Time of day (TOD) for exercise may influence blood pressure (BP) reduction in hypertension because of the diurnal variation of BP and the duration of BP reduction following a single bout of exercise. The purpose of this study was to observe the effects of TOD for exercise on ambulatory blood pressure reduction in dipping (n=5) and nondipping (n=9) hypertension (<10% drop in nighttime BP (BP(night))).
Hypotheses: (1) evening exercise (PM(ex)) would exhibit a greater BP(night) reduction in Non-Dippers than Dippers, (2) morning exercise (AM(ex)) would exhibit similar daytime BP (BP(day)) reduction in Dippers and Non-Dippers, (3) AM(ex) would exhibit greater 24 h BP (BP(24 h)) reduction than PM(ex) in Dippers, and (4) AM(ex) and PM(ex) would exhibit similar BP(24 h) reduction in Non-Dippers. BP responses to AM(ex) (0600-0800 h; 30 min at 50% VO(2peak)) and PM(ex) (1700-1900 h) were compared to each control day in a randomized design. Systolic (S) and diastolic (D) BP were averaged for BP(24 h), BP(day), and BP(night). A two-way ANOVA (dipping X time of exercise) using BP reduction with repeated measures were performed at P<0.05.
Findings: (1) Non-Dippers respond to exercise despite of TOD for exercise, (2) PM(ex) exhibited a greater SBP(night) reduction in Non-Dippers than Dippers, (3) AM(ex) exhibited similar SBP(day) reductions in Dippers and Non-Dippers, and (4) AM(ex) and PM(ex) exhibited similar SBP(24 h) reduction in Dippers and Non-Dippers. Dippers and Non-Dippers respond differently to TOD for exercise. The duration of the BP reduction persists up to 24 h after exercise.