IMPROVE aims to conduct a hybrid type 3 evaluation design to test the effects of bundled implementation strategies on the intervention fidelity (primary outcome) of the Healthy School Start (HSS) program while simultaneously monitoring effects on health outcomes of children and parents (secondary outcomes). The HSS is a 4-component family support program for children starting school (5-7 years of age) promoting healthy dietary habits and physical activity in the home environment to prevent childhood obesity and parent risk of developing type 2 diabetes.~IMPROVE is a cluster-randomized controlled trial with two arms to evaluate and compare the effects of two different bundles of implementation strategies on intervention fidelity expressed as adherence and responsiveness at 12 and 24 months. Thirty schools in two municipalities will participate in the study reaching about 1400 families per school year. In stakeholder workshops, key implementation determinants were identified according to the domains of the Consolidated Framework for Implementation Research. Through a consensus process with stakeholders, two bundles of implementation strategies were tailored to address context-specific determinants. Schools randomly assigned to group 1 will receive bundle 1 (Basic) and group 2 will receive bundle 1+2 (Enhanced), consisting mainly of external facilitation, fidelity monitoring and feedback strategies. Secondary outcomes will include acceptability, appropriateness, feasibility, organisational readiness as perceived by school staff, child weight status and diet, and parents' risk of type 2 diabetes. Linear and ordinal regression analysis will be used to test the effect on the primary and secondary outcomes, taking clustering into consideration where needed. Process evaluation will be conducted through key stakeholder interviews to investigate experiences of the program and stakeholder perceptions on sustainability.~This systematic approach to investigating the effects of two different bundles of implementation strategies tailored to context-specific determinants on the fidelity of the HSS intervention will provide new insight into feasible implementation strategies and the external supports needed for a school-based health program like the HSS to be effective and sustainable. Results will help inform how to bridge the gap between the research on school-based health programs and routine practice in schools.
IMPROVE is an implementation study aiming to explore the effects of two bundled implementation strategies on the intervention fidelity of the Healthy School Start program (primary outcome) while simultaneously monitoring effects on health outcomes of children and parents (secondary outcomes). Thirty schools in two municipalities will receive the HSS program reaching about 1400 families per school year, for two years.