Caffeine as an Endurance Supplement

author : AMSSM

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The consensus is that caffeine does enhance performance and decreases perceived exertion in endurance exercise. There are no significant performance benefits in short, high-intensity exercise.

By Marjie Delo

Member AMSSM

Caffeine is the most widely used stimulant in the world. A growing body of research also supports caffeine as an ergogenic aid—a chemical that can enhance athletic performance. As early as the 1970s, research from the Human Performance Laboratory at Ball State University suggested that 200 mg of caffeine exerted significant effects on endurance in athletes. Since then, more than 74 well designed studies have been performed on the use of caffeine. The consensus is that caffeine does enhance performance and decreases perceived exertion in endurance exercise. The most dramatic performance improvements are seen during training or races that last from 30 minutes to two hours. There are no significant performance benefits in short, high-intensity exercise.

The mechanism of caffeine's performance enhancement remains controversial. There are three main mechanisms under research. The first is that caffeine stimulates the breakdown of fat, allowing the body to use it as fuel early in exercise. This spares muscle glycogen (carbohydrate stores), allowing the body to save energy for later in the workout and delaying the onset of fatigue. The second theory is that caffeine's effects are due to stimulation of the central nervous system. Stimulation of the CNS leads to decreased perceived exertion, increased adrenaline secretion, increased alertness, and increased mood. The third theory is that caffeine works by improvement of skeletal muscle performance. Caffeine may lead to a lowered blood potassium level, and an elevated muscle calcium level, both of which can help maximize muscle contraction and force generation. None of these theories alone explains the ergogenic effects of caffeine. More likely, it is a combination of physiologic effects that lead to the benefit.
 

The optimal time to load caffeine ranges between studies from 15 to 50 minutes prior to the event. Peak blood levels occur 45-60 minutes after ingestion. The American College of Sports Medicine (ACSM) recommends target doses in the range of 100-300 mg (2-5 mg per kilogram body weight). A cup of coffee has about 150 mg of caffeine, while a ClifShot has 20 mg, and PowerGel has 25-50 mg. Most of the studies have been done with caffeine ingestion prior to exercise. However, recent studies are suggesting that taking caffeine during exercise may still give ergogenic benefits. There is variability between athletes and their response to caffeine; thus, an athlete should experiment to find out what dose and timing work for them.

Athletes are often concerned about dehydration when caffeine is taken with exercise. Studies have shown, however, that there is no change in body hydration during exercise following caffeine intake. Side effects can include heartburn, insomnia, and anxiety. Withdrawal can occur in habitual users, leading to headache and fatigue. Tolerance can develop to caffeine's effects on heart rate, blood pressure, and sleep onset. Luckily, tolerance does not seem to develop to the ergogenic effects on running and cycling performance!

In summary, caffeine has been proven to boost athletic performance and decrease perceived exertion in endurance efforts between 30 minutes and two hours. There is no specific information related to ultra-endurance events. More research will have to be done at these distances to determine whether there is a beneficial effect.

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date: July 9, 2007