Purpose: To compare the acute effects of intermittent physical activity (PA) across 4 different intensities on blood pressure.
Methods: Thirty children (12 males and 18 females; aged 7-11 y; 33% overweight/obese; 53% nonwhite) completed 4 experimental conditions in random order: 8 hours sitting interrupted with 20, 2-minute low-, moderate-, high-intensity PA breaks, or sedentary screen-time breaks. PA intensity corresponded with 25%, 50%, and 75% of heart rate reserve. Blood pressure was measured during each condition in the morning (0800 h), noon (1200 h), and afternoon (1600 h).
Results: There were no significant differences across conditions for systolic blood pressure (SBP; all Ps > .05). There was a significant effect of time with SBP decreasing throughout the day for all conditions (average morning SBP: 106  mm Hg, average noon SBP: 101  mm Hg, average afternoon SBP: 103  mm Hg; P = .01). There were no significant effects of condition or time on diastolic blood pressure (all Ps > .05).
Conclusion: While sedentary behavior is known to be associated with hypertension in both adults and children, a single bout of prolonged sitting may be insufficient to produce hypertensive effects in otherwise healthy children. Future research should examine the appropriate dose of intermittent PA to accrue hypotensive responses in preadolescent children.
Trial registration: ClinicalTrials.gov NCT02831309.
Keywords: activity breaks; exercise; hypertension; sedentary time.