Cardiovascular Responses in Prehypertensive Individuals during Dynamic Exercise

It is generally known that in hypertensive individuals, exercise induces exaggerated increase in arterial blood pressure and in turn this dangerous elevation may increase the risks for myocardial infarction, cardiac arrest, or stroke. However, it has still not been investigated whether the exaggerated cardiovascular responses occur in prehypertension and these excessive responses are mediated by exercise pressor reflex overactivity. Therefore, the purpose of this study was to examine the effects of exercise pressor reflex on the cardiovascular responses when exercise intensity increased from rest through low exercise intensity to high exercise intensity. Twenty young, fit people (10 normotension and 10 prehypertension) with normal body fat percentage were recruited for this study. All subjects were instrumented to measure the cardiovascular responses at rest and during exercise. A catheter to collect blood samples was inserted into left brachial vein. Systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure were significantly higher in prehypertension across workloads compared to the normotension. Stroke volume (SV), heart rate (HR), and cardiac output (CO) were significantly increased in both groups with increasing workloads, but SV and CO were significantly higher in prehypertension. There was no difference in total vascular conductance in both groups. Thus, exaggerated blood pressure responses were mediated via increases in CO. This study suggests that the excessive cardiovascular responses to exercise in prehypertension may be due to dysfunction of exercise pressor reflex.