Stimulants are substances that have a direct effect on the central nervous system. They increase the excitation of the brain and the body.

Adrenalin is an example of a naturally occurring stimulant in the body. The most commonly used stimulants in sport are amphetamines, cocaine, ephedrine and caffeine.

Stimulants are used by athletes to attain increased alertness, reduce tiredness and to increase competitiveness and aggression.

They can also help athletes exercise more strenuously and become less sensitive to pain.

Effects of stimulants

Stimulants can cause problems with the body's ability to regulate its temperature, meaning that the body may become overheated. They can also stop the heart and other vital organs from working properly. Other problems include:

-Loss of appetite
-Loss of sleep (insomnia)
-Reduction of fatigue resulting in exhaustion
-Body trembling
-Restlessness, agitation, tension
-Palpitations and heart rhythm disorders