Caffeine and Endurance

Caffeine continues to be one of the most studied ergogenic ingredients. Researchers are constantly re-designing studies to get a clear indication how caffeine improves performance. In 2004-2005 over a dozen studies have been published on the effects of caffeine as an ergogenic aid. This newsletter reviews five of those studies.

For years athletes have been using caffeine in various doses to improve their performance. Everyone knows that a strong cup of Java gives you that alertness and sense of extra energy. Drink three cups of leaded Starbucks coffee and you’ll feel like you want to run a marathon! So….does the caffeine just make you want to run that marathon or do you actually run it and run it faster? Many professional endurance athletes use caffeine to enhance their performance. Prior to 2004, Caffeine was banned by the US Olympic Committee, World Anti-Doping Association (WADA) and US Anti-doping association.

This decision was reversed in 2004, allowing the use of caffeine in sports, though this reversal may be short lived. Research published in 2004 and 2005 continues to indicate that caffeine does elicit an ergogenic boost. Prior to 2004, Caffeine was banned at a level of 12mcg/ml in urine, which requires about 1,200 mg of pure caffeine or 8 cups of strong coffee. WADA has lifted this ban starting in January of 2004, although it comes with some controversy since caffeine does have some ergogenic properties and can be dangerous if abused. Back to that marathon: you can run it faster, but only if done correctly, so let’s talk about who can benefit from caffeine and how it can be properly used.

Caffeine stimulates the central nervous system (CNS), increases the release of adrenaline, increases the use of body fat as fuel and spares glycogen. Adrenaline release is accomplished through caffeine’s effect on epinephrine and nor-epinephrine. This CNS excitatory response is used by many athletes to give them that alertness and sense of extra ‘energy’ needed for their workouts. More importantly, caffeine mobilizes free fatty acids (FFA) in the blood. Increased FFA in the blood allows the body to use fat as a fuel source. The use of fat as fuel allows the body to spare glycogen (carbohydrates) for later use in exercise.

Notes to consider:

*Caffeine is classified as a diuretic.* This can complicate an athlete’s water balance, which determines how efficient he/she will perform. Diuretics not only dehydrate the body, they can cause bowel movements and gastric distress which would obviously be detrimental to your exercise bout.

*Recently some experts and publications have reversed their viewpoint of caffeine’s diuretic properties. The current literature is contradictory in respect to caffeine’s classification as a diuretic.—see Diuretic effects of caffeine below

*Habitual caffeine users will not see any ergogenic effects from caffeine prior to a race. Your body has an intricate natural defense mechanism (builds a tolerance) which over time compensates for high doses of most nutrients and chemicals you put in your body. In other words, if you habitually use caffeine you can expect your body to reduce all the beneficial endurance and performance effects. *So recent publications have also shown this may not necessarily be true.

*Caffeine is also a thermogenic. This means it will raise your heartbeat and core body temperature. As you can guess, this may not be wise when exercising in heat.

*Caffeine has not shown any benefit on power.

The previous four points may lead you to believe that caffeine should not be used by anyone as an ergogenic aid. In fact, the majority of the research on sedentary individuals does not support the use of caffeine as an ergogenic aid. However, the research done on trained athletes showed no detrimental diuretic effect and no increased body temperature. Caffeine has been shown to increase power, reduce the perceived effort at a given workload, e.g., cycling at 24mph may seem easier when loading with caffeine.

Diuretic Effects of Caffeine

Depending on several factors, the diuretic effects caused by caffeine can be considered weak to negligible under normal caffeine consumption and for people without urinary tract problems. However, it is difficult to measure the effects, even in a laboratory situation.

A study by Nussberger et al. (1) does not show a significant increase of urine excretion when comparing intake of drinks containing caffeine to the water control intake. Transitory effects have been reported by Neuhäuser-Berthold et al. (2) when passing from abstinence to an elevated dose or when a chronic intake is followed by massive absorption. Such transitory imbalances disappear after less than an hour. A study by Martof and Knox (3) concluded that there is no evidence to recommend that xanthines should be omitted when forcing fluids. Even in a recent epidemiological study attempting to classify alcohol and caffeine as diuretic substances (4) , the author admits that there are no estimates of the chronic effect of caffeine on diuresis under variable free-living conditions. Caffeine also causes smooth muscle relaxation particularly in relation to the function of lungs and the blood vessels. Its effect on the detrusor muscle, which is involved in bladder function, has been studied. A control study (5) showed that consumption of caffeine led to a rise in pressure on the detrusor muscle upon bladder filling but not to a diuretic effect as such. Women with normal bladder function were not significantly affected by caffeine. A more recent study (6) confirmed an association between high caffeine intake and detrusor instability in a population of women with symptoms of urinary incontinence.

The beneficial effects of caffeine on endurance exercise performance were discussed in an earlier section. However, there has been concern that use of caffeine during exercise might exacerbate dehydration induced by exercise. Consequently, it has usually been accepted that beverages containing caffeine should not be used to promote fluid replacement during prolonged exercise. Wemple and collaborators (7) , however, demonstrated that the presence of caffeine in drinks, taken before moderate endurance exercise, did not compromise hydration of the body, even though it did cause weak diuresis during rest. In a study aimed at assessing the effects of caffeine on endurance Graham and collaborators (8) did not observe differences among their trials in the volume of urine produced during preexercise and postexercise when comparing different fluids, decaffeinated coffee, placebo capsules, decaffeinated coffee with caffeine added, regular coffee and caffeine capsules.

1.Nussberger, J. et al. Journal of cardiovascular Pharmacology, 15, 685-691, 1990.
2.Neuhäuser-Berthold, M. et al. Annals of Nutrition & Metabolism, 41, 29-36, 1997.
3.Martof, M.T. and Knox, D.K., Clinical Nursing Research, 6, 186-196, 1997.
4.Stookey, J.D., European Journal of Epidemiology, 15, 181-188, 1999
5.Creighton, S.M. and Stanton, S.L. British Journal of Urology, 66, 613-614, 1990.
6.Arya, L.A. et al. Obstetrics & Gynecology, 96, 85-89, 2000.
7.Wemple, R.D. et al. International Journal of Sports Medicine, 18, 40-46, 1997.
8.Graham, T.E. et al. Journal of Applied Physiology, 85, 883-889, 1998.

The above excerpt was borrowed from The Coffee Science Information Center.

About the author


Robert Kunz - First Endurance