Abstract
INTRODUCTION: Physical activity is crucial for young children's health and development. Many young children do not meet the recommended 3 hours of daily physical activity, including 60 min of energetic play. Early childhood education and care (ECEC/childcare) is a key setting to intervene to improve children's physical activity. The Play Active programme is a scalable evidence-informed ECEC-specific physical activity policy intervention with implementation support strategies to improve educators' physical activity-related practices. METHODS AND ANALYSIS: This hybrid type III effectiveness-implementation trial will use a quasi-experimental repeated measures design to assess the real-world effectiveness of Play Active's scalable implementation support strategies in helping ECEC services adopt the practices included in the Play Active policy. Secondary aims will examine changes in educator-reported and device-measured children's physical activity; assess the sustainability of the programme; identify effective dissemination strategies; assess cost-effectiveness; and involve comprehensive process evaluation. All ECEC services in Western Australia (n=776), Queensland (n=1744) and South Australia (n=445) will be invited to participate. Data will be collected at baseline, 6, 12, 18, 24 and 30 months. ETHICS AND DISSEMINATION: Ethics approval has been provided by The University of Western Australia Human Research Ethics Committee (HREC) (2023/ET000187), the University of Queensland HREC (2024/HE000076) and the University of South Australia HREC (206023). This real-world trial of Play Active is vital for understanding its implementation in practice and to generate evidence for further scale-up and roll-out nationally. Key findings will be disseminated to stakeholders, collaborators, policy-makers as well as families and practitioners in the ECEC sector. TRIAL REGISTRATION NUMBER: ACTRN12624000406505.