Suplementação com aminoácidos de cadeia ramificada (AACR): efeitos sobre o desempenho físico no calor em humanos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

There are evidences that serotonin is linked to central fatigue processes and in hyperthermic stress its activity is enhanced. In order to diminish central serotonergic activation and improve performance, nutritional strategies with branched-chain amino acids (BCAA) has sought to prevent tryptophan influx to CNS, because these amino acids compete amongst themselves for the same transport system to the brain. The aim of this study was to assess the effect of environment [temperate (23°C and 60% rh) and hot (35°C and 60% rh)] and of AACR supplementation in hot environment in physical performance. 10 male volunteers participated in this study (age: 24,7±1 y; body mass: 79,4±2 kg; VO2max: 46±1 mL.kg-1.min-1). The volunteers cycled in a cycloergometer at 40% of Pmax (previously stablished) until fatigue in three experimental situations: 1) TEMP (temperate); 2) hot_PLA (placebo) and 3) hot_AACR. In these situations, they ingested 4.0 mL.kg-1bodyweight of a beverage [non-caloric artificial flavor juice with (hot_AACR) or without (hot_PLA and TEMP) AACR (0.03gAACR.kg-1bodyweight)] every one hour before the exercise (2 times), in the beginning and each 30 minutes during exercise. It was recorded the total time of exercise (TTE), sweat rate, oxygen consumption (VO2), core temperature (Tc), mean skin temperature (Tsk), body temperature (Tb), heart rate (HR), rate of perceived exertion (RPE) and thermal sensation. Glucose, lactate, free-fatty acids (FFA) were analyzed as well as prolactin (PRL) which was used as a peripheral marker of serotonergic activation. The experimental sessions were distributed randomly and each one was separeted by one week. The experimental design was doble-blind. For statistical analysis, the level of significance adopted was p=0.05 and the data are 15 expressed as means ± e.p.m. In hot environment, AACR supplementation does not improve physical performance. TTE was diminished in relation to temperate environment (p<0.001) [hot_AACR: 128.1±12,8 min.; hot_PLA: 126,3±9,9 min.; TEMP: 166±16,8 min]. In the heat, higher sweat rate, VO2, HR, Tb, Tsk, and thermal sensations were observed. RPE was higher after 60 minutes of exercise. At fatigue, Tc and plasma PRL levels were augmented in the heat, but AACR supplementation did not change the values of these parameters. There was no significant difference in thermoregulatory variables (sweat rate, Tc, Tsk and Tb) between hot_PLA and hot_AACR in any moment during exercise, but it was higher at the moment of fatigue, when compared to TEMP (p<0.001). There was a significant correlation between plasma PRL concentration and core temperature during hot_PLA and hot_AACR (p<0.05). The results of this study confirm that heat reduces performance (aprox. 30%), probably by the effects of higher corporal heat. AACR supplementation during prolonged physical exercise in a hot environment was not able to modify fatigue mechanisms induced by heat, possibly by ineffectiveness to change serotonergic activity.

ASSUNTO(S)

aminoácidos de cadeia ramificada decs temperatura corporal decs serotonina teses. educação física teses. exercícios físicos aspectos fisiológicos teses. fadiga aspectos fisiológicos teses.

ACESSO AO ARTIGO

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