Caffeine has been shown in several studies to enhance endurance performance, possibly by increasing use of fat as a fuel. Less work has been done in high-intensity exercise that requires more muscle strength and power. Because caffeine works through multiple mechanism, it is possible that it could also benefit higher intensity exercise. Australian researchers examined the effects of a single dose of caffeine on intense, intermittent exercise performance. Healthy men performed an exercise test 60 min after consuming caffeine or placebo. The dose of caffeine was 6 mg/kg body weight (450 mg for a 165 pound man), which is equal to about 2-3 cups of coffee. The performance test consisted of a variety of sprints with short rest periods on a cycle. The results showed a clear benefit of caffeine over placebo with subjects showing a 7-8% increase in peak power and total work achieved during the intermittent sprinting task. The benefits of caffeine could be due to central nervous system facilitation or decreased perception of fatigue. The findings support the idea that a couple cups of coffee or a supplement containing caffeine before a workout has the potential to increase exercise intensity.

Schneiker KT, Bishop D, Dawson B, Hackett LP. Effects of Caffeine on Prolonged Intermittent-Sprint Ability in Team-Sport Athletes. Med Sci Sports Exerc. 2006 Mar;38(3):578-585.