Invited Paper TIMING OF EXERCISE WITHIN THE WAKING PERIOD DOES NOT ALTER BLOOD PRESSURE DURING SUBSEQUENT NOCTURNAL SLEEP IN NORMOTENSIVE INDIVIDUALS

Exercise can cause a reduction in blood pressure (BP) that is prolonged enough to extend into nocturnal sleep. This post-exercise hypotension has been found to be less apparent in the morning when the immedi-ate (during the 20 minutes after exercise) responses are considered. However, it is currently unknown if the timing of exercise (morning vs. afternoon) mediates different BP responses during a longer follow-up period of everyday habits and nocturnal sleep. Therefore, we aimed to examine BP for up to 24 hours following exercise in the morning and afternoon. After 45 minutes of supine rest, 12 male normotensives completed 30 minutes of cycling at 70 % V O2peak, which began at either 08:00 or 16:00 hours. Between 20 minutes and 24 hours after exercise, ambulatory BP, heart rate and wrist-activity were monitored and compared between trials using general linear models. Participants slept normally at night. Systolic, diastolic and mean arterial BP did not differ between trials from 20 minutes after exercise until nocturnal sleep onset (p> 0.23) or dur-ing the nocturnal sleep period (p> 0.20). During the daytime period, heart rate was 5 beats·min–1 higher fol-lowing morning exercise compared with the afternoon trial (p = 0.05), and physical activity was also greater following morning exercise (p = 0.01). Nocturnal measurements of heart rate and physical activity were unaf-fected by the timing of exercise (p> 0.63). We conclude that the timing of exercise does not moderate subse-quent BP responses during everyday activity and nocturnal sleep in normotensive individuals. These findings suggest that the diurnal variation in BP immediately after exercise is relatively short-lived and does not extend into the nocturnal sleep period. [J Exerc Sci Fit • Vol 7 • No 2 (Suppl) • S42–S50 • 2009