The purpose of this study was to examine the between-day reproducibility of physical activity across 1 week and determine the stability of physical activity over 2 years. Forty-two children (19 boys, 23 girls) aged 8–9 years at the beginning of the study were followed across 1 week and over a 2-year period. Physical activity was assessed by Caltrac accelerometer. Reproducibility and stability of physical activity was analyzed using Spearman correlations. The results revealed significant Spearman rank order correlations between weekdays (r = 0.64 to 0.79) and weekend days (r = 0.53 to 0.67). Spearman rank order correlations between weekdays and weekend days during two monitoring sessions were consistently lower, ranging from 0.34 to 0.57. It was concluded that the between-day reproducibility of accelerometer monitoring was higher between similar days of the week (weekdays or weekend days). Shortterm stability of physical activity during late childhood was moderate.
The Authors are with the Institute of Sport Pedagogy at the University of Tartu, Tartu, EE 2400 Estonia.