PURPOSE To establish physical activity (PA) intensity cutpoints for a wrist-mounted GeneActiv accelerometer (ACC) in elementary school-aged children. A second purpose was to apply cutpoints to a free-living sample and examine duration of PA based on continuous 1s epochs. METHODS Metabolic and ACC data were collected during nine typical activities in 24 children ages 6–11. Measured VO2 values were divided by Schofield-estimated resting values to determine METs. ACC data were collected at 75 Hz, band pass filtered and averaged over each one-second interval. Receiver Operator Characteristic (ROC) curves were used to establish cutpoints at <1.5, 1.5–3, 3–6 and ≥6 METs for sedentary, light, moderate and vigorous activity, respectively. These cutpoints were applied to a free-living independent data set to quantify the amount of moderate-vigorous PA (MVPA) and to examine how bout length (1, 2, 3, 5, 10, 15 and 60 seconds) affected the accumulation of MVPA. RESULTS ROC yielded areas under the curve of 0.956, 0.946 and 0.940 for sedentary, moderate and vigorous intensities, respectively. Cutpoints for sedentary, moderate and vigorous intensities were 0.190, 0.314 and 0.998 g, respectively. Intensity classification accuracies ranged from 27.6% (light) to 88.7% (vigorous) when cutpoints were applied to the calibration data. When applied to free-living data (n=47 children ages 6–11), estimated daily MVPA was 308 minutes and decreased to 14.3 minutes when only including 1 min periods of continuous MVPA. CONCLUSION Cutpoints that quantify movements associated with moderate-vigorous intensity, when applied to a laboratory protocol, result in large amounts of accumulated MVPA using the 1s epoch compared to prior studies, highlighting the need for representative calibration activities and free-living validation of cutpoints and epoch length selection.

Because few public elementary schools in the United States provide daily physical education or its equivalent for all students throughout the school year, noncurriculum approaches to increasing children's physical activity are important. Renovated schoolyards increase the number of children who are physically active, as well as their overall activity levels, and reduce sedentary behaviors.

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BackgroundChildren in poor and minority neighborhoods often lack adequate environmental support for healthy physical development and community interventions designed to improve physical activity resources serve as an important approach to addressing obesity. In Denver, the Learning Landscapes (LL) program has constructed over 98 culturally-tailored schoolyard play spaces at elementary schools with the goal to encourage utilization of play spaces and physical activity. In spite of enthusiasm about such projects to improve urban environments, little work has evaluated their impact or success in achieving their stated objectives. This study evaluates the impacts of LL construction and recency of renovation on schoolyard utilization and the physical activity rates of children, both during and outside of school, using an observational study design.MethodsThis study employs a quantitative method for evaluating levels of physical activity of individuals and associated environmental characteristics in play and leisure environments. Schools were selected on the basis of their participation in the LL program, the recency of schoolyard renovation, the size of the school, and the social and demographic characteristics of the school population. Activity in the schoolyards was measured using the System for Observing Play and Leisure Activity (SOPLAY), a validated quantitative method for evaluating levels of physical activity of individuals in play and leisure environments. Trained observers collected measurements before school, during school recess, after school, and on weekends. Overall utilization (the total number of children observed on the grounds) and the rate of activity (the percentage of children observed who were physically active) were analyzed. Observations were compared using t-tests and the data were stratified by gender for further analysis. In order to assess the impacts of LL renovation, recently-constructed LL schoolyards were compared to LL schoolyards with older construction, as well as un-renovated schoolyards.ResultsOverall utilization was significantly higher at LL schools than at un-renovated schools for most observation periods. Notably, LL renovation had no impact on girl's utilization on the weekends, although differences were observed for all other periods. There were no differences in rates of activity for any comparison. With the exception of the number of boys observed, there was no statistically significant difference in activity when recently-constructed LL schools are compared to LL schools with older construction dates and there was no difference observed in comparisons of older LL with unrenovated sites.ConclusionsWhile we observed greater utilization and physical activity in schools with LL, the impact of specific features of LL renovation is not clear. However, schoolyard renovation and programs to encourage schoolyard use before and after school may offer a means to encourage greater physical activity among children, and girls in particular. Additional study of schoolyard renovation may s...