They are the essential amino acids that our body cannot create on its own. They must be ingested through food or supplements. When we exercise, we tear muscle. It's a FACT that the human body depletes muscle at a faster rate than it repairs it. BCAAs trigger protein synthesis and inhibit the breakdown of muscle cells. The more BCAAs that are present in the muscles, the more they will be used for energy, slowing the breakdown of muscle cells and preventing muscle loss.