The Potential Negative Effects of Arginine and Caffeine in Pre-Workout Nitric Oxide Products

Nitric oxide is a chemical signaling molecule in the body involved with communication in the nervous, immune, and vascular systems. It was proclaimed the “Molecule of the Year” in 1992 by Science magazine because it is essential for the normal functions of the brain, arteries, immune system, liver, pancreas, uterus, nerves and lungs, to name a few. However, nitric oxide has both positive and negative influences on the body depending on which of the three nitric oxide enzymes or synthases are expressed. The three Nitric Oxide Synthase (NOS) isomers are Neuronal NOS (nNOS), Inducible NOS (iNOS), and Endothelial NOS (eNOS). nNOS is used to optimize brain focus and muscle contraction. iNOS activity promotes inflammation and produces harmful free radical actions. eNOS activity produces dilation of blood vessels, glucose uptake, and activation of muscle mitochondria energy utilization. To put it simply, nNOS and eNOS support ideal exercise physiology, whereas iNOS promotes muscle and joint inflammation and breakdown. Ideal NOS expression for enhanced muscle growth, contraction, and workout recovery would require greater eNOS and nNOS activity and suppressed iNOS activity. Additionally, increased iNOS activity would increase susceptibility to injury, diminished force generation, and muscle wasting.