Contributed by Dr. Steven T. Devor – Director of Performance Physiology for MIT and OhioHealth, and Associate Professor of Exercise Physiology, Department of Human Sciences, and Department of Physiology and Cell Biology, The Ohio State University

There is little question that caffeine is the most widely consumed drug in the world. Indeed nearly 100 percent of adult men and (non-pregnant or lactating) women report some level of caffeine consumption. Due to both the widespread availability and use of caffeine, both socially and as a performance enhancer, in 2005 it was removed from the list of banned substances by both the United States Olympic Committee and the International Olympic Committee.

It is true that many, though not all, endurance and strength athletes utilize caffeine as a performance enhancer. However, many athletes believe that as the thermometer rises caffeine consumption becomes more of a handicap than a performance enhancer. This belief has also been reported widely in the popular media.  But the negative or poor influence of caffeine on a.) your hydration status; b.) your bodies ability to thermoregulate; and c.) your overall heat tolerance is not supported at all by carefully controlled and published scientific studies.  

Caffeine is accepted by nearly all exercise physiologists as an effective and positive performance enhancing aid, and it has been studied extensively over the past 50 years in relation to athletic performance. We know caffeine has a stimulating effect on the central nervous system, which serves to lower your perception of how hard you are training or racing, reduce the sensation of fatigue one has while exercising, and even diminish feelings of pain. Caffeine has also been shown to enhance fat as a fuel source during exercise, and to increase the time to exhaustion for endurance athletes while training and racing. Finally, caffeine has been shown to improve the ability to focus and perform technical skills both during and after strenuous activity or fatigue.

The level of athletic performance enhancement you might expect to gain from caffeine consumption depends on a number of factors, which include:  a.) the duration and level of intensity of the activity you are engaged in; b.) what amount of caffeine you typically ingest on a daily basis; c.) when you consume the caffeine in relation to your training or scheduled race; and d.) if you are someone that uses caffeine daily.

When taking all of the current available published scientific literature into account and making the assumption you are already someone that has caffeine regularly, the following three recommendations should be followed to obtain the maximum endurance performance benefit:  

1.) Caffeine should be consumed no more than 60 minutes prior to training or racing, and using it during training or a race appears to make it the most effective.  Consumption during training or racing can be accomplished by utilizing performance beverages with caffeine, or gel packs/blocks/beans with added caffeine;

2.) The most effective amount of caffeine for performance enhancement appears to be 3 – 6 milligrams of caffeine per kilogram of body weight.  An 8 ounce cup of Starbucks coffee has approximately 150 milligrams of caffeine, and a 12 ounce Pepsi has approximately 40 milligrams of caffeine;

3.)  Athletes that ingest caffeine regularly will see the greatest performance benefit by not having any caffeine for 5 -7 days prior to a race.

The often publicized belief that caffeine acts as a diuretic and serves to dehydrate athletes has prompted many to advise against consuming caffeinated products prior to exercise, especially when the environmental conditions are hot and/or humid.  Inherent in this recommendation is a belief that the diuretic effect of caffeine will decrease the ability of your body to thermoregulate.  Once again, a careful review of the available published scientific literature does not support this recommendation.  There is simply no data to back up this belief.

A recent review of the caffeine and diuretic literature concluded that caffeinated drinks may comprise a large portion of your daily intake of fluids, and that caffeinated beverages appear no more significantly diuretic than tap water.  Several recent exercise studies that utilized dosages of caffeine as high as 600 milligrams per day (approximately four 8 ounce cups of Starbucks coffee), demonstrated that caffeine had no detrimental diuretic effect either at rest or during endurance exercise.  With respect to the caffeine-induced loss of sodium and potassium while exercising, the data shows that caffeine can increase excretion of these electrolytes.  However, based on the latest nutritional intake data from the U.S. Academy of Sciences, the average American consumes more than enough sodium and potassium in their typical diets to compensate for the caffeine-induced losses of these two electrolytes.

As an exercise physiologist and endurance athlete, I am frequently questioned about numerous training and nutritional plans for performance.  It is clear to me whether beginning or well seasoned, amateur or elite, endurance athletes are searching for aids that will improve their performances during training and racing situations.  Unfortunately, the line between what is scientifically known and what is hearsay and hype is often blurred.  With regard to caffeine, based on the available published scientific literature and my own experience, I believe caffeine can be a very effective performance aid in both training and competition.  Be advised though, it is the individual athletes responsibility to determine how they respond to any performance or nutritional aid, and then develop the most effective plan for themselves and their sport.

Dr. Devor

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