Introduction: Caffeine is the most widely consumed physiological stimulant which is consumed via natural sources, such as coffee and tea as an energetic drink and dietary supplement.  The present study was conducted to identify the effect of different doses of caffeine on time to exhaustion, resting level and cardiovascular responses in male athletes.
Methods: Eight male student athletes targeted and were randomly divided into three groups of control, dose of 2.5 mg/ kg caffeine, and dose of 5 mg/ kg caffeine, in a crossover design. Exercise protocol included exhausting running on treadmill (Using Bruce test). Blood pressure (BP), HR and RPP (rate pressure product) was measured before and 1 hour after taking caffeine and immediately after exercise. The data was analyzed using the Shapiro-Wilk, ANOVA with repeated measures (at significance level of 0.05) and Bonferroni post-hoc tests (at significance level of 0.0167).
Results: The data showed that taking both doses of 2.5 mg/ kg and 5 mg/ kg caffeine significantly increased time to exhaustion (P≤0.0167). In addition, dose 5 mg/ kg caffeine significantly Increase systolic blood pressure and RPP at rest, heart rate, systolic blood pressure and RPP at immediately after to exhaustion (P≤0.0167).
Conclusion: It seems that male athletes can increase/improve the time to exhaustion by consuming 2.5 mg/ kg of caffeine supplements without deleterious side effects of cardiovascular instead of 5 mg/ kg 1 hour before exercise. Further researches are necessary, to draw firm conclusions.