Is Caffeine A Sports Supplement?

Caffeine is America's most popular and socially condoned drug. It stimulates the sympathetic nervous system, which can aid physical performance by directing blood to skeletal muscle and by increasing available fuel (sugars and fats) in the bloodstream.1 Caffeine also increases metabolites and markers of fatigue, but it does not aid recovery.2

Caffeine's effects are most pronounced in nonregular users. In addition, it shows little benefit in events lasting less than 90 seconds, and within 70 to 90 minutes its effects decline. This gives merit to the strategy used by some ultramarathoners who take caffeine during the last hour or so of a race.2

The normal dose of caffeine is between 3 and 10 mg per kilogram body weight, which, for a 150-pound athlete, translates to one to three cups of coffee. Caffeine is banned by the International Olympic Committee, but only when urine levels exceed 12 mcg per millileter of blood. The dose listed above is well under this limit.
1.French C, et al. Caffeine ingestion during exercise to exhaustion in elite distance runners. J Sports Med Phys Fitness 1991 Sep;31(3):425-32.

2.Spriet LL, et al. Caffeine and performance. Int J Sport Nutr 1995 Jun;5 Suppl:S84-99.