Influence of Regular Exercise Training on Post-exercise Hemodynamic Regulation to Orthostatic Challenge

To prevent orthostatic hypotension, arterial blood pressure (BP) is neurally and hormonally regulated via increases in heart rate (HR) and peripheral vascular tone. After dynamic exercise, however, the latter arm is blunted because of the increased vasodilators in exercised muscles. Orthostatic tachycardia is likely a more important compensatory mechanism for post-exercise orthostatic intolerance in individuals who have higher leg vasodilator capacity, such as endurance-trained athletes. To test the hypothesis that regular endurance training was associated with the greater augmentation of tachycardia response to post-exercise orthostasis, we compared hemodynamic responses to 5-min 60-degree head-up tilt (HUT) before and after 60 min of cycling at 70% of HR reserve in the endurance-trained (n=8) and sedentary men (n=9). Calf peak vascular conductance was 62% greater in the endurance-trained than the sedentary (P