A smartphone-based real time and adaptive intervention to encourage people with type 2 diabetes sit less and move more

A micro-randomised trial (MRT) will be conducted. Intervention duration will be 42 days continuously. Objectives: To evaluate a smartphone-based just-in-time adaptive intervention (JITAI) to interrupt sedentary behaviour (SB) and promote physical activity (PA). Aims: 1- To assess the proximal and distal effects of each intervention component. 2- To identify how the effect of the intervention changes over time. 3- To identify factors (e.g., contextual) that moderate the effect of intervention components. Randomization: The following probabilities is used for randomization: 70% in the intervention (35% Sit Less, 35% Move More) and 30% as active control at that particular decision point (please see below). Procedure: A user-friendly Android smartphone app (called iMove) and a prototype activity tracker developed by our team will be used. Motivational messages, in the form of notifications, will be used as “intervention components”. The length of intervention messages will be varied taking between 8 to 15 seconds read. There will be 2 “intervention options”; a sedentary interruption (Sit Less) and a walking PA intervention (Move More), as well as 1 control (no messages). Participants can select “Switch Off” messages for a certain amount of time in a particular day. Notification messages will be contextually adapted (based on location, weather and time of day), and delivered at 5 times throughout a day (see “decision points or times” section). Messages to interrupt SB will encourage participants to stand up and move. PA messages will aim to increase walking by 2 to 6 minutes. At each decision point, participants will be randomized only if they are available, meaning that they are not driving, not sleeping, not already active, and they are connected to the Internet. GPS will assist with recognition of driving if the user is on the move. A pre-set time (8:30 p.m. to 8:00 a.m.) will be considered for rest and sleeping. In addition, sleeping can be manually modified by user. Decision points (times): Five decision points, from 8:00 a.m. to 8:30 p.m., will be selected as follows: morning, lunchtime, afternoon, late afternoon, evening Participants, who are available, will be randomized to receive (Sit Less/ Move More) intervention or not to receive it (control) at each decision points. Sample Size: A total of 22 adults with type 2 diabetes (T2D) will be invited. A total of 22 participants was estimated to detect a small proximal treatment effect size (ES) of 0.13, with 80% power, at the level of 5% statistical significance. This is based on the assumptions of 5 decision points per day, constant randomization probability of 0.7, and expected participant availability of 70%.