Some studies show that sustained daily use of caffeine can blunt some of the physiological responses following caffeine intake,[1][2][3][4][5][6] and may reduce its exercise performance-enhancing effects.[7][8][9] Therefore, habitual caffeine users may experience a lower performance-enhancing effect than nonhabitual users. However, not all studies find this “tolerance effect”,[10][11] and a recent meta-analysis concludes that caffeine improves exercise performance even in habitual caffeine users.[12]
It has been suggested that athletes who regularly use caffeine and are seeking performance benefits could take a slightly higher dose before exercise.[13] Another solution would be for athletes to abstain from caffeine intake in the days before a competition to remove tolerance and thereby exploit the performance-enhancing effects of pre-exercise caffeine intake. However, this approach is not recommended because withdrawing from caffeine can increase a person's susceptibility to the unwanted side effects of caffeine.[13] Given the between-person variability in the response to caffeine (both benefits and side effects), the preferred solution is for athletes to experiment with caffeine doses and timing before competition day.[13]