Arginine

Several years ago, supplements that are purported to elevate nitric oxide production in the body became popular among those seeking muscle growth and strength gains. Blood vessels produce nitric oxide, which helps them dilate to increase blood flow. With increased blood flow comes increased oxygen and nutrient delivery to the muscles and fuller, more “pumped” looking muscles. The amino acid arginine is one of the main substrates for nitric oxide synthesis. Arginine supplementation has been shown to increase nitric oxide production, and it is the main ingredient in most of the many NO2 boosting supplements on the market.

The majority of these supplements are marketed with claims that they increase muscle size and strength. However, there is absolutely no scientific basis for either of these claims. In fact, arginine supplementation has been shown to mute the growth hormone response to resistance training, making it more likely to limit mass and strength gains than to augment them.