Physical inactivity increases risks of cardiovascular disease, poor mental health, and morbidity. School-based physical activity (PA) promotion can reach children from differing backgrounds in a large proportion of their waking hours. Education outside the classroom (EOtC) is an PA-integrating pedagogical approach that aligns PA with the primary goals of schools and is therefore thought to present an acceptable, feasible, and efficacious model for school-based PA. This registered report used a cluster randomised wait list design to evaluate the efficacy of an EOtC intervention that aims to increase adolescents' (ages 10-16 years) school-based (school week) and overall (full week) PA by providing a course on the pedagogical and didactic methods of EOtC to teachers across 30 Danish schools, and subsequently the teachers implementing EOtC in their classes > 5 h weekly over the course of one school year. Across 20 schools, 503 pupils aged 9-14 years were enrolled. The intervention group classes delivered a weekly mean of 238 (± 50) minutes of EOtC per-protocol and engaged in 20.4% moderate-to-vigorous school-based PA above the control group, however with no effect on overall PA. Enhancing effectiveness on overall PA, supplementing the intervention with additional PA activities, or adjusting its delivery and implementation is necessary. Protocol registration The stage 1 protocol for this Registered Report was accepted in principle on 22/08/22. The protocol, as accepted by the journal, can be found at: h t t p s : / / d o i . o r g / 1 0 . 1 7 6 0 5 / O S F . I O / N T M 9 K .
AbbreviationsEMM Estimated marginal mean EOtC Education outside the classroom ITT Intention-to-treat LMM Linear Mixed Model LPA Light physical activity MVPA Moderate-to-vigorous physical activity PA Physical activity PP Per-protocol SD Standard deviation SED Sedentary physical activity Adequate levels of physical activity (PA) and sedentary time reduces risk of non-communicable diseases, such as diabetes 1 , and enhances mental health 2 . PA levels have declined over the past 22 years, especially in adolescents 3 . Indeed, a large proportion of adolescents, especially girls, are far from reaching the PA guidelines, and activity
