Effects of A Sit Less and Move More (SLAMM) App on Sedentary and Physical Activity Behaviours

A single-arm 12-week digital intervention study will be conducted using a mobile application-based behaviour change platform called SLAMM (Sit Less And Move More). The intervention combines real-time activity tracking with context-aware, semi-personalised behavioural support. Objectives: To evaluate the feasibility, usability, and preliminary effects of a progressive digital health intervention aimed at reducing sedentary behaviour (SB) and promoting light-to-moderate physical activity (PA). Aims: 1- To assess changes in sedentary behaviour and physical activity over 12 weeks. 2- To evaluate user perceptions of feasibility, usability, and acceptability of the SLAMM intervention. 3- To explore how personalised and contextually adapted behavioural strategies influence daily movement behaviour (sitting time, active time, exercise time). Participants: Participants will be community-dwelling adults who are at high-, medium-high-, medium- or low-medium risk for cardiovascular health. The risk level is determined via a SIT-ACT risk matrix, which considers sedentary hours and physical activity minutes combined. Intervention Components: Participants will be classified into movement behaviour levels (Sit Less, Move More, and Exercise) based on their sedentary and activity levels using a risk assessment tool (i.e. the Sit-Act Matrix). Sit Less Group: receives only Sit Less messages. Move More Group: receives both Sit Less and Move More components. Exercise Group: receives all components, including an exercise program. Participants can progress to a higher group (risk level) on a weekly basis based on their behavioural data captured by the mobile app. Messages include: - Sit Less: Motivational messages to interrupt sitting, adapted to time of day, weather, and work status. - Move More: Prompts encouraging walking or light movement integrated with daily routines. - Exercise: Semi-automated coaching with light-to-moderate intensity exercise prescriptions. Participants will receive up to six messages per day. These messages are designed to prompt behavioural changes and are data-driven, meaning they are triggered by prolonged sitting periods or relevant activity patterns (moving or exercising). Potential time points will include morning, lunchtime, afternoon and evening, Examples of messages: Sit Less: “Stuck inside because of bad weather? Stay active indoors by climbing stairs or pacing between rooms.” Move More: “Been sitting too much? Break up your day with a lunchtime walk with a coworker.” Exercise: “Swimming for 40 minutes from 7:00 to 7:40 am; the intensity level: moderate [select via app].” Exercises prescribed to the Exercise Group include activities such as swimming, or cycling, tailored to light-to-moderate intensity. This will be measured using the Borg Rating of Perceived Exertion (RPE) scale. Adherence: Adherence to the intervention will be assessed by interaction with the app (logging activities and app screen time). App analytics will thus provide ongoing monitoring of participant engagement and intervention fidelity. Technology: Participants will use the SLAMM mobile app, which integrates with Fitbit or a personal activity tracker to collect real-time movement and sedentary data. The app also accesses contextual data (e.g., weather) to deliver adaptive prompts. Decision Logic: Messages are dynamically generated based on participant availability, movement levels, contextual factors, and behavioural trends. Data Collection: Objective data will include sedentary hours. activity minutes, exercise minutes, self-reported questionnaires and post-intervention interviews will assess usability, satisfaction, and behavioural awareness. Sample Size: A total of 38 community-dwelling adults will be recruited to evaluate preliminary effects and feasibility metrics. Results will guide future iterations and a larger-scale randomised trial. Recruitment Timeframe: Start Date: Recruitment is expected to commence in mid-July 2025. End Date: Recruitment will conclude in early July 2026, or once the target sample size of 38 participants is reached, allowing time for replacements if any participant withdraws.