Performance-enhancers are substances that some athletes take into their bodies with the hope of improving their athletic performance or getting an edge over the competition. There are two main categories of performance-enhancers: steroids and nutritional supplements. 

• Steroids (Anabolic) are synthetic versions of hormones that mimic testosterone, one of the body's natural chemicals. Testosterone is one of the main hormones that build and strengthen muscles.  Doctors prescribe steroids to build up muscles in very sick patients. This is because their muscles have wasted away. Some athletes use steroids illegally to build muscle mass. 

• Nutritional Supplements are substances, which occur naturally in foods. Some athletes take larger amounts of these substances, which usually are concentrated in the form of pills or powders, seeking to improve their performance on the field.