Introduction
Physical activity (PA) interventions in schools can improve children’s overall PA levels and positively affect academic performance. However, implementing PA during the school day can be challenging in the complex school setting. Many school-based PA studies do not present their interventions’ design processes, although this knowledge is important to replicate the intervention.

Purpose
This article aims to provide insights into the collaborative design process of the two PA interventions for third-grade pupils of the ACTIVE SCHOOL project. The evidence-based interventions focus on PA integrated into academic content (Move & Learn intervention) as embodied learning or PA as moderate to vigorous activity performed during the school day (Run, Jump & Fun intervention). The study’s objective was to engage teachers and pedagogues early in the design process to ensure the design was tailored to practice.

Methods
A team consisting of researchers, school staff, and experts were involved in the design process. The process lasted one school year and comprised three phases: exploration and analysis, construction and design, and reflection and evaluation. Multiple methods were used, including focus group interviews, a design workshop, and observations of iterative in-school testing.

Results
The result of the analysis and exploration phase was a set of learning points based on information about school culture, school staff competences, and needs. The design and construction phase produced a set of intervention skeletons, which were the actual elements of the interventions. The evaluation and reflection phase created the main results, which are specific principles and multifaceted implementation strategies for Move & Learn and Run, Jump & Fun, respectively. Finally, dose and timing of the interventions were specified.

Conclusion
Collaboration with schools and an iterative approach were determinants for designing interventions appropriate to the Danish school context and school staff practice.