Failure of acute BCAA supplementation to delay fatigue during exercise in a hot environment

Abstract

Serotonin is linked to central fatigue during exercise and its activity is enhanced in the heat. Branched‐chain amino acids (BCAA) have sought to diminish serotonergic activity and improve performance. We studied the effects of acute BCAA supplementation on physical performance and fatigue mechanisms in a hot environment (35°C and 60% rh). Ten young male participated in this study. They cycled at 40% of maximal power output (Pmax ) until fatigue in two experimental situations: PLA (placebo) and BCAA. In a double‐blind manner they ingested 4.0 mL.kg−1 b.w. of a non‐caloric artificial flavor juice, with (BCAA) or without (PLA) BCAA (0.03g BCAA.kg−1 body weight) before (twice), at the beginning and every 30 minutes during exercise. Total time of exercise (TTE), sweat rate, VO2, core temperature (Tc), mean skin temperature (Tsk), mean body temperature (Tb), heart rate (HR) and RPE were recorded. Plasma glucose, lactate and free‐fatty acids (FFA) as well as prolactin (PRL), a peripheral marker of serotonergic activity, were analyzed. Data are expressed as means ± e.p.m. BCAA didn't improve performance. At fatigue, Tc and plasma PRL augmented similarly in both conditions. There was no difference on sweat rate, Tc, Tsk and Tb between PLA and BCAA. Acute BCAA supplementation during exercise in a hot environment failed to modify fatigue induced by heat, possibly by its ineffectiveness to alter central serotonergic activity.