Caffeine is the most widely used drug in the world; nearly 100 percent of adult men and (non-pregnant) women report some level of caffeine consumption. Due to its widespread availability and use, both socially and as an ergogenic aid, caffeine was removed from the list of banned substances.
While numerous athletes attest to it's performance enhancement, many athletes, as well as the popular media believe that as the thermometer rises, caffeine becomes more hindrance than aid. However, caffeine's detrimental impact on heat tolerance, hydration and thermoregulation are unfounded by the current scientific studies.
Caffeine as an Ergogenic Aid
Caffeine, a naturally occuring trimethylxantine found in a variety of plants, is generally accepted by most sports scientists as an effective ergogenic aid. Its stimulating effect on the central nervous system (CNS) 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 (Åstrand et al., 2003). Caffeine is believed to enhance fat utilization in the body and has also been shown to effectively increase time to exhaustion during endurance activities, as well as sprint, power and strength performance.
The data, however, indicates that improved performance is typically in the pressence of current or prior strenuous activity. Put another way, caffeine seems most effective in restoring high intensity performance rather than enhancing it, which is a good thing for endurance athletes.
How much improvement can you gain from caffeine? This depends on many factors, including:
- duration and intensity of the activity
- how much caffeine you ingest
- when you take it
- whether you are a habitual caffeine user
In an extensive review recently published in the Journal of Strength and Conditioning Research, 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 perfomance assessement. 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 mg.kg-1 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, as substances in coffee may diminish caffeine's overall effects
- Habitual caffeine users may need to abstain at least seven days prior to competition to optimize its effects
Caffeine and Thermoregulation
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 nutrtional intake data from the U.S. Academy of Sciences, the typical American consumes more than enough compensate for these losses.
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. (2008) 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 as the best strategy for their own sport.