WHAT IS ARGININE? L-arginine is a protein amino acid present in the proteins of all life forms. It is classified as a semi-essential or conditionally essential amino acid that promotes protein synthesis in the recovery from exercise. HOW DOES ARGININE WORK? Arginines works in the body by being key to efficient muscle metabolism because of its role in the transport, storage, and elimination of nitrogen. Creatine is derived from arginine, as are guanidophosphate and phosphoarginine, all of which have roles in muscle metabolism. Arginine also promotes protein synthesis, which combined with resistance training causes an increase in muscle growth. HAVE YOU EVER HAD HEART PROBLEMS? It is recommended that anyone who has had heart complications of any kind talk to their doctor before using arginine.