Assessing within- and between-day compensation of children's sitting and physical activity time using activPAL

Abstract

PURPOSE: The ‘activitystat’ hypothesis suggests that children compensate for increased physical activity at one time point by reducing their physical activity at another time point to maintain an overall activity set-point. However, compensatory changes across the physical activity spectrum (from sitting through to standing and stepping) have rarely been considered. This observational study examined whether compensatory changes in children’s postural positions occur within- and between-days. METHODS: Children aged 8-11 years from 8 primary schools located in Melbourne, Australia, wore an activPALTM (PAL Technologies Ltd, Glasgow) for 7 consecutive days (n=235). Sitting, standing and stepping time were derived for each day and for specific periods on weekdays and weekend days. Multilevel analyses were conducted using generalized linear latent and mixed models to estimate associations between temporally adjacent values (i.e. pairs of days; pairs of periods within-days) between the outcome variables. RESULTS: Significant associations were observed between temporally adjacent days and periods of the day. On any given day, an additional 10 minutes of stepping was associated with fewer minutes of stepping (~9 minutes; p<0.001) and standing (15 minutes; p<0.001) the following day. Greater time spent sitting during one period, regardless of being a weekday or weekend day, was associated with less time sitting and more time standing and stepping in the following period. CONCLUSIONS: The results were consistent with the ‘activitystat’ hypothesis. Children appeared to compensate for increased sitting, standing, and stepping time both within- and between-days. The implications of short-term compensatory changes on the design and delivery of interventions that aim to increase children’s physical activity levels require consideration