BCAAs (branched-chain amino acids) are three essential amino acids — leucine, isoleucine, and valine — that your body can't produce on its own. They play a direct role in muscle protein synthesis, reducing muscle breakdown during exercise, and delaying central fatigue. Leucine is the standout, acting as the primary trigger for muscle building through the mTOR pathway. The honest truth? If you eat adequate protein, you're likely getting enough BCAAs from food. But as part of a pre workout formula, they provide targeted muscle-protective support during training when it matters most.