Promoting leisure-time physical activity through a school-based family-centred approach: methodology and co-creation process of the ‘PHASE family’ intervention

The design and methodology of ‘PHASE family’, a family-centred intervention that repurposed underused school facilities after school hours to promote leisure-time physical activity, are described. The intervention followed a 20-week pragmatic controlled trial design and involved 265 participants across 13 schools in five European countries. A systematic review and pre-intervention focus groups informed a semi-structured protocol, while attendance and post-intervention focus groups documented implementation. Parents and children valued shared participation and supported continuing the initiative, although scheduling constrained involvement. This feedback highlights the relevance of participant involvement in the co-creation of physical activity initiatives.