The active ingredient in nitric oxide (NO) supplements is L-arginine, a non essential amino acid, made naturally in the body.  It is usually sold as arginine alpha keto-glutarate (A-AKG) and arginine keto iso-caproate (A-KIC).  This amino acid is necessary for the normal function of the pituitary gland.  Along with ornithine, phenylalanine, and other neurochemicals, arginine is required for the synthesis and release of the pituitary gland's growth hormone.

Arginine is an amino acid that is readily converted to NO in the body.  NO is a gas that is involved in vasodilation, which is the process that increases blood flow to muscles, allowing better delivery of nutrients and oxygen.  The idea behind the NO boosting supplements is to use L-arginine, A-AKG and A-KIC to increase the production of NO to bring greater influx of nutrients and oxygen to the muscles, causing a better pump when lifting weights, and increased recovery and muscle growth.