Designing Group Activity Metrics for Social Interaction and Walking Adherence: A Social Prototyping Study Among Indian Older Adults.

Adherence to physical activity is critical for healthy ageing, yet older adults often struggle to maintain consistent routines. We introduce Group Activity Metrics (GAMs), a design construct comprising group visualisations shared within familiar, small social groups, and examine how they facilitate social interaction and support walking adherence among Indian older adults. Guided by Social Cognitive Theory (SCT) and informed by interviews and focus groups with 22 participants, we designed GAMs and deployed them in two walking cohorts. We evaluated them through social prototyping, an approach that captures early-stage social responses to design ideas. Our findings show that GAMs sparked curiosity and enabled social interaction, suggesting potential to support walking adherence. This work contributes empirical insights into the role of small-group social interaction in walking adherence, introduces GAMs as a theory-informed design construct, and positions social prototyping as a methodological approach for evaluating socially driven technologies in HCI.