Usn nutrition bcaa syntho stack is a complete amino acid stack supplement it delivers key bcaarsquos branched chain amino acids to our muscles which help prevent catabolismr bcaas are vital for any athlete and from the building blocks of protein a necessity for muscle recovery due to protein synthesisr usn nutrition bcaa syntho stack is an effective bcaa branched chain amino acid supplement it also provides you with alpha lipoic acid alongside the 3 essential amino acids leucine is