Effect of BCAA supplementation on central fatigue, energy metabolism substrate and muscle damage to the exercise: a systematic review with meta-analysis

Background and aims: Current state of evidence recommends beneficial effects of branched chain amino acids (BCAAs) on exercise performance; however, randomized controlled trials (RCTs) of BCAA supplementation yield discordant results. The objective of this study was to clarify the effects of BCAA supplementation in exercise through meta-analysis of all relevant RCTs.Methods: A comprehensive search of PubMed, Embase, ISI web of science, and the Cochrane library has been conducted from inception to September 2016. This meta-analysis includes 31 primary trials of the effect of BCAA supplementation on central fatigue, fatigue substances (lactate and ammonia), energy metabolites (glucose and free fatty acids) and, muscle damage substances (LDH and CK). The estimates were either obtained from a fixed-effects model or a random-effects model. The studies' heterogeneity was calculated by Cochrane's test and I-2 index.Results: BCAA had no effect on central fatigue (SMD -0.31, 95% CI -0.72 to 0.09; p=0.1; heterogeneity I-2=0%, p=0.9). However, a significant reduction was detected in the lactate levels (WMD -0.16, 95% CI -0.26 to -0.53; p=0.003; heterogeneity I-2=47.9%, p=0.023). Moreover, BCAA supplementation had beneficial effects on ammonia, glucose, FFA, and CK, but had no effects on LDH.Conclusion: BCAA supplementation did not have any effect on the feeling of fatigue; however, it led to a favorable effect on fatigue substances, energy metabolites and muscle soreness substances. Therefore, it can be concluded that the ingestion of the BCAA can play a helpful role in the enhancement of the exercise performance.