L-Leucine, L-Isoleucine, and L-Valine are commonly grouped together and referred to as Branched Chain Amino Acids, or BCAAs, because of their unique branched chemical structure. BCAAs are essential, meaning that they must be consumed through the diet, since the human body can not make them from other compounds. BCAAs have long been used by strength-training and endurance athletes alike to activate muscle synthesis and reduce muscle breakdown caused by intense training.