Original researchSchool's out … now what? Objective estimates of afterschool sedentary time and physical activity from childhood to adolescence

ObjectivesTo describe the change in afterschool levels of sedentary time and physical activity from childhood to adolescence.DesignLongitudinal.Methods375 youth (50% boys) from the Study of Early Child Care and Youth Development (United States) provided accelerometer data at 9 (2000/01) and 15 yrs (2006/07). Average time spent in sedentary, light, moderate, vigorous, and moderate-to-vigorous physical activity (MVPA; min h−1) was reported across the afterschool period (15:00-22:00) and separately across whole days. Mean comparisons were conducted to report between- and within-group differences in afterschool data. Analysis of covariance was used to determine the effect of sex, ethnicity, and baseline body mass index (BMI) on the 6-yr change in afterschool sedentary time and MVPA before and after adjusting for covariates (baseline afterschool sedentary/MVPA time, change in non-afterschool sedentary/MVPA time, difference in afterschool wear time, and socioeconomic status).ResultsFrom 9 to 15 yrs, sedentary time increased and activity decreased during the afterschool period. After covariate adjustment, the decline in afterschool MVPA was significantly greater among girls, compared to boys (B coefficient (95%CI) = −0.94 (−1.47, −0.40)), and among overweight/obese youth, compared to youth with normal BMI values (B coefficient (95%CI) = −0.65 (−1.22, −0.08)).ConclusionsDuring the transition from childhood to adolescence, afterschool activity (min h−1) decreases while sedentary time increases. Programs are needed throughout this period that promote the maintenance of activity or encourage additional activity with age.