Degree of implementation of a play-based curricular intervention affects children's movement in afterschool settings.

Programs implemented in afterschool settings can support children's health; however, their effectiveness may depend on the degree of implementation which can vary by school. In this cluster-randomized controlled trial, we assessed the effect of a play-based curricular intervention on physical activity (PA) levels among children (N=133) attending seven intervention and seven comparison afterschool programs in Arizona (U.S.) using general linear mixed models, and examined how degree of intervention implementation impacted children's PA using linear regression models. PA was measured using wrist-worn accelerometers and degree of implementation was measured using a researcher-developed 100-point index with data from surveys and training attendance from each school. After the intervention, children receiving the curriculum increased their light PA by 4.7 minutes and decreased their sedentary time by an average of 10.2 minutes daily. When degree of implementation was considered, we found variability between schools in children's sedentary time and moderate-to-vigorous PA (MVPA) after the intervention. Based on the average time spent in the afterschool programs daily (2.9 hours), children averaged 5.2 more MVPA minutes and 7.0 less sedentary minutes for every 10-point increase in implementation index score. Considering the 30-point variability in scores between schools, this translated to children spending up to 16 minutes more in MVPA and 21 minutes less being sedentary of the average 2.9 hours spent in afterschool programs with the highest level of implementation compared to the lowest. Degree of implementation matters when integrating curricula in afterschool settings that target children's movement. Stronger implementation may reduce children's sedentary behavior and increase MVPA.