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Caffeine in Sport
MECHANISMS OF ACTION
In this report:
Caffeine consumption can affect the body in a number of ways, principally through the Key Points
inhibition (competitive blockade) of Sound evidence exists to demonstrate that adenosine receptors (2). Due to the complex caffeine has ergogenic effects on both short biochemistry and interacting responses, the and long term endurance as well as short term underlying mechanisms behind the high intensity intermittent exercise ergogenic effect of caffeine remain unclear. Evidence also supports the positive effect of One suggested mechanism is through the caffeine on many cognitive aspects of modulation of the hormones involved in fat performance such as concentration, alertness, metabolism which may result in glycogen memory and reaction time sparing (1). Recent findings, however, do not The mechanism(s) underpinning the support the theory and furthermore fat performance benefits of caffeine remain oxidation is not important in some situations unclear, although it is likely that caffeine when caffeine has been shown to be stimulates the central nervous system altering ergogenic, such as in short term, high sympathetic activity, motor recruitment and intensity activity. perception of effort and pain Performance benefits have been shown with It is well established that caffeine can doses ranging from 1-13 mg/kg body mass; stimulate the central nervous system although it would appear that there is no dose altering sympathetic activity, motor response above 3 mg/kg body mass recruitment and perception of effort and It appears that caffeine does not promote pain (3). It may be this later mechanism diuresis when taken before or during exercise which may account for the ability of caffeine and caffeine is NOT on the WADA list of to enhance sporting performance.
prohibited substances CAFFEINE INGESTION ON
PHYSIOLOGICAL PERFORMANCE
Short and Long Term Endurance
Endurance is best described as the ability of
an athlete to sustain a set or chosen Caffeine (1,3,7-trimethylxanthine) is a naturally intensity for as long as possible and can be occurring compound found in the leaves, nuts and measured in two ways: time trial seeds of various plants. Despite being classified (performance test) or exercise to exhaustion as a drug, caffeine is currently legal, socially (capacity test). Caffeine has been shown to acceptable and enjoys widespread use around the be ergogenic during both protocols with world. Caffeine is commonly consumed in various durations ranging between 3-minutes and forms including coffee, tea and soft drinks, 120-minutes (1,4,5,6,7,8). The magnitude of providing approximately 30-100 mg of caffeine per performance benefit has been recorded serve. Within the UK, the mean daily caffeine between 1.0% and 33%, depending on intake is estimated at 4 mg/kg body mass while it study design. Currently, only a few studies is recognised that heavy tea and coffee drinkers report no ergogenic benefits of caffeine (9), consume an estimated 7.5 mg/kg body mass with no studies reporting a negative effect. (default mass; 50 kg). Supporting research for the These results appear to be independent of ergogenic properties of caffeine stretches back individual fitness level, caffeine dose, 100 years, with the first well controlled study habituation and abstinence (5). reportedly published in 1907 (1) . Since then caffeine has become one of the most widely Short Term High Intensity Intermittent
researched ergogenic aids, with reported benefits applicable across a range of different sports. Stuart et al. (10) and Scheiker et al. (11) have

investigated the impact of caffeine on the short 150 and 225 mg caffeine following a 60- term high intensity intermittent sprinting demands minute cycling time trial improved attention, similar to those of team sports. Despite different complex psychomotor speed and research designs, both reported the ingestion of recognition memory compared with placebo. 6 mg/kg body mass caffeine 60-minutes prior to Similar results have also been observed exercise improved the amount of work done within the military, with the beneficial effects (sprints) compared to placebo in both the first of caffeine ingestion on reaction time and and second half by 6-10%. It was concluded that sustained attention, or vigilance, tasks caffeine can improve performance in an intermittent high intensity team sport by delaying the onset of fatigue. Currently, the effect of One of the most consistently reported caffeine on single sprints lasting less than one outcomes of caffeine ingestion during minute remains unclear.
exercise testing, regardless of mode, intensity or duration of exercise is an Caffeine taken in combination with
alteration in participant's perceptual response. In 2004, Doherty and Smith (3) Recent research has suggested that the completed a meta-analysis on the impact of ingestion of caffeine in combination with caffeine on Rating of Perceived Exertion carbohydrate may have synergistic effects on (RPE) and reported that in comparison to performance. In 2000, Van Nieuwenhoven et al. placebo caffeine represents a 6% reduction (12) reported that intestinal glucose absorption in the RPE, independent of subject was increased by 23% when caffeine was withdrawal, caffeine dose and interval time ingested with carbohydrate (1.4 mg/kg and 0.5 between ingestion and exercise. In many g/min respectively). As intestinal absorption is sporting environments, a reduction of one of the limiting factors for exogenous perceived effort at a given exercise intensity carbohydrate oxidation, Yeo et al (13) investigated may result in improved concentration, whether the ingestion of caffeine with reaction times, precision and motor co- carbohydrate would increase the availability of ingested carbohydrate and thus exogenous carbohydrate oxidation during prolonged PRACTICAL CONSIDERATIONS OF
endurance exercise. In 8 well trained cyclists a 26% increase in exogenous carbohydrate oxidation was found. As carbohydrate feeding Well controlled studies demonstrate that the during prolonged exercise can postpone fatigue ingestion of 3-13 mg/kg body mass caffeine and enhance endurance capacity, the potential improves endurance performance (i.e. 210 application to the endurance performer is – 910 mg caffeine for a 70 kg athlete). Of those studies investigating varying doses of caffeine it would appear that a caffeine CAFFEINE INGESTION ON COGNITIVE
intake of 3 mg/kg body mass improves performance, but higher intakes will not There is a long history of scientific interest into always result in an increased benefit (6,8,17). the effects of caffeine on cognitive functions. Interestingly, the work of Cox et al., (4) Research has clearly demonstrated that caffeine reported improvements in performance with through its effects on the central nervous system, caffeine ingestion at doses as low 1 mg/kg can significantly improve alertness (14), body mass in cyclists with no dose concentration (15,16), memory (7,14) and reaction response following a time trial performance. time (14,16). Such results have been shown to Currently data investigating the comparison occur at caffeine doses as low as 12.5 mg to of single and repeated doses of caffeine has doses as high as 350 mg, with the ingestion of found that caffeine divided between before caffeine in isolation (16) or in combination with and during exercise provides no ergogenic carbohydrate (7,15). Whilst further sport and effect on endurance performance over a exercise specific research is required in this area, bolus dose before exercise (18). Hogervorst et al. (7) did report the ingestion of

As it is commonly reported that the maximum Graham, T.E. (2001). Caffeine and Exercise: concentration of caffeine in the body is typically Metabolism, Endurance and Performance. Sports attained within one hour (1), it is general practice Medicine, 31, 785-807.
for athletes to consume caffeine 60-minutes prior Sinclair, C.J.D. and Geiger, J.D. (2000). Caffeine use in sports: A pharmacological review. Journal of to exercise.
Sports Medicine and Physical Fitness, 40, 71-79.
Doherty, M. and Smith, P.M. (2005). Effects of Diuretic effect of caffeine
caffeine ingestion on rating of perceived exertion Caffeine under sedentary conditions may have a during and after exercise: a meta-analysis. Scandinavian Journal of Medicine and Science in diuretic action (19), and athletes are often advised Sports, 15, 69-78.
to avoid beverages containing caffeine in Cox, G.R., Desbow, B., Montgomery, P.G., situations where fluid balance may be Anderson, M.E., Bruce, C.R., MacRides, T.A., compromised. Studies specific to exercise that Martin, D.T., Moquin, A., Roberts, A., Hawley, J.A. and Burke, L.M. (2002). Effect of different protocols have quantified body weight loss, sweat rates, of caffeine intake on metabolism and endurance plasma volume electrolytes and core temperature performance. Journal of Applied Physiology, 93,
did not find any impact of caffeine ingestion (6,20). Thus, caffeine is a diuretic in resting conditions Doherty, M. and Smith, P.M. (2004). Effects of caffeine ingestion on exercise testing: A Meta- but not during exercise and therefore it would analysis. International Journal of Sport Nutrition and appear there is no clear reason to refrain from Exercise Metabolism, 14, 626-646.
caffeine containing drinks in such situations Graham, T.E. and Spriet, L.L. (1995). Metabolic, catecholamine and exercise performance
responses to various doses of caffeine. Journal of
Applied Physiology, 78, 867-874.
Hogervorst, E., Riedel, W.J., Kovacs, E. and Jolles, Caffeine is mainly excreted from the body in the J. (1999). Caffeine improves cognitive performance urine; the time to clear half of ingested caffeine is after strenuous physical exercise. International
Journal of Sports Medicine, 20, 354-361.
3-5 hours. This however, is subject to Kovacs, E.M.R., Stegen, J.H.C.H. and Brouns, F. considerable individual variation with several (1998). Effect of caffeinated drinks on substrate factors including genetics, prior ingestion of metabolism, caffeine excretion and performance. caffeine, gender, exercise, diet and use of certain Journal of Applied Physiology, 85, 709-715.
Butts, N.K. and Crowell, D. (1985). Effect of drugs shown to affect the metabolism and thus caffeine ingestion on cardiorespiratory endurance in half life of caffeine (2). It is for this reason that the men and women. Research Quarterly in Exercise World Anti-Doping Agency (WADA) have and Sport, 85, 301-305.
struggled to find a consolidated position on Stuart, G.R., Hopkins, W.G., Cook, C. and Cairns, S.P. (2005). Multiple effects of caffeine on caffeine and why caffeine currently remains off simulated high intensity team sport performance. the list of prohibited substances. Medicine and Science in Sports and Exercise, 37,
1998-2005.
Possible Adverse Effects
Schneiker, K.T., Bishop, D., Dawson, B. and Hackett, L.P. (2006). Effects of caffeine on Caffeine use in sport can have side effects, prolonged intermittent sprint ability in team sport particularly when ingesting high doses (greater athletes. Medicine and Science in Sports and than 500 mg per day) or when taken by those Exercise, 38, 578-585.
individuals not consuming caffeine on a regular Van Nieuwenhoven, M.A., Brummer, R-J.M. and basis. Side effects may include gastrointestinal Brouns, F. (2000). Gastrointestinal function during exercise: comparison of water, sports drink and distress, headaches, tachycardia, restlessness, sports drink with caffeine. Journal of Applied irritability, tremor, elevated blood pressure, Physiology, 89, 1079-1085.
psychomotor agitations, and premature left Yeo, S.E., Jentjens, R.L.P.G, Wallis, G.A. and ventricular contractions. Whilst these symptoms Jeukendrup, A.E. (2005). Caffeine increases exogenous carbohydrate oxidation during exercise. are caused by the effect of caffeine on the CNS, Journal of Applied Physiology, 99, 844-850.
they are individual in nature and therefore Smith, A., Sturgess, W. and Gallagher, J. (1999). caffeine ingestion should be trialled in training Effects of low dose caffeine given in different drinks prior to use in competition. If side effects occur on mood and performance. Human
Psychopharmacology and Clinical Experiments, 14,
an athlete should consult their physician. Gillingham, R.L., Keefe, A.A. and Tikuisis, P.
(2004). Acute caffeine intake before and after
fatiguing exercise improves target shooting
engagement time. Aviation Space Environment
Medicine, 75, 865-871.

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