The best athletes can train hard, recover quickly, and train hard again.  David Pearson from Ball State University and Carwyn Sharp found amino acid supplements taken for four weeks promoted recovery from an intense workout.  During recovery following amino acid supplementations, athletes showed higher levels of testosterone and lower levels of cortisol (breaks down tissue) and creatine kinase (marker of muscle damage).  Dialy amino acid intake from the supplement included 2,000 micrograms of L-glutamine, 1,800 micrograms of L-leucine, 700 micrograms of L-isoleucine, and 750 micrograms of L-valine.  Amino acids are the building blocks of proteins but some act as signaling chemicals for important metabolic pathways that synthesize proteins and promote tissue repair.  Intense training is the key to building strength, power, and muscle mass.  Amino acid supplements might help you train hard, recover, and then train hard again.  (Journal Strength Conditioning Research, 24:  1125-1130, 2010)