Doping encompasses a wide range of medications, stimulants, and procedures. According to Dr. Chris Gordon, Assistant Director of the Utah Valley Sports Medicine Clinic, one of the most prevalent kinds is rising testosterone levels. Testosterone is an androgen (a male hormone) that helps build muscle and bone mass. At high levels, it can also give you more energy and make you feel happier. The most effective way to prevent doping is by prohibiting certain drugs from being used in sports. For example, caffeine has been shown to inhibit the effect of corticosteroids, which means that a cyclist who uses caffeine may be able to survive at higher doses of steroids than otherwise possible. The World Anti-Doping Agency (WADA) prohibits its members from testing for caffeine because it believes it is too difficult to do so accurately without breaking down the molecule structure of the drug. However, it is banned from competition due to its ability to reverse the effects of steroid use. In addition to medications, some athletes will choose to use supplements instead. These can include products such as erythropoietin (EPO), which stimulates blood production; human growth hormone (HGH); and testosterone/anabolic steroid preparations. All of these substances are designed to give an athlete an edge over their competitors. Finally, there are other methods used for cheating.