Nitric oxide (NO) is a naturally occurring free radical in your body that supplement companies are claiming can actually boost your workout performance. Those looking to increase muscle mass are drawn to the claims that NO can enhance workout performance, increase stamina and promote muscle repair. Sounds like a magic little pill, but is it too good to be true?
As a vasodialator, NO expands the veins to lessen the force the heart must exert to pump the same amount of blood through the body. Since oxygen is carried in the blood, elevated levels of nitric oxide are said to enhance oxygen delivery to your muscles. NO boosters are being marketed as great way to improve your workout performance. The primary ingredient in NO boosters is arginine, and these supplements, typically sold in pill form, usually contain additional active and inactive ingredients.
The effects of nitric oxide on muscle growth and development are under investigation in the scientific community, but there are many studies that have given us a bit of insight. In a study performed by the International Journal of Sports Medicine 30 endurance athletes were given L-arginine, aspartate or a placebo. At the end of the study, evidence showed zero increase in endurance and blood vessel dilation in participants, and that nitric oxide does not promote muscle growth.
Another study from the Baylor University (Texas) examined the effects of arginine supplements during training on body composition in experienced exercisers. At the end of the trial, no significant differences were observed in participants’ body mass, fat mass or body fat percentage.