Branched-chainamino acids (BCAAs) are Leucine, Valine and Isoleucine. They make up a third of the proteins used to build muscle. However, they are not manufactured by the body, but are found in our diet. BCAAs are used extensively during physical effort, as they also supply the body with energy. They therefore have two of the most important functions in a muscle-building program, but they are in very short supply. That's why taking BCAA supplements is essential for any athlete who wants to achieve consistent results!