Coffee was first discovered over 1000 years ago, and
currently approximately 75% of Americans drink coffee on a
regular basis. Despite the thousand years that have passed,
there is still mystery and controversy surrounding the biological
effects of coffee and it's active principal ingredient; caffeine.
Caffeine is the most widely used stimulant 'drug' in the world,
usually ingested in the form of coffee, tea, soft-drinks, and
chocolate. Caffeine is also used by triathletes and other
athletes as a performance aid. The purpose of this article is to
discuss the role of caffeine as an ergogenic (energy
generating) aid in endurance sports and to discuss the health
issues, such as cardio respiratory, related to caffeine use.
What happens when caffeine enters the body?
Caffeine is well absorbed from by the stomach and intestine,
and peak blood levels occur about 45 - 60 minutes after
ingestion. Once in the blood stream, caffeine causes a
number of responses in the body. Caffeine is well known for
it's stimulant effects on the brain, but there are a number of
other physiologic effects that occur. Blood pressure, pulse
rate, and stomach acid production are increased, fat stores
are broken down, and fatty acids are released into the blood
stream. These effects can last from a few hours to as long as
12, but within 4 days of regular use, the body develops
tolerance to many of the effects of caffeine.
For example, caffeine increases blood pressure and pulse rate in a first
time user, but a regular user will not experience any significant
alterations in comparison.
Caffeine and Health
In making a decision whether or not to use caffeine -- or any
other drug -- it is important to consider the potential adverse
effects it may have on your personal health. These can be separated into short term (i.e.
related to a single dose) and long term.
The short term affects of caffeine are much better understood than the long term
effects. Because caffeine increases the production of stomach acid it
may worsen ulcer symptoms or cause acid reflux
("heartburn"). Insomnia, poor sleep, and anxiety are well
described psychological side effects of caffeine use. Regular
evening use of caffeine may, over time, deprive the body of
proper sleep, resulting in lack of energy and fatigue.
Many studies have suggested a relationship between chronic
caffeine use and a number of diseases. Proving a cause-and effect,
however, has been difficult and most of these
suggested links remain inconclusive. Some of the difficulties
that arise in studying the long term health effects of caffeine
are due to problems in accounting for other lifestyle variables
(eg. smoking, alcohol consumption, exercise), differences in
genetic inheritance, form of caffeine intake (coffee, tea,
sodas), and the presence of other biologically active
substances in the beverage.
For example, one study looked at whether or not caffeine intake increased
the risk of heart disease. Over 45,000 people were evaluated and the data
indicated a slightly increased risk of death from heart disease
in individuals who had an average daily consumption of more
than 5 cups of *decaffeinated* coffee. Currently, there is no
evidence that caffeine causes cancer, stomach ulcers, high
blood pressure, or serious heart arrhythmia.
Caffeine Withdrawal
Abrupt discontinuation of caffeine in a regular user may trigger
caffeine withdrawal symptoms. The most common symptoms
are headache and fatigue. The headache may begin as soon
as 18 hours following the last dose of caffeine and may
worsen with exercise. It is not known why some people
experience caffeine withdrawal and others do not.
Caffeine and Athletic Performance
Despite considerable research in this area, the role of caffeine
as a performance enhancing drug is still controversial. Some
of the data are conflicting, which is in part due to how the
experimental studies were designed and what methods were
used. However, there is general agreement in a few areas:
Caffeine does not appear to benefit short term, high intensity
exercise (eg. sprinting).
Caffeine can enhance performance in endurance sports.
Glycogen is the principal fuel for muscles and exhaustion
occurs when it is depleted. A secondary fuel, which is much
more abundant, is fat. As long as there is still glycogen
available, working muscles can utilize fat. Caffeine mobilizes
fat stores and encourages working muscles to use fat as a
fuel. This delays the depletion of muscle glycogen and allows
for a prolongation of exercise. The critical time period in
glycogen sparing appears to occur during the first 15 minutes
of exercise, where caffeine has been shown to decrease
glycogen utilization by as much as 50%. Glycogen saved at
the beginning is thus available during the later stages of
exercise. Although the exact method by which caffeine does
this is still unclear, caffeine caused sparing in all of the human
studies where muscle glycogen levels were measured. The
effect on performance, which was observed in most
experimental studies, was that subjects were able to exercise
longer until exhaustion occurred.
In addition to the beneficial effects on muscle, caffeine may
alter the perception of how hard you are working. During
testing, athletes are asked to judge their effort, which is
referred to as the rating of perceived exertion (RPE). Some
studies have yielded significantly lower RPE's -- less fatigue --
when the athlete used caffeine. Other studies have not found
this effect. Obviously, the RPE is very subjective, and there
are many things that may influence it.
What about caffeine in Ironman races?
The exercise studies on caffeine involved endurance testing of
approximately 2 hours, so there is no specific information
related to ultra-endurance races. Pre-race caffeine may be
beneficial though, because the longer the race, the more
important fat is as a fuel. During the race, caffeinated soft
drinks are one of the choices at the aid stations in an Ironman race.
Whether this source of caffeine is useful or not remains unknown, but these
soft-drinks do supply the individual with the necessary carbohydrates. Because longer
races have a greater baseline risk of dehydration, nausea and
abdominal cramps, it is very important to consider the side
effects of caffeine (below).
Variable results and side effects.
Despite the known benefits of caffeine in endurance exercise,
individual results may vary greatly. Differences in metabolism,
diet, and frequency of caffeine use are some of the factors
that can determine how an individual will react to caffeine.
Additionally, some athletes may actually experience a
decrease in performance, usually due to side effects of
caffeine.
Although caffeine does not appear to significantly alter water
balance or body temperature during exercise, dehydration is a
potential concern because caffeine is a mild diuretic. Some
athletes may also experience abdominal cramps and diarrhea
related to the large intestine contractions caused by caffeine.
The combination of dehydration and cramping can have
particularly detrimental effects on performance.
What about drug testing?
The International Olympic Committee currently lists caffeine as
a restricted drug. Urinary levels up to a concentration of12
mg/liter are acceptable, representing casual use. Levels
above this are viewed as achieved through a deliberate
attempt at doping by the athlete. Approximately 1000mg of
caffeine (about 8 cups of coffee) would be required to exceed
the current IOC limit, but it is very important to note that
people can metabolize caffeine at very different rates.
Differences in metabolism, medications, and certain diseases
may significantly alter the rate in which caffeine is cleared from
the body. Some athletes have come close to flunking the drug
test after ingesting only 350mg. It is wise to consider this
before using caffeine as an ergogenic aid.
Recommendations for athletes
If you choose to use caffeine, then here are a few tips that
may help you maximize the benefits.
Ingest caffeine about 3 - 4 hours before the competition.
Although blood levels of caffeine peak much sooner, the
maximum caffeine effect on fat stores appears to occur
several hours after peak blood levels.
Consider decreasing or abstaining from caffeine for 3 - 4 days
prior to competition. This allows for tolerance to caffeine to
decrease and helps ensure a maximum effect of caffeine. Be
careful though, because some may experience caffeine
withdrawal.
Make sure that you have used caffeine extensively under a
variety of training conditions and are thoroughly familiar with
how your body reacts to this drug. Never try anything new on
race day.
Be prepared to accept the consequences if your urine test is
above the current cutoff.
Conclusion
In writing this article I am not suggesting that athletes use
caffeine nor am I supporting the use of performance
enhancing drugs. I am simply reviewing the use of caffeine as
an ergogenic aid as well as the known health consequences.
Athletes must individually decide whether or not it is
appropriate to use this drug -- both in competition and day-today.
All of the information for this article came from the current
medical literature. Those of you who take prescription
medications or who are under a physician's care should check
with your doctor about the relevance of caffeine to your health.
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