L-arginine is a potent amino acid that occurs naturally in the body. It works to produce nitric oxide (N.O.), the “miracle molecule” that helps relax blood vessels (known as vasodilation) and improve circulation, which leads to stronger blood flow.When it comes to athletic performance, stronger blood flow means better pumps when lifting weights, and thus an improved ability to build muscle. For sexual performance, enhanced blood flow means more excitement and more support when and where you need it most.