CAFFEINE AND EXERCISE PERFORMANCE
Terry E. Graham, Ph.D.
Lawrence L. Spriet, Ph.D.
Department of Human Biology & Nutritional Sciences
Member, GSSI Sports Medicine Review Board
Department of Human Biology & Nutritional Sciences
1. Recent, well-controlled studies have established that moderate doses of caffeine ingested 1 h prior to exercise enhance the performance of
certain types of endurance exercise in the laboratory. Moderate caffeine doses produce urinary caffeine levels well below the allowable limit,as determined by the International Olympic Committee. The results are specific to well-trained elite or recreational athletes. It is not knownif these findings will improve performance in competitions because controlled field studies of the effects of caffeine are lacking.
2. The mechanisms responsible for improved exercise endurance in prolonged exercise remain elusive. A metabolic mechanism appears to con-
tribute early in exercise, when caffeine ingestion increases plasma free-fatty acid concentrations and muscle triglyceride use and sparesmuscle glycogen. However, it is not clear if increased fat oxidation causes the glycogen sparing in muscle. Increases in plasma epinephrineconcentrations usually occur following caffeine ingestion but are not essential for the accompanying metabolic changes. When studying caf-feine effects in the human it is difficult to identify the primary source of the "stimulus" because caffeine usually increases epinephrine secre-tion and is also rapidly metabolized in the liver to three dimethylxanthines (paraxanthine, theophylline and theobromine). Thedimethylxanthines can remain in the circulation longer than caffeine and may be metabolic signals in their own right.
3. Caffeine appears to enhance performance during short-term, intense cycling lasting ~5 min in the laboratory and in simulated 1500 m race
time. However, positive ergogenic effects of caffeine are much less frequent during sprint exercise lasting less than 90 s and in incrementalexercise tests lasting 8-20 min.
4. Potential mechanisms for improving performance during intense exercise lasting 5-20 min include direct effects of caffeine on the central
nervous system and/or excitation-contraction coupling and increased anaerobic energy provision in skeletal muscle.
Caffeine is a "controlled or restricted drug" in the athletic world, because urinary levels of greater than 12 µg/mL following competitions are
considered illegal by the International Olympic Committee (IOC). However, most athletes that consume caffeine beverages prior to exercisewould never approach the illegal limit following a competition. Therefore, caffeine occupies a unique position in the sports world. It is aninherent part of the diet of many athletes although it has no nutritional value and also has the potential to be a "legal" ergogenic aid in manyexercise situations. While it is common to equate caffeine with coffee, it should be noted that rarely is coffee the vehicle of administration inresearch studies. Therefore, it may be misleading to equate the two because coffee contains hundreds of additional chemicals.
In a 1990 Sport Science Exchange article, Wilcox concluded that few well-controlled studies had examined the effects of caffeine on
endurance performance and that the results were inconsistent. Since 1990, the research examining caffeine and exercise performance increasedand demonstrated the ergogenic effect of caffeine during prolonged endurance exercise (Graham & Spriet, 1991, 1995; Pasman et al., 1995). Inaddition, investigations examining the effects of caffeine on exercise performance during sprinting (<90 s), intense exercise of short (~5 min)and long duration (~20 min)(Collomp et al., 1990, 1991; Jackman et al., 1996; MacIntosh & Wright, 1995) have appeared.
There has been general improvement in the quality of the investigations because researchers have attempted to control several factors that
may confound the caffeine results. Conlee summarized these factors in a 1991 review article. Three factors relate to the nature of the experi-mental design, i.e., the exercise modality, the power output, and the caffeine dose, whereas four others relate to the status of the subjects prior tothe experiment, i.e., nutritional status, training status, previous caffeine use, and individual variability. An additional factor is the ability to reli-ably measure exercise performance. This reliability is greater in highly trained subjects than it is in the less well-trained.
Caffeine appears to be taken up by of all tissues of the body, making it difficult to independently study the effects of caffeine on the central
nervous system, the muscles, and fat tissue in the exercising human. It is also apparent that different mechanisms are probably responsible forperformance enhancement in different types of exercise. However, it is important to note that the mechanism(s) may not be entirely due to caf-feine. For example, caffeine ingestion usually increases the plasma concentration of epinephrine, a hormone with widespread effects, and the
liver rapidly metabolizes the caffeine, a
trimethylxanthine, into three dimethylxan-
(VO2max) (Costill et al., 1978). The trained
thines, i.e., paraxanthine, theophylline, and
cyclists improved performance from 75 min
were rare with doses at or below 6 mg/kg,
but prevalent at higher doses (9-13 mg/kg).
metabolites increase in the plasma as the
lowing caffeine ingestion. A second study
caffeine concentration declines, and parax-
decreased performance in some athletes at
potential metabolic stimuli. Thus, it is diffi-
amount of work performed in 2 h (Ivy et al.,
cult to resolve which tissues are directly or
1979). These studies suggested that utiliza-
increase in venous plasma EPI at rest and
indirectly affected by which compound.
tion of fat for energy increased by ~30% in
the caffeine trials. A third study examined
at rest. The elevated FFA with caffeine was
"caffeine" is used in this report, the reader
that ingestion of 5 mg of caffeine/kg body
mg/kg), performance was increased without
significant increases in plasma venous EPI
al., 1980). In the 1980's, few investigations
THEORIES OF ERGOGENICITY
actually tested the ergogenic effects of caf-
reduced following caffeine ingestion, but
the "sparing" was limited to the initial 15
ergogenic effect of caffeine during exercise.
The first theory suggests a direct effect on
affected by caffeine. Furthermore, conclu-
some portion of the central nervous system
sions regarding the metabolic effects of caf-
There is little information on the perfor-
that affects the perception of effort and/or
feine were often based on indirect indicators
mance and metabolic effects of caffeine in
the neural activation of muscle contraction.
of fat metabolism, i.e., increases in plasma
recreationally active or untrained subjects
The second theory proposes a direct effect
free-fatty acids (FFA) and/or decreases in
because performance in these groups is dif-
of caffeine on skeletal muscle performance.
the ratio of carbon dioxide production to
ficult to measure accurately. Chesley et al
This may involve ion transport (including
(1994) reported a variable glycogen sparing
Ca2+ transport) and direct effects on key reg-
response to a high caffeine dose (9 mg/kg)
ulatory enzymes, including those control-
these suggestions is largely derived from in
1995; Tarnopolsky, 1994, Wilcox, 1990).
investigations in which high pharma-
results suggest that the metabolic responses
to caffeine ingestion in untrained subjects
used to demonstrate effects. If these "test-
RECENT STUDIES OF CAFFEINE
are more variable than in aerobically trained
tube" results have any relevance during
EFFECTS ON ENDURANCE
exercise, the most likely candidates for con-
PERFORMANCE AND METABOLISM
tributing to an ergogenic effect of caffeine
are changes in calcium activity and in the
effects of caffeine (4.5 mg/kg) in "pure"
effects of caffeine in well-trained athletes
tablet form to the same amount of caffeine
from the extracellular fluid to the interior of
who are accustomed to exhaustive exercise
in a coffee beverage (~two mugs of strong
the muscle fibers; caffeine levels during
and race conditions. Most confounding fac-
coffee ingested in 10 min). Caffeine as a
exercise are similar to the lowest concentra-
tors were well controlled, and performance
tablet resulted in the usual metabolic and
tions of caffeine used in vitro
that can affect
performance effects, but when ingested as
petitive conditions. The studies examined
a beverage there was less of a response in
The third theory is the classic or "meta-
the effects of a caffeine dose of 9 mg/kg
plasma epinephrine and little or no effect
bolic" explanation that involves an increase
in fat oxidation and a reduction in carbohy-
exhaustion at 80-85% VO2max (Graham &
caffeine concentrations were identical.
drate oxidation. In this scheme, caffeine
Spriet, 1991: Spriet et al., 1992), the effects
directly enhances the activity of enzymes
of varying doses (3-13 mg/kg) of caffeine
that break down fat into fatty acids or caf-
on cycling performance (Graham & Spriet,
feine increases circulating levels of epi-
1995; Pasman et al., 1995) and the effects
stores in fat or muscle tissue. The increased
cycling (5 min rest between bouts) at 85-
fatty acid availability increases muscle fat
90% VO2max (Trice & Haymes, 1995).
oxidation and reduces carbohydrate oxida-
tion, thereby improving the performance of
important findings. Endurance performance
exercise that becomes exhausting when car-
except at the low caffeine doses for which
placebo trial ~20-50% following ingestion
this hypothesis has not been fully examined.
The increased FFA at the onset of exercise,
of varying doses of caffeine (3-13 mg/kg) in
the glycogen sparing in the initial 15 min,
elite and recreationally trained athletes who
and the report of increased intramuscular
varying types of exercise that are catego-
TG use during the first 30 min of exercise
rized according to power output and time to
exception, the 3, 5, and 6 mg/kg doses pro-
suggest a greater role for fat metabolism
exhaustion or to completion of a race.
duced an ergogenic effect with urinary caf-feine levels that were below the IOC
early in exercise following caffeine doses of
acceptable limit. Three of four experiments
CAFFEINE AND ENDURANCE
using a 9 mg/kg dose reported performance
bolic findings do not preclude other factors
increases, while 6/22 athletes tested in these
contributing to enhanced endurance perfor-mance. For example, caffeine appears to
studies had urinary caffeine levels at or
stimulate transport of potassium into inac-
ergogenic aid was initially stimulated by
tive tissues, leading to an attenuation of the
work from Costill's laboratory. They exam-
ined the effect of ingesting 330 mg of caf-
athletes had urinary caffeine levels well
during exercise. It has been postulated that
feine 1 h prior to cycling to exhaustion at
above 12 µg/mL. The side effects of caf-
the lower plasma potassium helps maintain
CAFFEINE AND PERFORMANCE OF
the excitability of the cell membranes in
SHORT-TERM INTENSE EXERCISE
events lasting less than 90 s. The amount
contracting muscles and contributes to caf-
feine's ergogenic effect during endurance
effects of caffeine on performance during
processes would be ~75-80% of the total in
the first 30 s, ~65-70% over 60 s, and ~55-
lasting ~5 min; near-maximal provision of
Williams et al. (1988) reported that caf-
changes occurring with caffeine ingestion.
sources is required for such activities.
power output or muscular endurance during
short, maximal bouts of cycling. Collomp et
al. (1992) found that ingestion of caffeine at
exercise. In addition, an infusion of EPI
with placebo to 5:49, although the increase
that was designed to produce exercise EPI
was not significant. A third trial, in which
power or total work completed in six sub-
concentrations similar to those induced by
subjects received 250 mg caffeine daily for
jects performing a 30-s Wingate test.
5 d also increased exhaustion time non-sig-
However, the same group later reported that
250 mg of caffeine produced a significant
(Chesley et al., 1995). Also, Van Soeren et
time on a treadmill in well-trained runners
by 4.2 s compared to placebo (4:46.0 vs.
Therefore, the known alterations in muscle
4:50.2). In a second protocol subjects drank
1992)). The same authors also examined the
metabolism alone cannot presently explain
either coffee or a placebo, ran for 1100 m at
effects of 250 mg of caffeine on two 100-m
freestyle swims that were separated by 20
as fast as possible. The average speed of the
min (Collomp et al., 1990). In well-trained
swimmers, the velocity during the first and
CAFFEINE AND PERFORMANCE
OF GRADED EXERCISE TESTS
Therefore, given the present information,
examined the effects of caffeine ingestion
it is not possible to conclude whether or not
caffeine has an ergogenic effect on sprint
graded exercise protocols lasting 8-20 min
bolic responses to repeated bouts of cycling
performance. The brief and intense nature
of sprint exercise makes it very difficult to
studies from the same laboratory reported
study and to demonstrate significant effects
intervening rest periods of 6 min each. The
of caffeine were given (Flinn et al., 1990;
first two cycling bouts at a controlled power
McNaughton, 1987). The first study used 10
output lasted 2 min, and the third continued
and 15 mg/kg caffeine doses and reported a
to exhaustion. Cycle time to exhaustion was
small, significant increase in performance.
improved with caffeine (4.93 + 0.60 min vs.
However, the control trial always preceded
the caffeine trials, leading to the possibility
as the time taken to reach exhaustion at a
blood lactate measurements throughout the
of an order effect. The second study used a
given power output. However, in the field,
protocol suggested a higher production of
10 mg/kg caffeine dose 3 h prior to cycling
performance is measured as the time taken
lactate in the caffeine trial, even in the ini-
exercise and reported an increased time to
tial two bouts when power output was con-
exhaustion. The subjects completed control,
Consequently, extrapolations from the labo-
trolled. The net rate of glycogen breakdown
placebo and caffeine trials with the control
ratory to field settings may not be valid.
trial always first, and the remaining two
Occasionally, laboratory studies simulate
trials randomized. It appears that the high
race conditions by allowing the subject to
caffeine dose is the most likely factor that
control speed on a treadmill or cadence and
during the protocol. The authors concluded
separates these positive findings from the
resistance on a cycle ergometer in order to
that the ergogenic effect of caffeine during
studies reporting no effect. Unfortunately,
short-term intense exercise was not associ-
no mechanistic information presently exists
work in the shortest possible time. Other
muscle or by altered function of the central
actual race conditions but in time trials.
CAFFEINE AND PERFORMANCE OF
However, these studies still do not entirely
INTENSE AEROBIC EXERCISE
require athletes to exercise at power outputs
conditions, it is often impossible to employ
the controls required to generate conclusive
energy provision, direct effects of caffeine
on the transport of ions in muscles, and cen-
effect of 6 mg caffeine/kg on performance
tral nervous system effects on the sensation
in 1500 m swim trials in trained distance
of effort and/or activation of muscle con-
ingestion on performance during endurance
exercise. Cross-country ski performance in
(min:sec). The authors reported lower pre-
a race lasting 1-1.5 h was improved by 1-
exercise plasma potassium levels and higher
CAFFEINE AND SPRINT
2.5 min compared to a control condition.
post-exercise blood glucose concentrations
Oddly, this improvement occurred during a
with caffeine and suggested that electrolyte
race at high altitude but not at sea level.
fatiguing exercise at power outputs 1.5- to
Unfortunately, the weather and snow condi-
related to the ergogenic effects of caffeine.
3-fold greater than that required to elicit
requiring mathematical "normalization" of
ingest small and large amounts of caffeine,
al., 1990; Gordon et al., 1982). A recent
tions about the validity of the results and
glycogen sparing following caffeine inges-
indicate how difficult it is to perform well-
tion is greater in samples of untrained males
controlled and meaningful field trials.
than in trained males (Chesley et al., 1994;
There is a tremendous need for more field
Spriet et al., 1992). Few females have been
studied to determine if the variability in
response to caffeine ingestion is similar to
that in males. Menstrual status needs to be
been reported with doses of 3-6 mg/kg, it is
easy for endurance athletes to enhance per-
PRACTICAL CONSIDERATIONS OF
estrogen may affect the half-life of caffeine.
formance "legally" with caffeine. We sug-
Therefore, although mean results in a group
gested on the basis of our work that caffeine
of athletes may predict an improved athletic
should be banned prior to competitions inendurance athletes. This would ensure that
Caffeine is a "controlled or restricted
performance, it is impossible to reliably
no athlete had an unfair advantage on race
substance" with respect to the IOC. Athletes
predict that the performance of a given indi-
day but would not prevent caffeine use in
are allowed up to 12 µg caffeine/mL urine
before it is considered illegal. This permits
Habitual Caffeine Consumption
from caffeine ~48-72 h prior to competition
athletes who normally consume caffeine in
to achieve this goal. However, in the pre-
their diets to continue this practice prior to
several recent studies suggest that chronic
competition. An athlete can consume a very
large amount of caffeine before reaching the
exercise and to caffeine but does not affect
amounts to make sure they are not missing
"illegal limit". A 70 kg person could drink
indirect markers of fat metabolism during
about three or four mugs or six regular size
exercise (Bangsbo et al., 1992; Van Soeren
cups of drip-percolated coffee ~1 h before
et al., 1993). However, these changes do not
exercise, exercise for 1-1.5 h and produce a
appear to dampen the ergogenic effect of 9
point of view may be popular because caf-
feine use is prevalent in society, and ath-
approach the urinary caffeine limit. It is not
increased in all subjects in two studies in
letes will not have "illegal" amounts in their
easy to reach the limit by ingesting coffee.
which both users and non-users of caffeine
A caffeine level above 12 µg/mL suggests
moderation is a trivial issue; other drugs
that an individual has deliberately taken caf-
feine in the form of tablets or suppositories
(Graham & Spriet, 1991; Spriet et al.,
greater attention. Nevertheless, the potential
in an attempt to improve performance. Not
ergogenic effect of caffeine is impressive.
surprisingly, only a few athletes have been
caught with illegal caffeine levels during
with more non-users (Graham & Spriet,
use counteracts the "win-at-all-costs" men-
competitions, although formal reports of the
1995). In addition, Van Soeren et al. (1993)
tality and sets the proper example for youth.
frequency of caffeine abuse are rare. One
recently reported that prior caffeine with-
older study reported that 26/775 cyclists had
drawal for up to 4 d did not affect exercise-
illegal urinary caffeine levels when tested
aged 11-18 reported using caffeine in the
prior year to help them do better in sports.
ingested caffeine doses of 6 or 9 mg/kg.
Urinary Caffeine and Doping
determine caffeine abuse in sport has been
criticized. Only 0.5-3% of orally ingested
caffeine actually reaches the urine because
most of the caffeine is metabolized in the
Caffeine and High Carbohydrate Diets
weight) prior to exercise often increases
excreted are not measured in doping tests.
cycling and running in a laboratory setting.
Other factors also affect the amount of caf-
feine that reaches the urine, including body
FFA following caffeine ingestion during 2 h
weight, gender, and hydration status of the
athlete. The time elapsed between caffeine
increase short-term intense cycling (~5 min)
important and will be affected by the exer-
negate the ergogenic effects of caffeine,
cise duration and environmental conditions.
generally reported in well-trained elite or
diet and a pre-trial carbohydrate meal did
recreational athletes, but field studies are
people caught with illegal levels of caffeine
not prevent caffeine-induced increases in
lacking to confirm the ergogenic effects of
will have used caffeine in a doping manner.
performance in a number of recent studies
caffeine in the athletic world. The mecha-
using well-trained/recreational runners and
nisms for the improved endurance have not
metabolizes caffeine slowly or who excretes
could produce IOC-illegal amounts of uri-
Diuretic Effect of Caffeine
effects of caffeine on muscles and/or on the
nary caffeine following ingestion of a mod-
been suggested that caffeine ingestion may
Variability of Caffeine Responses
lead to poor hydration status prior to andduring exercise. However, two studies
metabolic responses to caffeine is large.
sweat loss, or plasma volume during exer-
cise following caffeine ingestion (Falk et
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백삼 및 홍삼 농축액의 사포닌 분석 고성권* 이충렬 최용의 임병옥 성종환 윤광로 중앙대학교 인삼산업연구센터, ㈜일화 중앙연구소, 중앙대학교 식품공학과 Analysis of Ginsenosides of White and Red Ginseng Concentrates Sung Kwon Ko*, Chung Ryul Lee, Yong Eui Choi, Byung Ok Im, Korea Ginseng Institute, Chung-Ang University 1 Ilhwa Co. Ltd.
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