Because caffeine enhances performance in many individuals, it has been banned by the International Olympic Committee. But ironically, the level at which caffeine is banned far exceeds the amount needed to enhance performance. Higher, illegal levels are generally attained with caffeine supplements, since a 150-pound athlete would need to drink 3 to 4 large cups of coffee within an hour before activity to reach the upper acceptable limit. Habitual caffeine consumers experience less ergogenic effect than people who consume it rarely. For the optimal ergogenic benefit, the trick may be to use caffeine strategically at certain points to allow for harder training, and then discontinue it to avoid developing a tolerance.
Caffeine affects each person's performance differently.
Thus it appears that caffeine does not increase urine production during exercise. However, responses to caffeine vary, so you should base your preexercise consumption on how caffeine affects your body. After exercise, caffeine is a poor choice for fluid replacement. The safest bet is to tank up on noncaffeineated beverages just after activity, and then later, if you so desire, enjoy your favorite caffeinated beverage in moderation. Caffeine and exercise performance.