Effects of Just-in-time Adaptive Interventions on Physical Activity in Romantic Couples: A Micro-randomised Trial

In this study, we investigate the effects of just-in-time adaptive interventions (JITAIs) on moderate-to-vigorous physical activity (MVPA) in romantic couples. These JITAIs aim to enhance the social exchange processes (i.e., social support and social control) that are assumed to facilitate physical activity. We explore the effectiveness of different types of JITAIs. To do this, we categorize the JITAIs according to the continuum of dyadic interventions proposed by Scholz et al. (2020) in cross-over and joint interventions. Furthermore, we distinguish different time points when the participants receive the JITAIs (i.e., before the planning, before the activity, and during evaluation) targeting the physical activity at different time points. Finally, we explore if the different types of interventions vary in their longer-term effects.