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

Abstract

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.

Acute Effects of Frequent Light-Intensity Standing-Based Exercises That Interrupt 8 Hours of Prolonged Sitting on Postprandial Glucose in Stroke Survivors: A Dose-Escalation Trial

“…A statistical analysis plan was outlined a priori 21 to detect withinperson, between-condition differences in the primary outcome systolic blood pressure. The secondary outcome postprandial glucose is reported as the positive incremental area under the curve (+iAUC).…”

“…This manuscript reports results for the predetermined secondary outcome (postprandial plasma glucose) from a laboratory-based, dose-escalation trial, the methods of which have been previously described. 21 Briefly, stroke survivors recruited from the Newcastle and Hunter region (NSW, Australia) attended the Hunter Medical Research Institute on 4 separate occasions (Figure 1). Participants undertook a familiarization session and three 8-hour conditions in cohorts of 10 participants.…”

The Effects of Interrupting Prolonged Sitting With Frequent Bouts of Light-Intensity Standing Exercises on Blood Pressure in Stroke Survivors: A Dose Escalation Trial

“…Power calculations were conducted a priori and reported in the published protocol paper 21 ; these determined that n = 30 (n = 10/ cohort) would provide sufficient power (80%) to detect a withinperson, between-condition difference in systolic blood pressure of 3.5 mm Hg (assumed SD 15 mm Hg) at the most beneficial dose of STAND-EX. Blood pressure collected during experimental conditions (08:00-16:00) and 24 hours post (16:00-16:00 +1 day ) was analyzed separately.…”

“…These 3 conditions were composed of a control condition (8 h of prolonged sitting) and 2 experimental conditions until a dose limiting threshold was achieved. The published trial protocol 21 details the dose escalation procedure that was to be undertaken. In brief, Cohort 1 would undertake experimental condition 1 (8 h of sitting interrupted by 2 × 5 min bouts of STAND-EX) followed by experimental condition 2 (8 h of sitting interrupted by 4 × 5 min bouts of STAND-EX).…”

“…Cohort 2 would undertake experimental condition 2 followed by experimental condition 3 (8 h of sitting interrupted by 6 × 5 min bouts of STAND-EX). If the dose limiting threshold (detailed in the published protocol 21 ) was attained, a final cohort would repeat the penultimate cohort. However, this study details the modified protocol that was completed due to the COVID-19 pandemic (2020).…”