The measurement of physical activity in young children.

Two studies were conducted to determine the validity of various measures of physical activity in young children. In Study 1, 21 preschool children were utilized to explore how well measures of children's activity obtained from parents, teachers, and the children predicted observed behavior at school and in the home. Study 2 (n = 51 preschool children) focused on the predictive validity of the Caltrac motion sensor. In both studies, detailed minute-by-minute ratings of children's activity in Study 1 were generally ineffective in predicting observed physical activity. Children's activity preferences, however, were significantly related to the proportion of high intensity physical activity performed. In Study 2, there was a significant relationship (r = .86, p less than .0001) between Caltrac readings and observed physical activity. This correlation was similar for boys and girls, normal and overweight children, and younger and older children. These findings suggest that the Caltrac monitor may provide a valid index of individual differences in physical activity in young children.