Supplements that work: Caffeine, the ergogenic aid

The following article was previously published by myself through I have made several updates to the article, however, that relate to the current body of knowledge on caffeine and endurance performance. If you’d like to listen to original Tipcast on this topic click here.

Caffeine is the most widely used drug in the world with nearly 100 percent of adults reporting some level of caffeine consumption, which is not surprising considering how many products contain caffeine. Caffeine was removed from the list of banned substances largely due to its ubiquity. It is the everyman’s ergogenic aid, yet, it still carries with it a stigma as well as many unfounded claims about its safety and effectiveness. This article will hopefully unravel many of those caffeine myths.


Caffeine is a naturally occurring trimethylxantine found in a variety of plants, is generally accepted by most sports scientists as an effective ergogenic aid. The leading candidate for this enhancement is caffeine’s stimulating effect on the central nervous system (CNS), which reduces the sensation of fatigue, perception of work effort and even pain. Moreover, caffeine improves mental acuity, focus and technical skill during and after strenuous activity or fatigue (Goldstein 2010). For many years, it was believed that caffeine enhanced fat utilization in the body, however, this has never been shown convincingly (ACSM Annual Meeting, 2010). Nonetheless, recent evidence, does indicate that caffeine does alter substrate use, particularly an increase in the uptake of ingested carbohydrate.

In a 2005 paper in the J. Appl. Physiol., Yeo and colleagues  compare the impact of a placebo, carb solution and carb + caffeine (~360 mg/hr) on cycling performance in trained cyclists. The overall findings were that performance was highest in the carb + caffeine group, which also showed the lowest use of fat and highest use of carbohydrate. They surmised that caffeine enhances the uptake of carbohydrate from the intestine and into the cells. Further research supports the use of caffeine with or without carbohydrate. Most recently, Lane and colleagues (including leading researchers John Hawley and Louis Burke) showed that 3 mg/kg weight of caffeine improve time trial performance above placebo. Even more surprising, was that beet root juice failed to improve performance, nor did its combination with caffeine prove more effective than caffeine alone. Finally, there appears to be little difference between caffeine powder or coffee of similar dosages. One more reason for that cup of joe on race morning.

In summary, the research strongly supports the use of caffeine to improve performance. In an extensive review by Ganio et al. (2009) examined 21 high previously published performance studies on caffeine that were considered high quality; all of the studies used either runners, cyclists or swimmers and a final time trial component, which has been shown to be most reliable and valid for performance assessment. These studies suggested that caffeine tended to improve endurance, but its effects varied greatly, possibly due to the factors mentioned earlier. Taking all of the available literature into account, and assuming you are accustomed to using caffeine already the following recommendations can be made in regards to caffeine:

  • Time ingestion to no more than 60 min prior to activity, and continuing use during competition seems most effective
  • Moderate quantities (3 – 6 body weight) has been shown to be most efficacious in athletes
  • Consuming caffeine either in pill form or in a carbohydrate beverage seems most effective, but there appears no difference in coffee vs caffeine impact.
  • Habitual caffeine users have been advised in the past to abstain at least seven days prior to competition to optimize its effects, however the current body of research, as well as expert recommendations no longer support this.


In an ironic twist, the widely held belief that caffeine acts as a diuretic has prompted many professionals to advise against consuming caffeinated products prior to exercise–particularly when the environment is hot. There is also an assumption that diuresis may compromise thermoregulation and promote exercise-induced cramps. However, scientific data does not support these notions.

In a 2007 review, Amstrong et al. (2007) compiled a review of 30 previous papers to assess the diuretic effect, electrolyte excretion and thermal regulation influence during exercise. They concluded that caffeinated drinks can make up a substantial part of one’s daily fluid intake and that those beverages appear no more diuretic than tap water. In reviewing several exercise studies using caffeine dosages as high as 600 mg, caffeine had no substantial effect on diuresis either at rest or during exercise. In regards to excretion of sodium and potassium, the data shows that caffeine can increase excretion of these electrolytes. However, based on nutritional intake data from the U.S. Academy of Sciences, the typical American consumes more than enough compensate for these losses. Finally, and most significantly, a very recent paper showed that regular coffee consumption has no detrimental impact or increased diuresis, hopefully burying this myth once and for all.

Regarding caffeine’s overall affect on thermoregulation, the available data on runners, cyclists and walkers in moderate to hot environments all agree that caffeine intake has no significant influence on thermoregulation. The authors conclude that “…restricting dietary intake of caffeine is not scientifically or physiologically supported.” While not specifically addressed in their review, it is also implausible that caffeine ingestion plays any role in cramping. While the mechanisms for exercise associated muscle cramping (EAMC) are still poorly understood, a review by Schwellnus et al. (2009) found no strong links between EAMC and either dehydration, environmental heat, or electrolyte imbalances. However, they did indicate that increased exercise intensity predisposed one to cramps.

As a coach and performance consultant, I am often asked to evaluate various training and nutritional strategies–including caffeine. Most athletes are looking an edge, but the line between science and hype is often blurred. Based on the available literature and my own experience, I’ve found that caffeine can be an effective performance aid in both training and competition. However, it is the responsibility of every athlete to understand how they respond to any supplement, as well as the best strategy for their own sport.

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