Central nervous system stimulants

Three major types of CNS stimulant are currently abused in sport: amphetami ne, cocaine and caffeine. Each drug type has its own characteristic mechani sm of action on CNS neurones and their associated receptors and nerve termi nals. Amphetamine is widely abused in sports requiring intense anaerobic ex ercise where it prolongs the tolerance to anaerobic metabolism. It is addic tive, and chronic abuse causes marked behavioural change and sometimes psyc hosis. Major sports abusing amphetamine are cycling, American football, ice -hockey and baseball. Cocaine increases tolerance to intense exercise, yet most of its chronic effects on energy metabolism are negative. Its greatest effects seem to be as a central stimulant and the enhancement of short-ter m anaerobic exercise. It is highly addictive and can cause cerebral and car diovascular fatalities. Caffeine enhances fatty acid metabolism leading to glucose conservation, which appears to benefit long-distance endurance even ts such as skiing. Caffeine is also addictive, and chronic abuse can lead t o cardiac damage. Social abuse of each of the three drugs is often difficul t to distinguish from their abuse in sport.