Reducing Sedentary Behaviour in Office Workers With a HAPA mHealth Intervention and a Just In-Time Adaptive Intervention

This study will explore the effectiveness of two different interventions, a Health Action Process Approach (HAPA) mobile health (mHealth) intervention and a Just In-Time Adaptive Intervention (JITAI), on reducing sedentary behaviour in office workers. One third of participants will receive the mHealth HAPA intervention, consisting of a theory-driven behavioural counselling session with personalized daily SMS text messages, and another third of participants will receive the JITAI intervention, a behaviour tracking mobile phone application that will alert participants once a set sedentary behaviour condition has been met. The last third of participants will act as a control where they will not receive an intervention or any further information from the letter of information. The study will take place over four weeks, with the first acting as a baseline and the intervention period filling the latter three weeks.