When Workout Buddies Are Virtual: AI Agents and Human Peers in a Longitudinal Physical Activity Study

TL;DR

This six-month study compares human, AI, and solo exercise partners, revealing AI peers offer consistent support while human peers evoke stronger social presence, informing future hybrid health interventions.

Contribution

The study provides empirical evidence on long-term effects of AI versus human exercise partners, highlighting their complementary roles in motivation and support.

Findings

AI peers offer more consistent encouragement.

Human peers evoke stronger social presence.

Hybrid approaches may optimize motivation.

Abstract

Physical inactivity remains a critical global health issue, yet scalable strategies for sustained motivation are scarce. Conversational agents designed as simulated exercising peers (SEPs) represent a promising alternative, but their long-term impact is unclear. We report a six-month randomized controlled trial (N=280) comparing individuals exercising alone, with a human peer, or with a large language model-driven SEP. Results revealed a partnership paradox: human peers evoked stronger social presence, while AI peers provided steadier encouragement and more reliable working alliances. Humans motivated through authentic comparison and accountability, whereas AI peers fostered consistent, low-stakes support. These complementary strengths suggest that AI agents should not mimic human authenticity but augment it with reliability. Our findings advance human-agent interaction research and point to hybrid designs where human presence and AI consistency jointly sustain physical activity.