Caffeine attenuates early post-exercise hypotension in middle-aged subjects

Background: Sustained hypotension after an acute dynamic exercise bout is due primarily to peripheral vasodilation. We tested the hypothesis that adenosine-mediated vasodilation contributes to hypotension after exercise, by determining the effect of blocking its actions with caffeine. Methods: Fourteen healthy middle-aged subjects (mean age = 51 +/- 3 years), cycled to peak effort on 2 study days, after a randomized double-blind intravenous infusion of caffeine (4 mg/kg) selective for adenosine receptor blockade, or vehicle. Both studies were performed after 72 h of caffeine abstinence. Results: Infusion achieved 52.0 +/- 6.1 mu mol/L caffeine in plasma. Significant reductions in mean and diastolic blood pressure (BP) were elicited by prior exercise on the vehicle day (from 93 +/- 2 to 85 +/- 2 mm Hg v from 79 +/- 2 to 73 +/- 3 mm Hg, respectively; both P <.05), but not after caffeine infusion. Systolic and mean BP, 10 min after exercise, were higher on the caffeine than on the vehicle day (by 9 +/- 3 and 6 +/- 2 mm Hg, respectively; P <.05), as was heart rate (HR) (100 +/- 5 v 93 +/- 4 beats/min; P <.05). Conclusions: These data suggest that endogenous adenosine contributes to early hypotension after exercise in healthy middle-aged subjects and underscore the importance of caffeine abstinence if BP or HR immediately after exercise is used to infer cardiovascular risk.