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Caffeine is one of the most widely used stimulants in the
world. It occurs naturally in the foods and beverages such
as coffee, tea, soft drinks, chocolate and cocoa. The average
caffeine consumption in the United States is approximately
200 mg or equivalent to 2 cups of coffee a day. Ten percent
of the population ingests more than 1000 mg per day. Caffeine
is also added to several over-the-counter medicines such as
some weight-loss products, pain medicines, and cold remedies.
Caffeine is a legal and socially acceptable drug consumed
throughout society. Caffeine is often referred to as a nutritional
ergogenic aid, however it has no nutritional value. Ingested
caffeine is quickly absorbed from the stomach, with peaks
in the blood occurring within 1-2 hours.
Caffeine is absorbed by most of the body’s tissues;
it therefore has the potential to affect all systems of the
body. All the excess caffeine is broken down in the liver,
with the byproducts being excreted in urine.
Caffeine supplementation &
Athletic Performance
Improvements have been shown in athletes that perform
short-term intense (near maximal) exercise lasting approximately
five minutes. The reason may be a direct effect of caffeine
on muscle contraction during anaerobic exercise.
The common explanation to why endurance is improved with
caffeine is that muscle glycogen is spared. Glycogen is
the stored energy in the muscle tissue that is broken
down during exercise. Studies suggest that glycogen sparing
may occur as a result of caffeine's ability to increased
the release of adrenaline (epinephrine) into the blood,
thus stimulating the release of free-fatty acids from
skeletal muscle/fat tissue. It is important to note, however
that studies cannot fully explain the ergogenic effect
of caffeine. |
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Put into the context of exercise, this meant that exercising
muscles were able to use the additional fat during the initial
stages of exercise, thus decreasing the initial depletion
of muscle glycogen (carbohydrate). This ‘glycogen sparing’
resulted in more being spared for the latter stages of exercise,
theoretically delaying the onset of fatigue.
More recent research performed in a controlled laboratory
setting showed that the ingestion of 3-9mg of caffeine per
kilogram (kg) of body weight (bw) 1 hour prior to exercise,
resulted in an increased level of performance in running and
cycling. In real terms 3mg per kg/bw would equate to approximately
2 cups of coffee.
There is still a lack of a conclusive theory to describe the
observed ergogenic affects associated with caffeine consumption.
Glycogen sparing does occur after caffeine ingestion (5-9mg
per kg/bw) in the early stages of submaximal exercise; however
this cannot be conclusively attributed to caffeine’s
ability elevate the fat availability for use within the skeletal
muscle. Caffeine supplementation at a low dosage (3mg per
kg/bw) does not have any supporting evidence for a metabolic
component responsible for enhancing physical performance.
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.
Caffeine 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.
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