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Caffeine and Sports Performance

Jack Hartley



Introduction to Caffeine

Purpose of Caffeine in Athletics

How Caffeine works, in theory

Caffeine Controversy

Side Effects of Caffeine

Diuretic Effect

Tips for Athletes using Caffeine



Introduction to caffeine

          Caffeine is a mild stimulant that occurs naturally in at least 63 plant species.  Caffeine can be found in the leaves, stems, seeds, and roots of these various plants.  Caffeine is part of the methylxanthine family.  It consists of a xanthine molecule with three methyl groups attached to it.  Caffeine can be found in many products like sodas, tea, and coffee, but it also occurs in several other products such as prescription medications, diuretics, and pain relievers.  Caffeine’s widespread use and popularity have caused many people to view the substance as an addictive drug.  Thus making caffeine the most inexpensive and readily available drug known to man.  Then on the other hand there are people who view caffeine as a helpful stimulant that increases the individual’s concentration and awareness as well as many other physical traits.  The important thing to remember is that caffeine’s affects vary based on the person, the amount ingested, the frequency of consumption, and individual metabolism.  (


Purpose of Caffeine in Athletics

          Caffeine has many specific benefits for different types of athletes.  Though much of the research on caffeine in athletics is inconclusive, there are many athletes that believe the substance can enhance their physical as well as mental performance.  It is supposed that caffeine can improve the athlete’s endurance in sports where long-term stamina is needed.  These sports include cycling, running, and even soccer.  In an experiment to study the effects of caffeine as an ergogenic aid, 6 regular caffeine users were monitored while they exercised until exhaustion.  During this double blind, placebo test, the athletes were given pills an hour before the exercise trial.  The results were that those who received caffeine before the exercise performed more efficiently than those who received the placebo. (Graham, 1998)  This shows the importance of caffeine in endurance sports such as cycling, running, and soccer which require a great deal of physical stamina in order to compete successfully.  Studies also show that caffeine has very little affect on athletes requiring quick burst of energy such as sprinters and swimmers.  Also caffeine has been known to decrease fatigue in athletes, which plays a physical as well as psychological role in the performance of an athlete.

          Caffeine’s mental appeal is just as trendy as its physical purpose.  Caffeine has been proven to stimulate the central nervous system.  Caffeine stimulates the Central Nervous System at high levels, like the medulla and cortex, and even has the ability to reach the spinal cord in larger doses.  The effect of caffeine in the cortex is a clearer thought process and also can rid the body of fatigue.  This gives people a greater ability of concentration for 1-3 hours.  For athletes competing in sports where quick thinking and rapid reactions are necessary, caffeine can provide a huge edge.  However, these results are much more inconsistent than the experiments done on caffeine in endurance sports. (


How caffeine works, in theory

          In athletics three theories have been presented that support caffeine’s use in athletics.  The first theory focuses on caffeine’s ability to cause the body to burn more fat and fewer carbohydrates.  Glycogen is the principle fuel for muscles, but fat is the most abundant resource that the body uses for energy.  Caffeine enters the body and forces the working muscles to utilize as much fat as possible.  This delays the immediate depletion of glycogen.  Studies show that in the first fifteen minutes of exercise caffeine has the potential to reduce the loss of glycogen by fifty percent.  When this happens, the saved glycogen can be used for the remainder of the workout where normally it would be entirely depleted.  (

          However, a study involving 9 trained athletes set out to provide proof of caffeine’s ability to work as an ergogenic aid before and during the workout.  “In this study involving a 2 hour cycle endurance test, Ivey et al. (1979) found that 250mg of caffeine 1hour before the test and another 250mg total divided in doses every 15 minutes during the test led to higher work output throughout the test” (Dews, p.89)  This study resulted in a 7 percent average increase in total output among the athletes.  By consuming caffeine during high endurance activities, it is possible to increase the total output.

          The second theory deals with the prospect of caffeine enhancing the athlete’s mental focus.  Caffeine has been proven to be a recognized stimulant to the central nervous system.  By slowing substances used to stop neuronal firing, caffeine can quicken reactions and increase mental awareness.  And finally, caffeine may have the ability to strengthen muscle contractions.  By transferring calcium, sodium, and potassium in the cells, membrane permeability increases.  This in turn results in more powerful muscle contractions.  Scientist Gene Spiller has performed many studies in order to confirm this belief.  “In a double blind, placebo controlled experiment where caffeine was isolated, caffeine was found to increase muscular force output at low frequencies of electrical stimulation (10 to 50Hz).  There was no significant change at higher frequencies of electrical stimulation like 100Hz” (Spiller, 1998).  This reflects the belief that caffeine has the ability to create more forceful muscle contractions.   Once again, all three of these theories are subject to many different factors, and the precise process by which caffeine affects the body is unknown. (

Caffeine Controversy

          This being the summer of the 2000 Olympics, it is relevant to know that caffeine is one of the many drugs that will not be permitted during the summer games.  The International Olympic Committee (IOC) presently lists caffeine as a banned substance.  It is difficult to believe that a substance consumed by over 75% of Americans everyday, is placed in a category, which includes harmful drugs such as steroids and cocaine.  Urinary test above 12mg/liter (8 cups of coffee) is perceived by the IOC as a deliberate attempt by an athlete to gain an advantage on the competition.


Side Effects of Caffeine

          Caffeine presents many side effects to regular users and also moderate consumers.  At one point many researchers looked to link caffeine with heart disease and cancer.  Also many studies have shown that blood pressure is increased with the consumption of caffeine, but the results of these studies vary.  For the most part these beliefs have been put to rest due to extensive testing.  Currently there is no evidence that links caffeine to cancer, cardiovascular disease, or high blood pressure.  However, caffeine causes many side effects that can still cause many problems among athletes as well as the regular person.  These side effects include sleep deprivation, nausea, cramping, anxiety, fatigue, headaches, and gastrointestinal instability.  For athletes, caffeine has more disastrous effects that may affect performance.  These side effects include muscle tightness, muscle cramping, and dehydration.  The threat of any of these problems during competition is enough to make any athlete think twice before using caffeine in a major event.



Diuretic Effect

          Caffeine consumption has been proven to cause major changes occurring to the kidneys known as the diuretic effect.  Caffeine increases the blood flow in the kidneys and at the same time inhibits the reabsorption of sodium and water.  Also caffeine has been known to weaken the detrusor muscles in the bladder, which provokes the need to urinate.  This poses many problems to athletes participating in long-term endurance activities.  On one hand this can cause the need to urinate, but combined with other aspects such as dehydration and abdominal cramping, can also prove detrimental to the athlete.  Studies have shown that the diuretic effect should not present any problems to athletes who consume moderate caffeine quantities before exercise.

(  In a study to evaluate the amount of excessive sweating in long distance running, 9 athletes were given 450mg of caffeine either with 30 minutes of exercise or without.  The running resulted in a decrease in the urine flow and also a decrease in the amount of caffeine that was excreted in the urine.  This supports the belief that caffeine should not pose a threat of urinary problems to endurance athletes. (Barnard, 1992)


Tips for athletes using caffeine

          For the most part many doctors do not support the use of caffeine in athletics.  For those athletes who believe that caffeine can enhance their performance, there are a few tips that may prove useful maximizing their full potential.  It is important that the athlete refrains from caffeine use 3-4 days before their competition.  This allows for the tolerance levels of caffeine to decrease, thus making the body susceptible to caffeine when consumed.  Also it is important for athletes to understand their caffeine limits.  If you have never used caffeine for sporting enhancement, then you are unfamiliar with caffeine’s affects on your body.  Make sure that you have used caffeine in a variety of training conditions to understand your limitations.  Also it is advantageous to ingest caffeine 2-3 hours before competition to ensure a peak of performance.  Studies have shown that it takes several hours for caffeine to enter the body and exploit the use of fat, thus storing glycogen for endurance.  All of these tips are essential in making the most of caffeine’s benefits in athletics. (



          In conclusion, caffeine’s use as an ergogenic aid has been proven to increase physical endurance but has many side effects and precautions.  However, caffeine’s use for short-term endurance appears to have no affect on the athlete.  Many sources seem to support these two statements, but it seems that the general consensus is for athletes to avoid the use of caffeine.  The International Olympic Committee treats caffeine as any other illegal drug, which poses a serious question on how advantageous the substance is to athletes?  Caffeine poses many potential side effects that can affect one’s lifestyle.  It is important that the user understands their caffeine limitations before habitual use, especially athletes.  There are many factors that shape caffeine’s effect on the individual.  Factors such as metabolism, consumption, and frequency of use should all be taken into account before the use of caffeine in athletics.  


Dews, Peter B. (1984) Caffeine: Perspectives From Recent Research. New York: Springer Verlag

Nash, Harvey (1962) Alcohol and Caffeine: a study of their psychological effects. New York

Spiller, Gene A. (1998) Caffeine. Boca Raton: CRC Press, 233-250

Tarnopolsky, Mark. (1999) Gender Differences in Metabolism: Practical and nutritional implications;

          Caffeine. Boca Raton: CRC Press, 155-200

Zhang, Yong. (1989) The Effects of Chronic Caffeine Ingestion on Peripheral Adenosine Receptors.

          New York.

Brecher, Edward M. (1972) Licit and Illicit Drugs; The Consumers Union Report on narcotics, stimulants, depressants, inhalants, Hallucinogens, and marijuana- including caffeine, nicotine, and alcohol. New York, 291-390

Graham, TE. (1998) Effects of Caffeine on Metabolism, Exercise Endurance and Catecholamine 

          Responses and Withdrawl. London

Barnard, J. (1992) Caffeine in Sport: influence of endurance exercise on the urinary caffeine




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