BCAAs are branched-chain amino acids, which are essential because the body cannot produce them. Leucine, a key component of BCAAs, is the most powerful amino acid in the entire aminogram. It enables optimal protein synthesis, which is essential for muscle building. It also accelerates muscle recovery after exercise and delays fatigue during exercise. BCAAs are by far the most important amino acids in supporting anabolism. No phase of muscle building or muscle definition can be optimal without BCAA intake. Isoleucine and valine work synergistically and, in addition to fighting muscle catabolism, help to better manage energy intake. During muscle mass gain or definition phases, a high protein intake is required to stimulate muscle growth. Proteins such as whey or isolate are the basis of supplementation because they have a very short assimilation time, which is essential for muscle recovery and to counteract catabolism. BCAAs come into play in their ability to increase muscle volume by accelerating and improving protein synthesis. Thus, it is often said that BCAAs are “protein fixers.”