Relationships between time of day and variation of blood pressure response to aerobic exercise

Aim: Physical exercise is widely used in primary and secondary prevention of hypertension. National and international guidelines recommend type, frequency, intensity, duration and energy expenditure of exercise, but suggest nothing about the time of day for exercise. This study investigated blood pressure response during aerobic exercise and 30 min of recovery according to time of day. Methods: Twenty-eight sedentary male university students (25±2 yrs) underwent a physical fitness examination before entering the study. Subjects took part in 3 training sessions scheduled 1 week apart at 3 different times of day (9.30 AM; 2 PM; and 6.30 PM). Training was performed on a Recumbent Bike. Each session consisted of 10 min of warm-up at 55%HRmax, 35 min at 70%HRmax, 5 min of cool-down, followed by 30 min of recovery while sitting on the bike. Blood pressure and ratings of perceived exertion were measured during training; during recovery, blood pressure only was measured. Results: ANOVA for repeated measures showed a best trend of diastolic blood pressure during training and recovery when exercise was performed at 6.30 PM. Ratings of perceived exertion were higher during the morning session. No differences were noted for in systolic blood pressure trends. Conclusions. Early evening physical exercise seems to optimize its positive effect on the reduction of diastolic blood pressure.