Implementation at-scale of school-based physical activity interventions: A systematic review utilizing the RE-AIM framework.

School-based interventions can increase young people's physical activity levels, but few are implemented at-scale (i.e., the expanded delivery of efficacious interventions under real-world conditions into new/broader populations). The Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework can be used to describe the extent to which interventions have been implemented at-scale. The aim of our review was to determine the extent to which studies of school-based physical activity interventions implemented at-scale reported information across the RE-AIM dimensions. We conducted a systematic search of seven electronic databases to identify studies published up to June 2019. A total of 26 articles (representing 14 individual studies) met the inclusion criteria and were analyzed. Eleven studies reported actual or estimated number of students exposed to the intervention; however, the representativeness of these students was rarely reported. Nine studies reported the intervention effect on the primary outcome during scale-up. Ten studies reported the rate of participating schools/teachers; however, none reported on the characteristics of adopters/nonadopters. Eight studies reported intervention fidelity. Eleven studies described the extent to which the intervention was sustained in schools. There was considerable variability in the reporting of RE-AIM outcomes across studies. There is a need for greater consistency in the evaluation, and reporting of, school-based physical activity interventions implemented at-scale.