These are the amino acids Leucine, Isoleucine and Valine which are oxidized by muscle to liberate energy. They are all Essential Amino Acids which means they must be provided in the diet. It has been suggested that supplementing them may improve performance by sparing the use of carbohydrate and glycogen as energy sources, thus reducing lactic acid generation and consequent fatigue. At very low exercise intensity BCAA supplements have been shown to lower blood lactate during and after exercise but at higher intensity no reduction in lactate or improvement in performance were seen.
Provision of supplemental BCAA’s may be of benefit by reducing the catabolism (breakdown) of muscle proteins to liberate them when they are in short supply following exercise. An alternative to BCAA supplements is provision of a group of the six amino acids lost in sweat which may prevent muscle protein breakdown and loss of BCAA’s happening in the first place. See Sweat & Amino Acids