Breaking up sitting time after stroke - How much less sitting is needed to improve blood pressure after stroke (BUST-BP-Dose): Protocol for a dose-finding study

Excessive sitting is detrimentally associated with cardiovascular disease and all-cause mortality. Frequent breaks in prolonged sitting can improve cardiometabolic responses in non-stroke populations. However, this has not been established in stroke survivors. This study will determine the most effective dose of activity breaks that (i) produce clinically meaningful improvements in mean systolic blood pressure (primary outcome), postprandial glucose, and insulin responses (secondary outcomes), and (ii) is safe and feasible. We hypothesis that systolic blood pressure, postprandial insulin, and glucose responses will improve with increasing doses of activity and be most effective at the maximum safe and feasible dose of activity. Thirty participants in the most effective dose will provide 80% power to detect a within-person, between-condition, difference of 3.5 mmHg in systolic blood pressure assuming a SD of 15 mmHg, within-person correlation of 0.9, and α = 0.05. Stroke survivors will complete 3 experimental conditions in a within-participant, dose escalation design including (i) uninterrupted sitting (8 h), (ii) Dose 1: uninterrupted sitting with bouts of light-intensity exercises while standing (initial dose involves two 5-min breaks), and (iii) Dose 2: two additional 5-min breaks above Dose 1. Ambulatory blood pressure will be collected every 30 min during experimental conditions and hourly for 24-h post-experimental conditions. Blood samples will be collected every 30 min during 2-h postprandial periods. This study will identify the most effective dose of light-intensity exercises while standing to improve cardiometabolic responses in stroke survivors.