Many of them use methods or agents to improve their energy and performance. These are called ergogenic aids.
Some aids can have harmful side effects.
They are banned by sports governing bodies because they are unsafe and unethical. Many side effects occur from abusing these steroids. Heart, liver, and immune system problems can develop. Men's testicles shrink, the prostate gland enlarges, and sperm levels drop. Behavior changes may include aggression, paranoia, mood swings, low sex drive, and depression.