Background
An increasing share of workers have at least some autonomy in choosing their work times and locations. The COVID-19 pandemic further increased this number, which is expected to remain high. Flexible work designs (FWDs), such as flextime, telework, and mobile work, provide workers with temporal and spatial flexibility [Therefore, it is important to support workers in coping with these specific challenges of FWDs. Individual occupational web-based interventions can improve recovery, well-being, and work-life balance [However, we noticed that research tends to overlook the shortcomings of web-based interventions, such as high and easy dropout and feelings of isolation [This study contributes to the literature in several ways. First, there is little research comparing the effect of training formats in the work context, and past research that compared formats of occupational interventions has focused on comparing the effectiveness of face-to-face versus web-based interventions [Second, based on social identity theory and self-determination theory, we aimed to empirically test the theoretical assumption that group interactions increase commitment, social support, and thus training effectiveness. In doing so, we integrated research on blended learning, which is mainly discussed in education psychology, and occupational intervention research, which is mainly discussed in occupational psychology. In particular, we combined research on learning settings and occupational interventions with the theoretical frameworks of group interactions. Moreover, we contributed to the discussion on how to reduce attrition in web-based interventions [Third, we conducted this study as a randomized controlled trial with 4 measurement points, addressing the call for more randomized controlled trials on work-specific interventions [