more intense times of demand seen in soccer matches.
Tsintzas et al.11 showed that there was a slower CP reduction
in type I muscle fibers (resistant to fatigue) and type
II (nonresistant to fatigue), and also a slower reduction in
glycogen in type I muscle fibers.
32
Peptide glutamine supplementation for tolerance of intermittent exercise in soccer players CLINICS 2008;63(1):27-32
Favano A et al.
Soccer is a long-duration sport practiced with a variety
of intensities of aerobic and anaerobic stimuli throughout
the match, using both types of muscle fibers. For this reason,
greater muscle glycogen storage would surely bring
benefits in terms of better performance. The results from
this study offer exciting prospects in the field of peptide
glutamine utilization as an ergogenic aid for improving the
performance of athletes who take part in continuous and
intermittent activities of long duration.
In conclusion, the CARBOGLUT mixture was more efficient
in increasing athletes’ distance and duration of tolerance
to intermittent exercise, and in lowering feelings of
fatigue among the players when compared with the use of
CARBO alone. Thus, supplementation with both carbohydrate
and peptide glutamine improved the physical performance
of these soccer players.
It is important to critically evaluate the results and the
whole study. The present study has certain limitations that
need to be taken into account when considering the study
itself and its contributions to the field. Peptide glutamine
has often been used for immunological support for
immunosuppressed patients. Few scientific studies have
used peptide glutamine as an ergogenic aid for improving
athletic performance. In our study, we used this supplement
in an acute manner with excellent results, but in a small
sample. However, we do not know whether chronic use of
this supplement would lead to the same results in our study
population. Thus, we suggest that more research with other
study designs should be carried out in order to compare
whether other models of peptide glutamine use might be
more efficient in increasing the levels of tolerance among
soccer players. This field of research remains open, and
some of the limitations of this current study may be seen
as fruitful avenues for future research on this topic.
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