Day-dependent step-count patterns and their persistence over 3 years in 810-year-old children: The LOOK project

Background: Physical activity in children is known to be generally lower at weekends but whether systematic day-to-day differences exist throughout the week is unclear. Aim: To determine if weekly patterns of pedometer-assessed physical activity (PPA) exist in elementary school-aged Australian boys and girls and whether they persist over 3 years. Subjects and methods: Seven-day pedometer measurements were recorded from 389 boys and 387 girls of initial age 8.0 (SD 0.3) in three successive years during spring. General linear mixed modelling was used to investigate patterns and the persistence of PPA. Results: A pattern did emerge, significant differences in PPA occurring between certain days of the week (p<0.001). This pattern was similar in each year, PPA increasing from Monday through to Friday, decreasing on Saturday and again on Sunday. PPA was greater in boys (p<0.001), but less so on weekends. Significant day-to-day and year-to-year intra-class correlations of PPA (0.14 and 0.29, respectively, both p<0.001)) within individuals provided evidence of tracking on a daily basis, and to a lesser extent yearly. Conclusions: A well-defined week-long pattern of steps/day emerged in these 810-year-old children, the pattern being similar in three consecutive years.