Cheuvront, S. N., Carter III, R., Kolka, M. A., Cadarette, B. S., & Sawka, M. N. (2004). Branched chain amino acids do not alter exercise performance in the heat. Medicine and Science in Sports and Exercise, 36(5), Supplement abstract 1981.

"Research examining the impact of branched chain amino acid (BC) supplementation on exercise performance is equivocal. However, one study demonstrated a benefit of BC when administered during exercise in the heat" (p. S283). This study investigated whether the administration of glucose plus branched chain amino acid would enhance performance in the heat (40°C, 20%rh) when compared to glucose only following a short period of exhaustive exercise and diet manipulation. On Day 1, heat-acclimated men (N = 5) performed exhaustive exercise and ate a controlled diet (3,262 kcal, 20% carbohydrate, 63% fat, 17% protein), the combination of which was designed to produce physiological perturbations consistent with the onset of central fatigue. On Day 2, Ss were randomly assigned ) to consume 1.2 L of isocaloric treatment (T = 10g/L BC: 55% valine, 30% leucine, 15% isoleucine and 60g/L glucose) or placebo drink (P = 10g/L maltodextrin and 60g/L glucose) during 60-minute of cycling in the heat at 50%VO2peak followed immediately by a cycling time trial. Performance was assessed as the mean power output achieved over 30 minutes.

No differences were observed between trials for measurements of heart rate, rectal temperature, rating of perceived exertion, thermal comfort, or level of dehydration incurred during exercise. Performance differences were nonsignificant. It is possible that some individuals react positively to branched chain amino acid while others do not. This would account for the nonsignificant results.

Implication. The combination of branched chain amino acid with carbohydrate provides no physiological or exercise performance advantage in the heat when compared to an isocaloric carbohydrate drink alone.

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