The Effects of Aerobic Exercise Timing on Nocturnal Blood Pressure Dipping in Pre-Hypertensive Individuals

Abstract

During the typical nocturnal sleep cycle, BP will "dip" or decrease when compared to diurnal pressure reducing stress on the cardiac system. Compared with a reference group of normotensive dippers, hypertensive non-dippers may experience a much higher relative risk of cardiovascular mortality than normotensive non-dippers and hypertensive dippers. Post exercise hypotension may augment the dipping response, however, exercise timing on sleep pressures has never been elucidated. Therefore, the purpose of this study was to examine how the timing of aerobic exercise affects circadian ambulatory blood pressure and specifically nocturnal blood pressure. METHODS: Six pre-hypertensive subjects, 4 male and 2 female, (mean age 43 ± 4 years) with no reported cardiac disorders and on no antihypertensive medications participated in this study. Following a graded exercise test during visit 1, subjects reported to the laboratory for 3 additional visits to 3 predetermined exercise times at 7am, 1pm, and 7pm in random order to perform 30 min of treadmill exercise at 65% of their VO2max. An Oscar 2™ ambulatory blood pressure cuff was used to monitor blood pressure responses for the 24 hrs immediately following exercise. RESULTS: Aerobic exercise at 7 pm invoked the greatest dip in nocturnal pressure (SBP: 11.9% drop at 7am vs. 8.4% at 1pm vs. 18.0% at 7pm, DBP: 16.8% drop at 7am vs. 11.9% at 1pm vs. 23.1% at 7pm, p<0.05) than exercise in the afternoon or morning time slots. CONCLUSION: Moderate intensity, aerobic exercise in the evening may be the most beneficial epoch of time for greater nocturnal blood pressure dipping for a pre-hypertensive cohort. This study was sponsored by a grant from Appalachian State Office of Student Research (PI, Ben Cartner)