Health behaviour change: Theories, progress, and recommendations for the next generation of physical activity research.

Adaptive behaviour change is central to improving population health, yet poor adoption of health-enhancing behaviours contributes to noncommunicable diseases and so remains a global concern. Research on physical activity behaviour change has continued to expand and evolve since the turn of the millennium, guided by diverse theoretical approaches-from social cognitive theories, organismic dialectical approaches such as Self-Determination Theory, dual-process frameworks, and integrated practical models and taxonomies. Key challenges and opportunities remain, however, and in this paper we offer several calls to action for those working to advance physical activity behaviour change theory, research, and practice. First, we advocate for more precise examination of behaviour change itself, moving beyond static models to incorporate dynamic theories and methodologies (including data analysis) that better capture how behaviours evolve and change over time. Second, we emphasise the need to prioritise behaviour maintenance, recognising that many interventions succeed in initiating change but fail to support long-term adherence. Third, we call for a concerted effort to broaden our target populations in behaviour change research, ensuring that interventions (and the theories that inform them) are more inclusive, widely applicable, contextually relevant, and equitable. Finally, we highlight the growing recognition of automatic processes in shaping physical activity behaviours and outline the importance of refining measurement tools and intervention strategies to account for these non-conscious influences. These considerations are articulated with a view to supporting the next generation of physical activity behaviour change research and practice, and in doing so contribute to improved population health equity and outcomes.