Post exercise muscle soreness is caused by muscle fiber damage and inflammation developed during tissue repair.  Muscle cells use amino acids as building blocks to repair tissue and make new contractile proteins.  Amino acid supplements might prevent soreness and promote post training gains in muscle mass and strength.  Leucine, a branched chain amino acid, activates biochemical pathways in muscles that stimulate protein synthesis.  British researchers found that supplementing branched chain amino acids before and after intense training reduced soreness and biochemical markers of muscle damage.  Branched chain amino acid supplements may help bodybuilders and weightlifters accommodate to intense weight training programs.  (Journal International Society of Sports Nutrition, 9:  20, 2012)