Potential moderators of day-to-day variability in children's physical activity patterns.

Little is known about whether physical activity compensation occurs and, if so, what are potential moderators of such responses. This study examined whether children's physical activity, sedentary time and energy expenditure on one day was associated with these behaviours the following day, and what factors may moderate observed associations. One hundred and twenty-seven children (8-11 years) wore an ActiGraph accelerometer for eight days. Time spent in sedentary time and physical activity was obtained. Daily energy expenditure was also assessed using a SenseWear Armband (n=98). Moderators examined were sex, age, BMI, fitness, and fundamental movement skills (FMS). Multilevel analyses were conducted using generalized mixed models. On any given day, every additional 10 minutes spent in moderate-to-vigorous physical activity (MVPA) was associated with 9.3 minutes less MVPA the following day. Every additional 10kcal expended on one day was associated with 2.9 fewer kcal expended the following day. Additional time spent sedentary on any given day was associated with less light physical activity the following day in children with lower FMS. The results are largely consistent with the compensation hypothesis, with children appearing to compensate their activity between days. Strategies to minimise potential compensatory changes may be needed for children overall rather than for specific population sub-groups.