Friday, December 11, 2009

Does caffeine enhance athletic performance?

The fruit seed coffee beans are the mainstay of many countries economic sustainability. Furthermore, most people (52% of Americans including myself) depend on coffee for their energy daily. The popularity of caffeine is no foreign concept to athletes either. Most gu's and gels contain caffeine and I hear more and more people trying 5 Hour Energy Shots before competition and games, not to mention the $5.4 billion dollar industry of energy drinks. But is all this hype about caffeine hearsay, or is it worth downing a mug of joe before your next marathon?

Caffeine works similarly to other addictive drugs, say nicotine and cocaine, by blocking adenosine receptors. Caffeine crosses the blood-brain barrier and actually blocks blood flow by about 22-30%, thus blocking pain and decreasing feelings of fatigue. Metabolites of caffeine such as theobromine increase the amount of oxygen and blood flow to muscles and theopylline acts as a muscle relaxant that targets bronchioles (our lungs).

Caffeine's important mechanism of action as far as athletes are concerned comes with its ability to spare muscle glycogen. Glycogen is the stored form of glucose, our body's preferred source of fuel, in the liver and muscles. Experimental studies have not reached a consensus on this puzzle, but some point to caffeine elevating free fatty acids in the blood, thus allowing the body to use fatty acids as energy instead of carbohydrates. Caffeine also impacts the enzymes that break down glycogen, thus sparing the glycogen. Calcium release is necessary for muscle contraction, and since caffeine stimulates this release, it has a direct affect on muscle fatigue.

Caffeine's effects can be felt after 30 minutes of consumption and stay within the system for 4-6 hours. Actually, if you consume an afternoon latte, by bedtime only half of the caffeine has been metabolized and left your bloodstream. A good point to keep in mind if are interested in keep your sleeping habits regular, especially for training purposes. Although you may be able to fall asleep without problem, caffeine will interupt your sleep cycle and the quality of your sleep.

Overall, experts do claim caffeine consumption to be advantageous for athletic performance. Benefits are reached when more than 3 mg caffeine per kilogram body weight is consumed, with max benefits around 6 to 9 mg/kg body weight. For a point of reference, a 12 ounce mug (the size of a tall Starbucks beverage) of drip coffee contains about 200 mg caffeine. Generally speaking, gu's have 20-30 mg caffeine per packet.

Additionally, benefits of caffeine are noticed more when caffeine is consumed both before (no more than 60 minutes) and during activity, 4.3 ± 5.3% better actually. Studies also show that dehydration is not necessarily more worrisome with caffeine ingestion but that caffeine's benefits are better felt with water and carbohydrate consumption.

Caffeine still can benefit even us chronic users, but habitual caffeine drinkers will have more adenosine receptor sites, making caffeine's work a little more difficult. It may be best to abstain from caffeine up to seven days before the sporting event to feel the maximum effects the day of.

I actually participated in a study conducted by the University of Illinois that sought to determine the affects of caffeine on athletic performance. On two separate occasions, I ingested a pill - one caffeinated capsule and one placebo. There was a noticeable difference in my cycling effort. Although I am not a cyclist, I was able to exert myself to a much greater effort on the 2nd attempt. I can only assume this was after having the caffeinated capsule considering the results of the study showed that caffeine does in fact reduce leg muscle pain, allowing a greater cycling intensity because of blocked pain receptors. Titled "Effect of Caffeine on Leg-Muscle Pain During Intense Cycling Exercise," this study was published in the International Journal of Sport Nutrition and Exercise Metabolism.

How bout those 5 Hour Energy drinks? Although they do not contain the sugar of most other energy drinks, they are mostly caffeine (~138 mg) with a megadose of B vitamins and some amino acids. Amino acids can enter the Krebs cycle, the second part of ATP production. B vitamins are necessary for the metabolism of carbohydrates and proteins, thus helping with the conversion of carbs to glucose, giving us more energy. Side effects of too much B6 include nerve and muscle damage


Judelson, DA, Armstrong, LE, Sokmen, B, Roti, MW, Casa, DJ, and Kellogg, MD. Effect of chronic caffeine intake on choice reaction time, mood, and visual vigilance. Physiol Behav 85: 629-634, 2005.

O'Connor, PJ, Motl, RW, Broglio, SP, and Ely, MR. Dose-dependent effect of caffeine on reducing leg muscle pain during cycling exercise is unrelated to systolic blood pressure. Pain 109: 291-298, 2004.

Ganio, Matthew S; Klau, Jennifer F; Casa, Douglas J; Armstrong, Lawrence E; Maresh, Carl M. Effect of Caffeine on Sport-Specific Endurance Performance: A Systematic Revie. Journal of Strength and Conditioning Research 23(1), 315-324, 2009.

Clark, N. Sports Nutrition Guidebook 3rd Edition. Champaign: Human Kinetics; 2003: 102-103.

Ryan, M. Sports Nutrition for Endurance Athletes 2nd Edition. Boulder, Colorado: Velo Press; 2007: 197.

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