BCAAs are a group of essential amino acids that play a key role in protein synthesis (a.k.a. muscle growth) and energy production. BCAAs include L-leucine, L-Valine and L-Isoleucine. BCAAs make up 35 to 40% of essential amino acids in total body protein.
BCAAs are essential amino acids and cannot be made by the body. They must be ingested through food or supplementation. During exercise, BCAA metabolism in muscle tissue is increased. Therefore, after aerobic exercise (i.e., cardio) and anaerobic exercise (i.e., weight training) there is a significant decrease in plasma BCAA levels in muscle tissue.