Caffeine, neuromuscular function and high-intensity exercise performance.

Caffeine is one of the most widely consumed drugs in the world. There is a strong belief that caffeine is an ergogenic aid to sports performance. Although much evidence suggests that caffeine may improve endurance exercise performance, questions still remain with regard to its effects on neuromuscular function and brief, high-intensity exercise performance. At the cellular level, caffeine stimulates the central nervous system (CNS), enhances neuromuscular transmission and improves skeletal muscle contractility. The former two effects seem to have facilitative effects on activities which require quick reactions and rapid movements. This is evident in that simple and choice reaction and movement times are reduced following ingestion of small quantities of caffeine. It appears, however, that the caffeine-induced increases in muscle contractility seen in vitro do not translate into improved strength, in vivo. Acute caffeine ingestion does not seem to increase maximal voluntary contractions or maximal power output nor delay fatigue. Thus use of caffeine to improve performance in activities requiring strength and short-term endurance seems unwarrented. Further research is needed before clear conclusions can be draw regarding caffeine's effects on neuromuscular function and high-intensity exercise performance.