Caffeine is a stimulant that is consumed by the majority of the world's population. Although some evidence has shown that caffeine improves athletic performance, the World Anti-Doping Agency has deemed it an allowable substance in sports competition. Research has explored various aspects of caffeine's effects on exercise performance to gain a clear understanding of how it works.
Endurance
A study published in 2010 in the "European Journal of Applied Physiology" sought to determine the precise effects of caffeine on athletic performance, including oxygen uptake, also known as VO2 max; oxygen deficit; and certain substances that are by-products of exercise. The researchers evaluated six trained cyclists who exercised to a level beyond aerobic capacity -- the ability of the body to utilize oxygen -- following consumption of 5 mg per kilogram of body weight of caffeine. There was a significant increase in exercise endurance and the ability of the athletes to exceed aerobic capacity; however, no change was observed for maximum oxygen uptake. Blood potassium levels were tested as a measure of metabolic efficiency and found to be decreased after caffeine consumption and prior to exercise, leading the researchers to suggest the possibility that caffeine had a conserving effect on potassium, thereby prolonging time to fatigue.
Time Trials
Citing the lack of real-world athletic competitions that test endurance alone, in the absence of time or distance limits, an analysis of studies on the effect of caffeine in time trial athletic competitions was published in 2009 in the "Journal of Strength Conditioning Research." In a time trial, the best effort is measured over a set distance or time limit. The meta-analysis reported as much as 17 percent improved performance with moderate consumption of 3 to 6 mg per kilogram of body weight of caffeine. The researchers also noted that abstaining from caffeine for seven days prior to a competition produced the best performance results.
No Effect
A study on 100-km cycling time trials found caffeine ineffective at improving performance outcome. The study, published in 2002 in the "International Journal of Sports Nutrition, Exercise and Metabolism," gave eight highly trained cyclists 6 mg per kilogram of body weight of caffeine 60 minutes prior to starting one of three cycling trials, with additional maintenance doses of 0.33 mg per kilogram every 15 minutes during the event. The researchers measured average power and time to completion, and reported there was no difference between trials with and without caffeine. Additionally, the study found that while heart rates were higher in the caffeine group, no significant differences in EMG amplitude -- a measure of the strength of nerve conduction to the muscles -- and no difference in power output were observed, leading the researchers to conclude a central nervous system control center involved in exercise performance is not affected by caffeine.
References
- PubMed.gov: Caffeine improves supramaximal cycling but not the rate of anaerobic energy release
- PubMed.gov: Effect of caffeine on sport-specific endurance performance: a systematic review
- PubMed.gov: Caffeine ingestion does not alter performance during a 100-km cycling time-trial performance
- AllBusiness: Athletes can take caffeine
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