Magazine article Drug Topics

Clinical Q&A

Magazine article Drug Topics

Clinical Q&A

Article excerpt

Should creatine be recommended to athletes?

A: Over the past several years, ergogenic supplements, intended to increase work capacity, have gained much popularity among professional and amateur athletes. Creatine has become a leader in this market because of claims that it can enhance performance and reduce fatigue. First marketed in the United States in 1993, creatine has also become very popular among high school and college athletes. Sales jumped from $3 million in 1996 to $25 million in 1997. It is estimated that 800 tons of creatine were sold in 1997. Despite the product's popularity, questions remain regarding its safety.

Creatine is a crystalline nitrogenous compound synthesized in the body (i.e., the liver, pancreas, and kidneys) from the amino acids glycine, arginine, and methionine. It is also found in meat and fish, from which the normal daily intake of creatine is approximately 1 gm. Creatine is stored in skeletal muscle in the form of creatine phosphate, which acts as a precursor to adenosine triphosphate (ATP). Hydrolysis of ATP to adenosine diphosphate (ADP) yields large amounts of free energy that is used by contracting muscles. When creatine is supplemented exogenously, phosphocreatine stores rise, and ATP is replenished faster.

Several studies have evaluated the effect of creatine on physical performance. One researcher evaluated the effects of oral supplementation of creatine on torque production during repeated bouts of maximal high-intensity exercise in males. Subjects were randomized to receive either creatine at 5 gm four times daily or placebo. The creatine group achieved a higher torque level compared with both the predose level and the placebo group.

Other studies have shown that creatine phosphate levels in the muscle can be increased by approximately 20% to 25% and that performance of high-intensity intermittent exercise can be enhanced with creatine supplementation. Most of the 55 studies on athletes reported increased repetitive sprint performance, strength, and muscle endurance. A number of studies reported increased highintensity exercise capacity, anaerobic threshold, and maximal exercise capacity. A study conducted on elite swimmers demonstrated that these athletes were able to cut their 100-meter time by 1 to 1.5 seconds.

However, creatine supplementation has little or no value in anaerobic performance and offers no benefit in endurance activities that last for prolonged periods of time. The reason for that is that ATP synthesis depends on phosphocreatine only for a matter of seconds, after which ATP is produced anaerobically by glycolysis or aerobically by other mechanisms of carbohydrate and fat breakdown. …

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