Leucine

This is one of the most important amino acids for hard training body builders. Leucine and the other branched chain amino acids (BCAAs), isoleucine, and valine, escape liver metabolism and can directly and significantly influence muscle-protein metabolism. Dietary leucine serves as a substrate for muscle metabolism during periods of cellular energy depletion, there by sparing critical contractile and enzyme muscle protein from degradation to supply leucine requirements.

Because leucine contributes to gluterine synthesis, taking supplemental leucine before and after intense training and between meals can help normalize glutimine levels in both the serum and muscle, thereby promoting anticatabolic muscle metabolism as well as supporting immune function.