Impact of a multi-level, multi-component intervention to improve elementary school physical education on student cardiorespiratory fitness: an application of the parametric g-formula.

Background: School physical education is an important population-level health intervention for improving youth fitness. The purpose of this study is to determine the causal impact of New York City's PE Works program on student cardiorespiratory fitness. Methods: This longitudinal study (2014-2019) includes 581 elementary schools (n=315,999 4 th /5 th -grade students; 84% non-white; 74% who qualify for free or reduced-price meals). We apply the parametric g-formula to address schools' time-varying exposure to intervention components and time-varying confounding. Results: After four years of staggered PE Works implementation, 49.7% of students per school (95% CI: 42.6%, 54.2%) met age/sex-specific cardiorespiratory fitness standards. Had PE Works not been implemented, we estimate 45.7% (95% CI: 36.9%, 52.1%) would have met fitness standards. Had PE Works been fully implemented in all schools from the program's inception, we estimate 57.4% (95% CI: 49.1%, 63.3%) would have met fitness standards. Adding a PE teacher, alone, had the largest impact (6.4% (95% CI: 1.0, 12.0) increase). Conclusion: PE Works, which included providing PE teachers, training for classroom teachers, and administrative/teacher support for PE, positively impacted student cardiorespiratory health. Mandating and funding multilevel, multicomponent PE programs is an important public health intervention to increase children's cardiorespiratory fitness.