Branched-chain amino acids (BCAAs) include leucine, isoleucine and valine. BCAAs are needed for the maintenance of muscle tissue; they are also needed during times of physical stress and intense exercise.
Periods of physical stress, such as intense weight lifting and long distance running can create a catabolic state in which muscle tissue is broken down. In these situations, supplemental BCAAs—particularly leucine and its derivatives ketoisocaproate (KIC) and hydroxymethylbutyrate (HMB)—can be beneficial in reducing protein breakdown. Nonetheless, BCAA supplements may reduce muscle loss and speed muscle gain. BCAAs may also be useful to anyone wanting to prevent muscle breakdown.