Caffeine is a stimulant and is used in many thermogenic formulas to increase metabolic rate. Caffeine also increase fat breakdown and use of fat as a fuel during rest and exercise. In terms of athletes, there exists a large number of studies that have evaluated the effects caffeine on prolonged endurance performance. Several studies show greater use of fat as a fuel, sparing of glycogen use during exercise, and enhanced endurance performance. However, there are fewer studies examining short-term exercise performance such as sprinting. One study had athletes perform repeated sprints one hour after either caffeine ingestion or placebo. The dose of caffeine was 6 mg/kg body weight (about 450-500 mg of caffeine) which is equivalent to 3-4 cups of brewed coffee. Times during 5 sets of 6 x 20 m sprints were significantly faster after caffeine and reaction times, and there was also a trend for improved reaction times. The findings indicate that in addition to prolonged endurance performance, acute caffeine ingestion can also significantly improve sprint performance.

Carr A, Dawson B, Schneiker K, Goodman C, Lay B. Effect of caffeine supplementation on repeated sprint running performance. J Sports Med Phys Fitness. 2008 Dec;48(4):472-8.