Monday, March 24, 2008

Is Caffeine an Effective Ergogenic Aid?

Energy drinks have become widely popular in the athletic community. In past years, ingestion was limited to coffee, tea and, to a lesser extent, soda. Since most young athletes don’t care for coffee or tea, their use of caffeine was limited. More recently, however, the introduction of so called “energy drinks” have widened the access to caffeine. Sales of energy drinks have increased and more as more brands appear on store shelves. Much of the popularity of these drinks lies in their caffeine content. This raises an important question, does caffeine improve athletic performance? The answer is yes and no along with several words of caution.

In the scientific community, there is considerable debate as to whether or not caffeine is a true ergogenic aid. A number of factors make caffeine research sometimes difficult to interpret. These include individual tolerances to the drug, the doses of caffeine used and the type of activity studied. Nevertheless, there is evidence to suggest that caffeine may aid some types of performances but hinder others. There is also considerable evidence that dependence on caffeine as a method improve performance my ultimately lead to long-term decrements in both performance and overall health, particularly in the young athlete.

Caffeine is one of the most widely consumed drugs in the United States. It is found in a number of foods and beverages. A typical cup (5oz) of coffee may contain 75-150mg whereas some soft-drinks (12oz) and chocolates (1oz) may contain 25-60mg caffeine. Caffeine is also found in several over-the-counter analgesic, stimulant and cold/allergy drugs (30-200mg). Newly formulated “energy drinks” contain substantial amounts of caffeine. A 16oz energy drink contains about 140-170mg. Other energy drinks may contain well over 300mg. Also new energy mints and gum contain caffeine ranging from about 5-40mg per piece. It is easy to see that caffeine is widely available in a variety of forms and can be purchased just about anywhere.

Caffeine is classified as a central nervous system (CNS) stimulant and is often used to increase arousal and alertness and to offset mental and physical fatigue. It also affects the cardiovascular, pulmonary and neuromuscular systems. A number of athletes and coaches consider caffeine to be an ergogenic aid. That is, its use may improve athletic performance. Caffeine was first place on the International Olympic Committee (IOC) banned substance list in 1962, removed in 1972 then added it back in 1984. However, the urinary levels of caffeine required for disqualification were excessive, probably gained only through the use of injections and suppositories. In 2003, the World Anti-Doping Agency (WADA) removed caffeine as a prohibited substance, considering it only a “mild stimulant”. Thus caffeine consumption as an ergogenic aid must be considered legal.

Caffeine's effects on the neuromuscular system and on activities of short duration are somewhat confusing. Laboratory studies on isolated muscle tissue suggest that caffeine increases muscle strength. However, the effective concentrations used in these animal studies were some 100-500 times higher than blood levels found in humans even after excessive caffeine consumption. In our laboratory, we have found that caffeine ingestion (~300mg) has virtually no influence on muscular strength or power. On the other hand, caffeine decreases reaction and movement times due to its arousal effects on the CNS. This might prove beneficial in sports in which rapid reactions to a starter’s pistol or an opponents movements are important. However, while caffeine improves reaction time, it has negative effects on control of fine movements. It markedly reduces hand steadiness and can severely affect fine motor skills and precise movements. This could lead to reduced performance in activities such as shooting or archery where steadiness and fine movement control are important.

An additional effect of caffeine consumption is on selection of fuel utilization during prolonged exercise. In general, muscle uses two substrates for energy production - glucose and free fatty acids (FFAs). Glucose is found in the blood and stored in the liver and muscle as glycogen. FFA’s are stored in fat depots in various locations. In endurance events lasting more that 120min, performance tends to be limited by the availability of muscle glycogen and blood glucose (see post titled Tournament Time – Nutritional Strategies). As muscle glycogen levels decline, blood glucose drops and performance markedly deteriorates. Caffeine releases FFAs from fat tissue into the blood which results in greater use of FFA by the muscle. This, in turn, tends to spare muscle glycogen and helps maintain blood glucose so that performance is less affected. Several studies have shown that moderate caffeine consumption (250mg) can increase exercise duration and may lower times in endurance events such as running, cycling and swimming. Thus, in regards to long-term endurance performance, caffeine may be beneficial.

As for soccer, there are few studies of the effects of caffeine on performance. It is unlikely that the duration and intensity of a youth match are great enough to take advantage of the glycogen sparing effects of caffeine. It is entirely likely that proper pre-match and post-match recovery diet would overshadow any potential benefits of caffeine. Similarly it is not at all clear if caffeine’s CNS effects enhance or hinder technical ability. One could argue that caffeine effects on focus and attention could prove beneficial. However, anxiety, lack of steadiness and fine motor control could be detrimental. In the only study that has specifically focused on soccer, caffeine was found to increase muscle stress and augment the risk of muscle damage. Thus, at this point, it is difficult to say with any degree of confidence if caffeine will improve, have no effect on or hinder soccer performance.

Several words of caution are needed concerning the use of caffeine as an ergogenic aid. First, caffeine has numerous side effects. It can cause severe anxiety and nervousness, both of which can dramatically impair performance. It may induce gastrointestinal discomfort and can result in cardiac arrhythmias and elevated blood pressure. Caffeine is also a powerful diuretic that can trigger the need to urinate repeatedly. It can also raise the risk of dehydration particularly during matches on hot days. For healthy adults, these side effects are often not life-threatening but can be. More importantly, there is no research into these types of side effects in children or adolescents. It is quite possible that some young athletes may be more susceptible to cardiovascular complications and dehydration. As for performance, these complications can make the athlete quite uncomfortable and may render him or her unable to compete. Anxiety, stomach pain and dehydration can easily outweigh any benefits.

Second, individual responses to caffeine are remarkably variable. The amount of caffeine which improves performance in one individual may result in deleterious side effects in another. Also, tolerance to caffeine's effects is found in chronic users. The more the athlete consumes, the more he/she may need to improve performance.

Finally, the use of any substance as an ergogenic aid raises important health and ethical issues. It is well known that caffeine can be addictive. This reliance on caffeine can be both physiological and psychological (the so-called placebo effect). Headaches, fatigue, irritability and nausea can occur in caffeine-dependent individuals when they do not have access to the drug. Also an athlete who takes caffeine and has an outstanding match may soon feel that caffeine is required in order to compete. Without it, performance will suffer. Using caffeine to enhance performance can lead the athlete down a slippery slope towards both physiological and psychological dependence. One must remember that in many cases, the short-term, positive benefits of caffeine might very well be outweighed by the negative side effects.

As for a recommendation, youth players should avoid the use of caffeine as an ergogenic aid. The adverse side effects and health risks associated with repeated use clearly outweigh any possible benefits. Further, the potential of both physiological and psychological dependence far exceed and short-term gains that caffeine my cause.

Because caffeine is widely available, it is imperative that both the athlete and coach fully understand the risks and benefits to both the individual's well-being and their athletic performance. Although caffeine is a naturally occurring substance and is found in many common foods and beverages, it is a very potent drug and should always be treated as such.

References:

The Mayo Clinic. (2007). Food and nutrition: How much caffeine is in your daily habit?” Mayo Clinic, http://www.mayoclinic.com/health/caffeine/AN01211.

Calfee R, Fadale P. (2006) Popular ergogenic drugs and supplements in young athletes. Pediatrics, 117:e577-e589.

Paluska SA (2003) Caffeine and exercise. Current Sports Medicine Reports, 4:213-219.

Schwenk TL, Costley CD (2002) When food becomes a drug: Nonanabolic nutritional supplement use in athletes. American Journal of Sports Medicine, 30:907-916.