The acute post-exercise response of blood pressure varies with time of day

Abstract

The reactivity of ambulatory blood pressure following a given change in everyday physical activities is highest in the morning. Whether the acute response of blood pressure following a controlled bout of steady-state exercise is influenced by time of day is examined in this study. After 45 min of supine rest, 12 male normotensives completed 30 min of cycling at 70% VO(2peak) which began at either 0800 or 1600 hours. Arterial blood pressure, cardiac output, total peripheral resistance, cutaneous blood flow and temperature were determined before, and up to 90 min after, exercise. Mean +/- SE arterial pressure, averaged over the acute (20-min) period, reduced by 7 +/- 2 mmHg following exercise at 1600 hours but increased by 3 +/- 3 mmHg following exercise at 0800 hours (P = 0.03). Total peripheral resistance fell by 4.2 +/- 0.8 mmHg l(-1) min(-1) after exercise at 1600 hour, but increased slightly by 0.1 +/- 0.5 mmHg l(-1) min(-1) after morning exercise (P = 0.02). We conclude that the acutely hypotensive effects following 30 min of steady state exercise are less marked in the morning, probably because the exercise-mediated decrease in peripheral resistance is not as apparent at this time of day.

Effect of fractionized vs continuous, single-session exercise on blood pressure in adults

“…2 The lack of a BP reduction after the 1 Â 30-min exercise session could be due to inconsistent PEH responses in normotensives or to exercise timing. 2,10,11 Although PEH has been observed in normotensives immediately after exercise, 2 lower BP throughout the day after a morning exercise session was observed in hypertensives, but not in normotensives. 10 In fact, preexercise resting BP is a significant predictor of PEH.…”

“…11 In addition, Jones et al 12 reported a greater postexercise arterial luminal shear rate and blood velocity after morning vs afternoon exercise, which was associated with differences in PEH. 11 This may explain why we observed reduced SBP only after the second and third 10-min exercise sessions (Figure 1). Body posture during BP measurements was not rigorously controlled, although subjects were always either seated or semi-recumbent in a hospital bed during BP measurements.…”

“…2 In addition, exercise in the afternoon has a more potent PEH effect than exercise in the morning. 7,11 In the studies by Jones et al 7,11 PEH was assessed for only 20 min after exercise. Nevertheless, our results may be in part due to the timing of exercise.…”

Blood pressure status and post-exercise hypotension: an example of a spurious correlation in hypertension research?

“…These findings are consistent with recent data from crossover-type experiments that indicated the presence of diurnal variation in the acute BP response after continuous exercise. [36][37][38] A consistent finding is that the reduction in MAP from baseline is greater when exercise begins in the afternoon compared with the early morning. The higher post-exercise MAP in the morning is consistent with the well-documented morning surge in BP implicated in the morning peak incidence of cardiac events.…”

“…39,40 It would appear that diurnal variation in post-exercise total peripheral resistance is important in explaining the higher BP after morning exercise. 36 Time of day effects on PEH may also help to explain some of the discrepancies in findings between previous studies.…”