Designing a context-specific intervention in practice: learning from a school-based physical activity intervention.

Background: Public health interventions need to be designed for the intervention setting. Traditionally, to maximise internal validity, school-based pupil physical activity interventions deliver an identical programme across all settings. However, an interventions' success will depend on the context in which it is implemented, i.e. a schools' social, cultural, economic, environmental and other characteristics. In this paper we use the development of the PASSPORT (Physical Activity via a School-Specific PORTfolio) intervention as a case study for the development of context-specific public health interventions. We outline how we developed the intervention and draw out key learning from this for public health interventions generally. Methods: The PASSPORT intervention takes a portfolio approach that allows schools to select and deliver tailored intervention content that is most suitable to their setting. The intervention was developed across multiple research steps that were designed to progressively build knowledge on school context and physical activity and integrate these into intervention design. We outline these in the paper. Formative studies include: a scoping review of intervention components; school staff interviews; a rapid ethnography; and a school survey. These findings informed the co-design of the intervention tool with primary school staff and the development of the portfolio content. Finally, we conducted a pilot study in two schools to learn from both the delivery of the intervention and associated evaluation data collection. Key learning: Key learning for context-specific intervention design has been gathered around four areas: Ground intervention design in a range of data and insight, Centre contextual experience, Design for intervention flexibility and user autonomy, and, Build in processes to test and iterate. Conclusions: Each of the formative studies and the intervention design steps provided parts of the complex picture of intervention context and design needs. Combined, the results of the studies supported the development of a context-specific intervention.