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Nutrition Column

Enhancing Performance with a Cup of Coffee, or Two

Many people begin their day with a cup of coffee to simply “get them going,” however many athletes consume coffee as an ergogenic aid to enhance their physical performance. The main component of coffee responsible for its enhancing effect is caffeine, a psychoactive stimulant of the central nervous system. An ergogenic aid is anyexternal influence that positively affects an athlete’s mental or physical performance by directly enhancing physiological processes. Caffeine molecules bind to adenosine receptors in the CNS, and block the binding of adenosine, which results in a decreased adenosine effect. This then stimulates the release of a chemical called dopamine that has been shown to increase heart rate and could be responsible for part of caffeine’s stimulatory effect. Caffeine also inhibits an enzyme involved in the break down of lipid molecules to glycerol and fatty acids, which can both be used to fuel muscles. Studies have suggested that the body adapts to frequent consumption of caffeine, lessening its stimulatory effect. Therefore an athlete’s tolerance of the drug becomes important when caffeine is being used as an ergogenic aid.

A study published in the Journal of Applied Physiology investigated the difference in the duration of caffeine’s ergogenic effect between frequent consumers (users) and nonusers of the drug. Subjects consumed 5mg/kg body weight of caffeine or placebo and were asked to perform a ride to exhaustion at 80% VO2 max, 1, 3 and 6 hours after ingestion. Blood samples were taken and plasma levels of caffeine and free fatty acid were measured to see if the duration of caffeine’s ergogenic effect was related to the circulating concentration of the drug. A 5mg/kg body weight dose of caffeine, which is about 2 cups of coffee for a 150 lb individual, significantly improved all subjects’ time to exhaustion. The increase ranged from 24-28 minutes on average; however the ergogenic effect was greater in nonusers and still evident 6 hours after ingestion of the drug despite decreased levels of caffeine in circulation.

The researchersfrom the study suggest that as the body adapts to frequent caffeine consumption, the numbers of adenosine receptors is increased therefore requiring higher blood concentrations of the drug to block the same percentage of receptors. This explains the shorter duration of the ergogenic effect seen in users. They concluded that the ergogenic effect of caffeine is greater and longer lasting in nonusers when compared to users, emphasizing the importance of considering an individual’s sensitivity to caffeine when determining the optimal dose and time framefor enhanced performance.

Written by Jodie Sasaki with Eric Sternlicht, Ph.D. Occidental College, Los Angeles, CA.