Variation in Physical Activity Lies with the Child, Not the Environment: Evidence for an ‘Activitystat’ in Children (The EarlyBird Diabetes Study)

Introduction There is much interest in children’s physical activity (PA), but little understanding of its control. The evidence that total activity levels could be increased by the provision of greater opportunity for physical activity is lacking.

Methods and Participants MTI-Actigraph accelerometers recorded weekly PA in two groups of healthy children: Group 1: 215 9-year-olds from three schools (S) differing widely in timetabled physical education (PE) (S1 = 9.0 h/week, S2 = 2.2 and S3 = 1.8). Group 2: 300 of the EarlyBird cohort examined at age 5 years and again at age 6 years.

Results Group 1 – In-school PA was predictably higher in S1 (B: S1 = 18.6, S2 = 12.5, S3 = 11.0, G: S1 = 16.9, S2 = 9.7, S3 = 11.4 PA units/wk, P < 0.001), but PA lacking in S2 and S3 was made up out of school (B: S1 = 16.1, S2 = 26.6, S3 = 22.8, G: S1 = 13.6, S2 = 22.7, S3 = 22.6 PA units/wk, P < 0.001). Indeed, only 1% of the variance in weekly PA could be explained by the five-fold difference in timetabled PE. Group 2 – The PA loss by car transport to school (walk 4.9, car 4.2 PA units/wk, P < 0.001) was ‘recovered’ by after-school PA (walk 9.1, car 9.8 PA units/wk, P = 0.08). Total weekly PA was identical (walk 37.6, car 37.6 PA units/wk, P = 0.97). Weekday/weekend day and year-on-year correlations were high for both genders (r = 0.43–0.56, P < 0.001).

Conclusions These findings suggest that, despite widely differing opportunity, the variation in PA lies mostly with the child, and not his/her environment, and that PA is under central/biological control – an ‘activitystat’. This may have important implications for future interventions designed to increase children’s PA levels.