The difficulty is that there are considerable differences among individuals regarding their sensitivity to caffeine. Also, such factors as dosage, intensity and duration of exercise, type of exercise, and level of fitness all play a critical role. The best that can be said at this time is that caffeine may help improve the performance of selected individuals who are most susceptible to its effect. Given the evidence, it may be worth trying. There are, however, trade-offs that you will have to deal with.
Beverages containing caffeine stimulate the flow of urine.
This can cause discomfort or decrease the body's fluid. The latter can be dangerous, particularly during long races or when training in hot weather. Caffeine before competition may hamper performance by heightening anxiety and causing nervousness.