The amino acids arginine and ornithine have been shown to support healthy growth hormone production. Growth hormone is naturally released by the pituitary gland in response to sleep and exercise in order to help replenish tissues. It supports muscle protein synthesis, moderates the breakdown of muscle tissue and promotes fat utilization for energy. Arginine supports healthy growth hormone synthesis and is also a precursor for protein synthesis. Ornithine alpha-ketoglutarate (OKG) has indicated the ability to support healthy nitrogen balance, important for healthy muscle function. OKG also promotes healthy polyamine, arginine and glutamine levels, important metabolites for muscle protein support. One study suggested the potential for arginine and ornithine in combination to support lean muscle mass when combined with physical training. A second study also suggests a possible role of arginine and ornithine in supporting lean muscle mass and strength training when combined with a high intensity exercise program. Taken one hour before physical activity or bedtime, arginine and OKG may support healthy growth hormone production and may also promote healthy muscle protein synthesis, muscle recovery, and lean muscle mass when combined with physical training.