CDC childhood physical activity strategies fail to show sustained fitness impact in middle school children

An increasing number of children are now obese and fail to meet minimum recommendations for physical activity (PA). Schools play a critical role in impacting children's activity behaviors, including PA. Our objective was to assess whether CDC-based school-centered strategies to promote PA increase long-term cardiovascular fitness (CVF) levels in students in schools. A prospective observational trial was conducted in 26 middle schools to implement CDC school-based strategies to increase PA for 3 years. Students had CVF assessed by Fitnessgram (PACER), a 20-meter shuttle run, at the start and end of each school year. A post-study questionnaire was administered to assess each school's strategy adherence. At baseline, 2402 students with a mean age 12.2 ± 1.1 years showed a mean CVF measured by PACER of 33.2 ± 19.0 laps (estimated VO₂max 44.3 ± 5.3 ml/kg/min). During the first year, there was a significant increase in the mean PACER score (Δ = 3, 95% CI: 2-4.1 laps, p < 0.001) and PACER z-score (Δ = 0.09, 95% CI: 0.04-0.14, p = 0.001). Subsequently, however, a significant negative trend in PACER z-scores occurred (β = -0.02, p < 0.0001) so that over the 3-year study period, the intervention did not increase overall CVF. This effort to implement CDC school-based PA strategies in middle schools did not result in sustained increase in CVF over 3 years. It remains to be clarified whether this limited efficacy indicates that CDC physical activity strategies are not sufficiently robust to meaningfully impact health outcomes and/or additional support is needed in schools to improve fidelity of implementation.