Caffeine enters the bloodstream within minutes after consumption, and reaches its peak level in about 30 minutes. One caution to be pointed out is that the side effects of nervousness and dehydration may very well offset any benefits that may occur due to increased workload. Studies have supported the conclusion that athletes involved in strength and power sports, such as strength training or sprinting, have shown no improvement due to taking caffeine. Caffeine induced dehydration may actually decrease athletic performance by decreasing the efficiency of the muscles which are forced to work while being deprived of fluids. As athletes drink their caffeinated beverages, they need to be aware that caffeine rarely has any positive affects on athletic performance, but may very well have a negative impact on their overall heath and performance.
Caffeine addiction does exist.
Withdrawal symptoms such as headaches, irritability, fatigue and upset stomach may occur, within 12 hours after the last ingestion. The side effects of caffeine use outweigh any possible benefits the athlete may be seeking.