Nitric oxide is marketed to gym enthusiasts looking to train harder and build bigger muscles. When your body breaks down arginine, an amino acid, it forms nitric oxide, a gas, which then communicates between your cells. Supplements that boast "nitric oxide" on the label actually contain arginine -- which is found naturally in crab, meat, spinach and other foods. Although scientific studies are inconclusive on the benefits of using nitric oxide supplements for powerlifters, many athletes do take them in hopes that they will increase muscle pump, enhance recovery and increase work output.

Circulation and Oxygenation

Nitric oxide plays a role in blood circulation and in regulating brain, lung, liver, kidney and stomach function. Nitric oxide is also involved in the release of hormones, particularly adrenaline. Powerlifters take nitric oxide supplements to make the body more effective at carrying out these functions. Better circulation means faster and more efficient delivery of nutrients to working muscles when you’re lifting – so, theoretically, you’re able to lift heavier and participate in longer workouts.

Recovery and Pump

Taking nitric oxide supplements, along with ample protein and carbs post workout, is also supposed to help you recover more quickly. Increased circulation and more efficient organ function enables your cells to get the nutrients they need for rebuilding and repair faster. Nitric oxide is also said to increase the amount and duration of muscle pump -- the swelling the muscles experience after a hard workout. This pump is desirable to anyone who desires to appear "big" post-session.

Research Says

A few studies support these theoretical benefits of nitric oxide supplements. A 2006 issue of “Nutrition” found that when trained adult men took 12 grams of l-arginine alpha-ketoglutarate -- or AAKG, which is the scientific identification for nitric oxide supplements -- daily for eight weeks along with four regular resistance-training sessions per week, they experienced a significant improvement in their one-repetition maximum bench press and in aerobic power. The study did not show any effect of nitric oxide supplementation on body composition or aerobic capacity.

A later study, published in a 2008 issue of the “International Journal of Sports Nutrition and Exercise Metabolism” concluded that, when combined with the supplement Creatine, AAKG helped increase peak power and upper body muscle endurance.

Before You Supplement

Both of the aforementioned studies found no adverse health reactions to taking nitric oxide supplements. Still, you should always check with your doctor before adding supplements -- even over-the-counter ones -- to your diet. Researchers haven’t been able to make a recommendation as to appropriate dose, either. According to the website ExRx.net, 2 to 6 grams per day are the generally accepted temporary recommendations for AAKG. Supplement company recommendations may range from 3 and 30 grams per day.