BCAAs (Branched-Chain Amino Acids) are three: Leucine, Isoleucine and Valine. They are called branched due to their chemical structure similar to a branch. These three amino acids are part of the Essential Amino Acids; they cannot be produced by our body and they are necessary for its functioning, therefore we must ingest them through food or supplements.
BCAAs constitute the third part of the composition of the muscle and start the synthesis of protein, so they are essential for the maintenance and growth of muscles. In addition, they are part of other vital functions such as repairing tissues and forming cells.
During training, the body needs some nutrients to use as a source of energy. In strength or endurance exercises, muscles are under great tension. In order to respond adequately, the body uses carbohydrates and amino acids to produce energy. If the body is deprived of these energy sources, it will steal the amino acids present in the muscles to supply that demand, which will lead to the loss of muscle mass. For this reason, the body prefers to use BCAAs to transform them into energy. Consuming Branched-Chain Amino Acids during exercise prevents the body from losing muscle mass; in this way, muscles continue to synthesize proteins, and due to this process muscle mass is gained.