Caffeine and exercise performance:
Caffeine prolonged time to exhaustion in cycling possibly by conserving potassium. Caffeine Researchers examined the effects of caffeine on athletic performance, including oxygen uptake, also known as VO2 max; oxygen deficit; and certain substances that are by-products of exercise. The researchers evaluated six trained cyclists who exercised to a level beyond aerobic capacity—the ability of the body to utilize oxygen—following consumption of 5 mg per kilogram of body weight of caffeine. There was a significant increase in exercise endurance of 14.8% and the ability of the athletes to exceed aerobic capacity by 6.5%; however, no change was observed for maximum oxygen uptake. Blood potassium levels were tested as a measure of metabolic efficiency and found to be decreased after caffeine consumption and prior to exercise by 13.4%, leading the researchers to suggest the possibility that caffeine had a conserving effect on potassium, thereby prolonging time to fatigue. (5)
