Participants were recruited from 40 primary schools selected by location and the Index of Multiple Deprivation (IMD) score (a
government-produced area level measure of deprivation) for each school postcode. The final sample approximately click here reflected IMD tertiles of all state schools within a 15-mile radius of the University of Bristol, with twelve, sixteen and twelve schools respectively from high, middle and low IMD tertiles. In total, 1684 Year 6 children were invited to take part in the study and 986 children provided data (a response rate of 58.6%). Informed parental consent was obtained. The study was approved by a University of Bristol ethics committee. Physical activity was assessed using ActiGraph GT1M accelerometers (ActiGraph, LLC, Pensacola, FL). A 10-s epoch was used to capture the intermittent nature of children’s physical activity. Consistent with previous studies, data were collected for 5 continuous days, including 2 weekend days. Participants were included in the analyses if they provided ≥ 500 min of data for at least 3 days (n = 747) ( Steele et al., 2009). Mean activity levels (CPM) and minutes of moderate to vigorous intensity physical
activity per day (MVPA), which is regarded as “health-enhancing” (Department of Health, 2004), were calculated. Both measures were averaged across the whole day and for the after school period (3 pm–6 pm) on weekdays, across Olopatadine both selleck inhibitor weekend days and across the whole week. Leisure-time physical activity was defined as the period from 3 pm until
6 pm on weekdays and all day at weekends. Physical activity that resulted in ≥ 3200 CPM was treated as MVPA (Puyau et al., 2002). While acknowledging the considerable debate over cut-points, we opted for 3200 because it was obtained from highly robust laboratory calorimetry (Puyau et al., 2002). However, given that there is a 9% difference in values between the GT1M monitors and the 7164 monitors, (Corder et al., 2007), a correction factor of 0.91 was used to give a cut-point of 2912 counts per minute. Contextual information regarding children’s physical activity was provided by children’s self-reported active play. A single question asked: “How often do you play with your friends or family outside near your home?” Response categories were “Never,” “1–2 days per week,” “3–4 days per week” and “5 or more days per week.” A pilot test of the reliability of this question with 47 Year 6 children produced a test-retest correlation of 0.72 and an alpha of 0.84, indicating good reliability. For regression analysis the four categories were converted to indicator variables with “Never” as the reference category. Body mass index (kg/m2) was converted to an age and gender specific standard deviation score (BMI SDS) (Cole et al., 1995). IMD was derived from household postcode.