When working out, the important thing is to promote muscle maintenance and its growth. The protein is composed of amino acids and BCAAs refer to three of the 20 amino acids – leucine, isoleucine and valine, and these cannot be synthesised by the body and must therefore be provided in the diet. BCAAs constitute approximately 1/3 of skeletal muscle protein. BCAAs are the building blocks of protein. They are a rapid supplement which are metabolised primarily in skeletal muscle, they directly enter our bloodstream to provide the body with essential amino acids.