Arginine promotes increased nitric oxide (NO) production for enhanced blood flow and better delivery of oxygen and nutrients to working muscle.

Arginine (or L-arginine) is a crystalline free-form amino acid involved in numerous areas of human biochemistry, including muscle metabolism, ammonia detoxification, hormone secretion and the immune system. L-arginine is considered a semi-essential amino acid, because although it is normally synthesized in sufficient amounts by the body, supplementation is sometimes required. Arginine supports protein synthesis as it is involved in the transport and storage of nitrogen and is important for proper physical performance because it is used by the body to produce creatine.

L-arginine is required for the synthesis of nitric oxide, a secondary messenger involved in blood flow. Nitric oxide is a compound that helps keep blood vessels dilated to promote healthy blood flow. Preliminary evidence suggests that arginine may be useful in the treatment of medical conditions that are improved by vasodilation, such as angina, atherosclerosis, coronary artery disease, erectile dysfunction, heart failure, intermittent claudication/peripheral vascular disease, and vascular headache. Arginine also stimulates protein synthesis and has been studied for wound healing, bodybuilding, enhancement of sperm production (spermatogenesis), and prevention of wasting in people with critical illness. L-Arginine is beneficial for overall cardiovascular maintenance and sexual function as well as other areas that depend largely on healthy circulatory status.

L-arginine was first isolated in 1886. In 1932, L-arginine was found to be required for the generation of urea, which is necessary for the removal of toxic ammonia from the body. In 1939, L-arginine was also shown to be required for the synthesis of creatine. Creatine degrades to creatinine at a constant rate, and is cleared from the body by the kidney. Arginine is also a precursor of guanido-phosphate, phosphor-arginine and creatine, the high-energy compounds found in muscles. L-Arginine has been used extensively by bodybuilders to increase blood flow to muscle tissue and to enhance creatine storage in the body although recently Arginine Alpha-ketoglutarate has become more popular. Arginine is also an important factor in muscle metabolism and works to transport, store and excrete nitrogen