Protocol for a pilot study to assess the feasibility of interrupting prolonged sitting in the evening with activity breaks in a group of free-living adults.

BACKGROUND: Greater time spent sedentary, particularly when accumulated in long, uninterrupted bouts, is associated with poorer cardiometabolic health and an increased risk of disease incidence and mortality. Experimental studies have indicated that regularly interrupting sedentary time during the day, and more recently, in the evening, with acute (2-5 min) bouts of activity improves postprandial metabolism in a range of adult populations. The effects of interrupting evening sitting time have yet to be explored in a free-living setting. Drawing on the Behaviour Change Wheel and participant-identified barriers and facilitators, the regular activity breaks (RAB) intervention was designed to support participants in interrupting evening prolonged sitting. This pilot and feasibility study will explore the feasibility of this intervention and its effects on 24-h movement patterns, glycemic control, and blood pressure. Results from this study will inform the development of a future effectiveness trial. METHODS: This 4-week, single-group intervention trial consists of a baseline, a 2-week intervention, and a 2-week follow-up period. A total of 20 adults, ≥ 18 years who self-report habitually sitting for at least 3 h in the evening, have a smartphone, and can ambulate unaided will be recruited to participate. The RAB intervention aims to support participants to regularly (~ every 30 min) perform short bouts (2-3 min) of activity during periods of prolonged sitting in the evening. The intervention components include (1) a structured consultation with the study coach where behaviour change techniques will be used to create an individualised plan for performing activity breaks in the evening; (2) provision of a mobile application to provide scheduled reminders and activity break videos; and (3) follow-up support in the form of phone calls performed on days 3 and 7. Feasibility will be assessed by meeting recruitment and retention targets; the acceptability of the intervention will be assessed via semi-structured interviews. Pilot outcomes include the number of activity breaks performed, impact on 24-h movement patterns (sleep duration and quality, sedentary time, and physical activity), blood pressure, interstitial glycemic response, mobile application engagement and capability, and opportunity and motivation to change evening sitting behaviour. DISCUSSION: Should the RAB intervention meet the criteria to be deemed feasible and acceptable, this will provide justification and information for its use in a large-scale effectiveness trial. TRIAL REGISTRATION: This study is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR 12624000371594). Registered March 28, 2024.