Erythropoietin

This is a hormone that people with kidney disease use to ward off severe anemia. It increases red blood cells and the production of hemoglobin, which eases oxygen transferal to the muscles. Epotein, which is synthetic erythropoietin, is used by endurance athletes who must endure long treks or runs. Competitive bicyclists were big users of the hormone in the 1990s, before testing for it began. Overuse of the product can lead to heart attack, strokes or pulmonary embolisms.

Creatine

Used as a nutritional supplement rather than a performance enhancer, creatine is available in powder or pill form. The most popular version is creatine monohydrate.

Creatine is a natural compound produced in the body that helps muscles unleash stored energy. Research shows it leads to short-term bursts of power, ideal for sprinters or weightlifters. It does this by helping the body create more adenosine triphosphate (ATP). The liver normally produces two grams of creatine each day, and meat-eaters get a healthy dose of it in their diets.

Because creatine is stored in the muscles, it’s easy to reach certain levels of it. But it’s also easy for the kidneys to flush it, making its value questionable. Some research indicates it provides little to no benefit.

Side effects of creatine use include muscle cramps, weight gain and stomach cramps. In addition, using creatine may damage the liver and kidneys. While there are no studies yet on its long-term effects, it is still sold freely on store counters.

Whatever supplement or performance enhancer is used, keep in mind that changing the body’s chemistry always carries some risks. Talk to a doctor or licensed trainer before starting any hormone or drug regimen to determine safe levels. Many athletes cycle the treatments to preserve health.