Longitudinal Change in Physical Activity in Children 6 to 36 Months of Age.

Objective: To describe the developmental pattern for physical activity (PA) in children 6-36 months of age and to identify factors that are longitudinally associated with PA as children transition from infancy to preschool age.

Study Design: The study employed a prospective longitudinal design with baseline data collected when children were approximately 6 months of age. Mothers and infants (n = 124) were recruited through community and educational settings in South Carolina. Data were collected at 6-month intervals from 6 to 36 months. PA was measured via accelerometry. Mothers completed questionnaires that assessed independent variables, including parent characteristics, the child's sex, race, and ethnicity, birth/delivery type, motor milestones, sleep habits, dietary practices, childcare setting, and home environmental factors. Trained research staff administered anthropometric measures and assessed motor developmental status. Growth curve models described the age-related pattern for PA and evaluated relationships between independent variables and change in PA.

Results: PA increased by approximately 45% between 6 and 36 months of age and followed a curvilinear pattern, with most of the increase occurring between 6 and 24 months. The child's exposure to television/electronic media was negatively associated with change in PA, and the presence of older siblings in the home was positively associated with change in PA.

Conclusions: As children develop from infancy to early childhood, their PA increases substantially, with most of the increase occurring by 24 months of age.