Arginine & Citrulline

L-arginine plays a role in building protein. The body uses protein to help build muscle and rebuild tissue. L-arginine helps with muscle growth because its presence is needed for the synthesis of most proteins. When the size of a muscle increases, L-arginine sends a signal to muscle cells, which encourages the release of growth hormone and aids in fat metabolism.

Unlike other amino acids, citrulline doesn't build proteins. Instead, it plays an important role in the urea cycle, helping your body to get rid of harmful substances, particularly ammonia. It also plays an important role in widening your blood vessels and in muscle building.