Branched-chain Amino Acids Ingestion Does Not Affect Endurance Performance

Branched-chain amino acids (BCAA) supplementation is one of the most popular dietary manipulations used by endurance athletes. However, the ergogenic role of these amino acids in endurance exercise is not well established yet. Therefore, the aim of this study was to evaluate the effect of BCAA supplementation upon endurance exercise performed until exhaustion. In order to induce glycogen supply reduction, and thus maximize BCAA utilization, the subjects (n=17) were submitted to a prior exercise trial (one bout of running at 75% of VO2max for 40 min followed by two bouts at 90% of VO2max for 10 min each). Subsequently, the participants performed an endurance test (running at 90% of the anaerobic threshold) until exhaustion after the ingestion of 77 mg.kg(-1) of BCAA or placebo, in a double blind crossover design. Both trials, BCAA and placebo, were a week apart. No differences were observed between placebo and BCAA experimental conditions regarding time to exhaustion (50.1 +/- 8.9 vs 52.4 +/- 4.5 min, respectively) and total distance performed (8.8 +/- 1.3 vs 9.1 +/- 0.6 km, respectively) in endurance capacity test. Furthermore, no difference was observed in glucose, lactate or ammonia plasma concentration between both experimental conditions. In conclusion, BCAA supplementation did not affect endurance exercise performance.