Race Fueling

Sports Science Update: Caffeine’s Effect On Time-Trial Performance

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To what extent does caffeine aid in athletic performance? Tim Mickleborough turns to science in an attempt to answer this question.

Written by: Tim Mickleborough, PhD

Caffeine is probably the most widely used pharmacologically active substance in the world. Although caffeine is found in a number of foods, it is most frequently consumed in coffee, tea and cola beverages. In January 2004, the World Anti-Doping Agency (WADA) removed caffeine from its restricted substances list. Consequently, athletes are now able to consume caffeine in conjunction with WADA-sanctioned sports, without fear of doping code violations. However, caffeine remains on WADA’s monitoring program, indicating that the drug is placed under heightened scrutiny for further tracking of trends in use and possible abuse that could ultimately place it back on the banned list.

Photo: Robert Murphy
Photo: Robert Murphy

To date, the majority of research on caffeine in sport has focused on its potential ergogenic (i.e. performance-enhancing) properties. More than 80 original studies have been published in peer-reviewed journals documenting caffeine’s effect on various aspects of sporting performance.

The ergogenic effect of consuming caffeine on endurance exercise performance is now well recognized. It has been shown that relatively high amounts of caffeine—about 350 mg, or roughly three cups of coffee—significantly improve endurance exercise performance, and that simultaneous ingestion of glucose may provide an even greater enhancement in performance. Studies have shown that gastrointestinal absorption of glucose is enhanced when low doses of caffeine (1.35 – 5.00 mg/kg) are co-ingested with carbohydrate during exercise in previously fasted subjects. The ingestion of 350 mg of caffeine, though, would likely exceed what an athlete typically ingests before exercise.

Thus, Desbrow and colleagues1 recently performed a study designed to investigate the influence of low to moderate doses of caffeine ingestion on cycling time-trial performance and carbohydrate oxidation in fed subjects. To their surprise, neither the low (~125 mg) nor the moderate (~250 mg) dose of caffeine caused an increase in time-trial performance or fuel metabolism.

Importantly, the subjects in this study exercised in a non-fasted state and were allowed to consume a carbohydrate solutions whenever they wished during the time trial. Thus, the results suggest that caffeine’s ergogenic potential might change based on exogenous carbohydrate availability. This means that when carbohydrates supplied by an external source such as a sports drink is moderate, caffeine has the potential to increase carbohydrate absorption and usage by the muscles, thus potentially enhancing performance. However, when athletes are supplied with ample carbohydrates before or during exercise, caffeine might have no additional effect.

What does this mean for you? Since you would never wish to take in less than the optimal amount of carbohydrates before or during an event, the study by Desbrow et al. could be taken to imply that you should not bother to consume caffeine in events where carbohydrate availability is not limited for you.

However, athletes should be cautioned against this and instead wait for more studies to confirm the findings of the Desbrow study, which has a couple of important limitations. First, it lacked a high-caffeine dose group. Also, it failed to distinguish between habitual and non-habitual caffeine users, which is important, as past research has shown that habitual caffeine use kills its ergogenic potential.

Dr. Mickleborough is an associate professor of exercise physiology at Indiana University. He is a former elite-level athlete who placed 18th overall (8:55:38) and second in the run (2:52:13) in the 1994 Hawaii Ironman World Championship. Contact him at Speedlab@juno.com.


1. Desbrow, B., C.M. Barrett, C.L. Minahan, G.D. Grant, and M.D. Leveritt. “Caffeine, cycling performance, and exogenous CHO oxidation: a dose-response study.” Medicine & Science in Sports & Exercise, 41, 9 (2009): 1744-1751.