Of the eight essential amino acids that cannot be produced by the body, the three branched-chain aminos Leucine, Isoleucine and Valine are of key importance. Based on their unique structure, activity, storage and metabolism, BCAA's have become a staple in the lives of many athletes and physically active individuals. They account for nearly 1/3 of the amino acids in muscle protein, and play a number of key roles in the repair and growth of muscle tissues.