Effects of an After-School Physical Activity Intervention on Physical Activity, Aerobic Fitness, and Body Composition

Abstract

Low levels of physical activity have been linked to the increased prevalence of obesity in children and adolescents. Federal and local policies to increase the focus on academic time have resulted in decreased physical activity time, such as physical education and recess, during the school day. Therefore, to help children and adolescents meet daily physical activity recommendations, it may be more feasible to change how children use their time outside of school than how they spend time during the school day. Purpose: The purpose of this study was to examine the effects of a 10-week after-school physical activity program on physical activity, aerobic fitness, and body composition in 5 to 12 year old participants. Methods: Participants (n = 277) from 15 after-school programs were assigned to an intervention group or a control group. After-school leaders were trained to lead participants in physical activities called After-School Energizers. After-School Energizers are physical activities designed to promote character development, leadership skills, and academic enrichment. After-school leaders were asked to record the activity they led each day on a tracking chart. Participants were assessed at baseline and follow-up on physical activity, body composition, and aerobic fitness. Physical activity was measured during after-school hours with pedometers (n = 277) and accelerometers (n = 112) for five days at baseline and for five days during the intervention. Body composition was assessed with body mass index (BMI), BMI percentile, and percent fat. Aerobic fitness was measured with the PACER 20-meter multistage shuttle run. Results: Participants accumulated a daily average of 3,497 (± 2,627) steps and 28.3 (± 13.6) minutes of MVPA at the after-school program. Approximately 60% of participants met the recommended level of physical activity for after-school programs. Results from a repeated measures analysis of variance (ANOVA) and effect size estimates indicated that percent fat was not substantially impacted by the intervention. Nonsignificant (p > .05) time x group interactions and small effect sizes indicated that the intervention did not impact BMI or BMI percentile. For aerobic fitness, no significant main effects or interactions were found (p > .05), indicating that the intervention had no impact on aerobic fitness. The analysis of physical activity assessed on the entire sample via pedometer demonstrated a significant (p < .001) time x group interaction, indicating that physical activity changed differentially for the intervention and control groups during the study. Physical activity levels for the intervention group stayed fairly constant from baseline to follow-up. In contrast, physical activity levels for the control group decreased by over 800 steps during the after-school program. Accelerometer-derived results demonstrated that both the intervention group (ES = 0.41) and control group (ES = 0.36) demonstrated a low to moderate increase in light physical activity time. Both intervention (ES = 0.31) and control (ES = 0.23) groups showed a small to moderate increase in moderate physical activity time. No increase in vigorous physical activity was seen in the intervention group (ES = 0.00) and a small increase was seen in the control group (ES = 0.13). Repeated measures ANOVA results demonstrated no significant effects (p > .05) for moderate-to-vigorous physical activity. Conclusion: The after-school physical activity intervention did not result in improvements, relative to the control group, in physical activity level, aerobic fitness, or body composition. It is possible that after-school leaders chose to implement the physical activities used in this intervention during times when participants would have already been physically active (e.g., during gym time or playground time). Consideration should be given to instruction on when such activities might have the largest impact, such as during more sedentary times. We documented that many children do not obtain the recommended level of physical activity during after-school programs. Future interventions should consider steps to increase implementation of physical activity opportunities in after-school programs.