Caffeine in Sport
MECHANISMS OF ACTION
In this report:
Caffeine consumption can affect the body in a number of ways, principally through the
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
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.
CAFFEINE INGESTION ON
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
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,
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.
Lieberman, H.R., Wurtman, R.J., Emde, G.G.,
Roberts, C. and Covielle, I.L. (1987). The effects of
low doses of caffeine on human performance and
mood. PsychoPharmacology, 92, 308-312.
Pasman, W.J., van Baak, M.A., Jeukendrup, A.E.
and de Haan, A. (1995). The effect of different
dosages of caffeine on endurance performance time.
International Journal of Sports Medicine, 16, 225-
Conway, K.J., Orr, R. and Stannard, S.R. (2003).
Effect of a divided caffeine dose on endurance
cycling performance, post exercise urinary caffeine
concentration and plasma paraxanthine. Journal of
Applied Physiology, 94, 1557-1562.
Maughan, R.J. and Griffin, J. (2004). Caffeine
ingestion and fluid balance: a review. Journal of
Human Nutrition and Dietetics, 16, 411-420.
Wemple, R.D., Lamb, D.R. and McKeever, K.H.
(1997). Caffeine vs. caffeine free sports drinks:
effects on urine production at rest and during
prolonged exercise. International Journal of sports
Medicine, 18, 40-46.
Armstrong, L.E. (2002). Caffeine, body fluid-
electrolyte balance, and exercise performance.
International Journal of Sport Nutrition and Exercise
Metabolism, 12, 189-206
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