Unlike other essential amino acids, which are broken down in the liver, BCAAs are oxidized, or used for energy, primarily in the skeletal muscle.  BCAA oxidation in skeletal muscle increases 2-3 fold during exercise (Tarnopolsky, 2004; Shimomura et al., 2006).

In addition to being a source of fuel for working muscles, BCAAs are critical to muscle recovery and synthesis (reviewed in Shimomura et al., 2006; Blomstrand et al., 2006) and supplementation  with BCAAs has been shown to decrease delayed onset muscle soreness or DOMS (Greer et al., 2007; Shimomura et al., 2010).