Evaluating implementation fidelity of a school-based physical education intervention: effects on child physical activity

Several school-based physical activity interventions have been developed to address the critical public health concern that children are not meeting the recommended daily moderate-to-vigorous physical activity (MVPA). However, less is known about implementation fidelity and its impact on programme efficacy. This study examined process evaluation findings of a school-based physical education (PE) intervention and its impact on MVPA among 3rd and 4th-grade children. Four fidelity components (adherence, dose, quality of delivery, and participant responsiveness) were assessed through weekly, unannounced direct observations of intervention classrooms. MVPA was assessed using accelerometry at baseline and post-intervention. Multilevel modelling was used to assess the effect of implementation fidelity on child MVPA. Overall fidelity score of our intervention was high (76.4%), although participant responsiveness (82.4%) and quality of delivery (77.8%) were implemented more successfully than dose (65.8%) and adherence (52%). Participant responsiveness was a statistically significant predictor of change in student MVPA (β = 26.14, 95% CI: 2.68, 49.60). Adherence, dose, quality of delivery, and overall fidelity were not significant predictors of student outcomes. Participant responsiveness is an important aspect of fidelity. School-based PE interventions should focus on enhancing student engagement for successful impact. Further investigation is needed to identify factors that enhance child responsiveness.