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.
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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