Physical Activity and Social Comparison: The Importance of Group Composition in an Employee Fitbit Intervention.

This study investigated how group composition influences changes in daily physical activity, measured by steps, during a 6-week Fitbit-based intervention among university employees. Participants were categorized as low, medium, or high steppers based on baseline activity and assigned to homogeneous or heterogeneous groups, with some engaging in optional group step challenges featuring leaderboards for social comparison. Results showed that low steppers, particularly those in groups combining low and high steppers, exhibited the greatest increases in steps, especially at the intervention midpoint, while overall group composition effects were more pronounced among participants actively involved in group challenges. The findings highlight the role of group dynamics and social comparison in physical activity interventions using gamification, suggesting that intentional group design and participant engagement are important for optimizing behavior change outcomes.