in Fitness and Exercise
Does caffeine have beneficial effects on exercise, and if so what
are they? Will it have any detrimental effects on performance? What
sports would it be beneficial in?
Caffeine is the most highly consumed stimulant throughout the world,
with over 500 million cups of coffee consumed everyday. It is found
naturally in coffee beans, tea leaves and cocoa, and is contained
in numerous soft drinks, confectionary items, tea and coffee.
Caffeine is a behaviourally active substance that belongs to a
group of lipid-soluble purines, the chemical name being 1,3,7-trimethylxanthine.
It is absorbed rapidly from the intestinal tract with the peak plasma
concentration being reached within an hour. The blood caffeine concentrations
have a half life of about 3-6 hours meaning that it clears from
the body relatively quickly. It is the aim of this investigation
to determine the particular effect caffeine has on specific aspects
of sports performance.
The optimum dosage an athlete should take will depend on their
reasoning for taking the drug, however there is evidence to show
that there is no relationship between the dosage consumed and the
In a study by Pasman WJ et al. it was found that endurance performance,
specifically time to fatigue, was increased in all the athletes
that were administered caffeine when compared to the placebo. However
it was also found that there was no dose-response relationship.
The subjects were administered 5,9 or 13 mg of caffeine per kilogram
body mass 1 hour before cycling at 80% of maximal power in a VO2
max test. All trials showed a 24% improvement when compared with
the non-caffeine consuming placebos. More notably there was no additional
benefit when caffeine quantities were consumed above 5 mg per kilogram
Benefits of Caffeine in Training
Caffeine can have benefits for strength training. It was found
in a study by T.A.Astorino et al that although caffeine did not
noticeably improve their subjects 1 repetition maximum (1RM) (leg
press and barbell bench press), when training at 60% improvements
were noticed. Although when working at 60% of the 1RM the weight
lifted did not change, muscular endurance was shown to increase
by 11-12% with the use of caffeine when compared to placebo. Although
this does not directly show that caffeine does not increase the
1 repetition maximum, it does show that the subject can train for
longer, and this will indirectly be beneficial in progressing the
1RM because it means the muscles will have to become used to more
work, therefore grow to meet the demands placed on them. From this
we can see that ingesting caffeine can benefit strength training
for sports that require larger muscle masses such as Rugby (union
and league), Lacrosse or American Football. Consuming a highly caffeinated
energy drinks prior to gym training should increase the benefits
gained from strength training.
Caffeine has also been shown to have positive effects on endurance
sports. It was found in a study by Costill et al. that ingesting
caffeine stimulated Free Fatty Acid (FFA) mobilisation, retarded
depletion of muscle glycogen, and therefore enhanced endurance exercise
performance. Prior to this, research on animals and humans suggested
that elevating plasma FFA spared muscle glycogen and therefore extended
exercise capacity. It has been found that the FFA concentration
rises after an injection of heparin (this substance stimulated FFA
mobilisation and subsequent oxidation). Like Heparin, caffeine also
mobilises Free Fatty Acids. Costill investigated caffeine's effect
on muscle glycogen levels, the metabolic mixture in exercise, and
the endurance performance in athletes. In this study, Costill chose
9 trained, male and female athletes, exercising on a cycle ergometer
at 80% of their maximal oxygen uptake (VO2max) until exhaustion.
Blood samples where taken before and during the experiment to determine
Plasma lactate, FFA and glucose. It was found that the subjects
where able to exercise 20% longer, having 1 hour prior to the test
consumed 330mg caffeine, when compared to an original test, taken
3 days earlier, where a placebo was used. Free Fatty Acids where
found not to differ significantly between conditions, but the caffeinated
drink used was seen to significantly increase plasma glycerol levels.
With caffeine, fat oxidation is significantly higher for the duration
of the experiment, with 118g oxidised compared to 57g without caffeine.
Costill’s study demonstrated that the ingestion of caffeine
before exercise increased the rate of lipolysis during sustained
exercise. This is significant because an increased rate of lipolysis
could spare liver and muscle glycogen in the early stages of endurance
exercise for later use. These benefits would be ideal for marathon
runners where they are exercising between 2-3 hours. Having glycogen
stores used later would be very beneficial. It is also important
to note that having ingested caffeine, the subjects perceived the
exercise to be easier, possibly demonstrating a psychological effect.
Psychological Effects of Caffeine
The Psychological effects of caffeine must also be noted. Sökmen
and Bülent-Armstrong have shown that there is no difference
in exercise performance when taking lower doses as opposed to higher
doses. In fact there are benefits in taking caffeine at lower doses
before intense training. It was found that it can be taken gradually
at low doses to avoid tolerance over a 3-4 day period prior to intense
training as this helps to sustain exercise intensity without affecting
sensitivity to the drug, which may increase the subjects tolerance.
It also improves cognitive aspects of performance, such as concentration,
if an athlete has not slept well the night before, helping the athlete
to focus more on their performance.
The ability of caffeine to improve concentration was also found
in a military study by Gillingham et al, examining the effect of
caffeine on target detection and rifle marksmanship during simulated
combat operations. Caffeine ingestion was seen to improve engagement
speeds during vigilance exercises after 2.5 hour loaded run and
then 2.5 hour shooting exercises. This shows evidence that caffeine
can help to maintain alertness in stressful situations, like that
which an athlete may face such as the biathlon (cross-country skiing
and shooting). The evidence shows caffeine ingestion improves the
speed of target recognition after strenuous exercise, and this is
very beneficial for biathletes or those in similar sports as it
can improve performance.
Drawbacks of Taking Caffeine when Training
Other studies suggest, however, that caffeine may also have a negative
effect on training. Graham T.E et al. tested the suggested adverse
effect that caffeine-induced diuresis leads to fluid and electrolyte
loss and a decrease in plasma volume. In a comparative study between
caffeine and coffee intake, the subjects urine was tested an hour
after intake and after exercise. Graham et al found no difference
in urine output between either caffeine or coffee. Quantitative
measurements of body mass loss, sweat rates, plasma volume and electrolytes
did not find and significant change. The reason for this is that
while caffeine is a mild diuretic it takes several hours for changes
in rennin to occur. The presumable reason for this is that exercise
takes place within a shorter period than the time required for caffeine
to noticeably act as a diuretic, and overrides the potential for
fluid loss. This demonstrates that the concern over athletes becoming
dehydrated after consuming caffeine is unfounded. Wemple et al.
gave evidence that caffeine intake results in mild diureses, however
if exercise had taken place there was no diuretic effect. It is
also to note in either case, the diureses did not provide measurable
effects on plasma volume, rate of sweat perfusion or urine osmolarity.
There is evidence of a physical dependence on caffeine. Strain
et al. discovered substance dependency in caffeine, where dependence
is characterised by tolerance, withdrawl symptoms, taking the substance
in larger doses and persistent desires for caffeine. Withdrawl symptoms
include headaches, mood changes, drowsiness and fatigue. Dependency
can develop within 3 days of regular consumption. Symptoms develop
between 12-24 hours, peaking 24-48 hours and lasting around 7 days.
The dependency is generally mild with some subjects not presenting
a dependency. Strain et al. found that the syndrome is similar to
substance dependency syndromes for other psychoactive drugs. A few
individuals also presented with caffeine-induced anxiety attacks.
Although evidence for caffeine dependency exists, the effects are
generally very mild. An athlete’s performance should not demonstrate
any noticeable adverse affect.
In conclusion, it has been shown that caffeine does have a definite
effect on exercise performance, although it benefits different exercises,
sports and types of training in different ways. We can see the most
noticeable effect gained in endurance training. The least effect
would be during one repetition maximum tests although it does provide
benefits in strength training.
The negative effects, both psychological and physiological although
present are minimal when compared to the potential gains. Caffeine,
when taken in lower doses should benefit athletic performance in
Exercise Physiology. Energy, Nutrition and Human Performance (Sixth
McArdle, Katch & Katch
Published by Lippincott Williams & Wilkins
Costill DL, et al.
Effects of caffeine ingestion on metabolism and exercise performance.
Medicine, Science and Sports Exercise 1978;10:155
Caffeine and Exercise; Metabolism, Endurance Performance
Terry E. Graham
Sports Med 2001; 31(11):785-807
Effects of caffeine ingestion on one-repetition maximum muscular
Todd A. Astorino, Riana L. Rohmann and Kelli Firth,
Eur J Applied Physiology (2008) 102:127-132
Caffeine Use in Sports: Considerations for the Athlete
Sökmen, Bülent – Armstrong