This is the first research methods book on the application of using a co-production approach for physical activity for health research. When used for research, co-production has potential to be hugely impactful. The underpinning ethos of co-production is to involve multiple and varied stakeholders throughout the process. This book offers evidence-based guidance, case studies, and reflections on using co-production specifically for physical activity and health research. By involving users at every stage, from conception to finalization of outputs, the book demonstrates the power of co-production as a tool for positive change across society, providing insights into understanding user needs, addressing barriers, developing meaningful outputs, and enhancing policy implementation. This book not only captures the current state of co-production within the field, but also lays the groundwork for future developments. The book offers insights into best practices, evidence-based approaches, and strategies to rectify any deviations from the intended co-production process. By exploring the 'what next' for the field, the authors encourage ongoing innovation and advancement in co-production methodology, and by involving a wide range of stakeholders in research, it provides a bridge between academics and non-academics. With its comprehensive coverage of co-production, physical activity for health, and the intersection between the two, this book provides a vital resource for researchers in qualitative research, physical activity, healthcare, intervention design and development, and wellbeing. It is also vital reading for practitioners and policymakers seeking to harness the potential of co-production to drive positive change in promoting physical activity and improving health outcomes for individuals and society at large.