We are constantly reminded that amino acids
are the "building blocks" of muscle, but now science tells us that they also regulate anabolic and
catabolic hormone levels after strenuous weight training. In a recent study published in the Journal of Strength and Conditioning Research, scientists from the College of Charleston and Ball State University illustrated that an amino acid supplementation (total daily dose = L-leucine: 1800 mg, L-isoleucine: 750 mg, L-valine: 750 mg, L-glutamine: 2000 mg) increased serum testosterone concentration by almost 50% above baseline after intense resistance training; whereas, subjects who took a placebo saw a more than 30% decrease in serum testosterone concentration. As well, post-workout serum cortisol (a catabolic hormone) went down by over 1000% with amino acid supplementation, in contrast to a 1000% increase in cortisol in subjects who received the placebo.
With amino acid supplementation, the blood anabolic profile, as calculated by the ration of testosterone:cortisol, showed that there was a 1600% increase from baseline (compared to -300% change in the placebo group). The strong net anabolic response, in those who took amino acids, related to reduced exercise-induced muscle damage, as the authors also showed a 30% reduction in creatine kinase levels after heavy resistance exercise.
Sharp CP, Pearson DR. Amino Acid Supplements and Recovery from High-Intensity Resistance Training. J Strength Cond Res. 2010 Apr;24(4):1125-30.