Caffeine is found in many foods and drinks, but is most often consumed in the form of coffee, tea, sodas and energy drinks. Studies have shown that caffeine targets the brain and nervous system during exercise, helping to resist fatigue. However, caffeine must be used properly in order to prevent adverse side effects.
Caffeine benefits with exercise max out at 3g of caffeine per kilogram of body weight. The average cup of coffee has anywhere from 100-200g of caffeine. So, most people won't need more than a cup or two of coffee to reach this amount. Remember that not everyone responds the same way so you need to test lesser amounts first.
It has also been determined that caffeine peaks in the bloodstream in 10-30 minutes. You would want to time your caffeine intake to achieve this peak during your workout or directly before depending on the length of exercise. Remember that caffeine is a mild diuretic (meaning that it increases the production of urine) so you must insure that you are drinking enough hydrating fluid throughout the day.
This doesn’t mean that you need to increase your caffeine consumption to get exercise benefits, but it is helpful to know if you are interested in seeing it's affects on your exercise performance.