L-arginine is considered a semi-essential amino acid and is thought of as one of the bodybuilding amino acids because the body uses it to release growth hormone. Human growth hormone is used by the body to build muscle strength and tone and to enhance the burning of fats. L-arginine is important in the urea cycle for the metabolism of ammonia produced in the breakdown of protein. L-arginine also stimulates the production of nitric oxide which supports vasodilation. Free form amino acid, high purity, well tolerated.