Objective: To model changes in body mass index (BMI), including its stability, and to investigate the association between physical activity, 1-mile run/walk and levels of gross motor coordination and BMI during 5 consecutive years.
Design: A longitudinal study of children 6 years of age at baseline followed at annual intervals over 5 years.
Subjects: A total of 285 children (143 boys and 142 girls) were enrolled in grade 1 (age 6 years) and followed through grade 5 (age 10 years).
Measurements: BMI was recorded and physical activity was assessed by questionnaire, aerobic fitness was evaluated with the 1-mile run/walk and gross motor coordination was measured with the KTK test battery (Körperkoordination test für Kinder). Multilevel modelling techniques were for the primary analysis.
Results: Changes in BMI showed similar curvilinear trends in boys and girls, with ample inter-individual crossing trajectories that is, low tracking. Longitudinal changes in physical activity (PA) and aerobic fitness were not significantly associated with BMI-changes during the 5 years. Children who were more proficient in their motor coordination showed lower values of BMI during the 5 years.
Conclusions: BMI trajectories of both boys and girls show low tracking of BMI-values. Considerable inter-individual variation exists both in baseline BMI-values and changes (velocity and acceleration) over time. PA and fitness were not associated with BMI-changes, but gross motor function was negatively associated with BMI-changes. No gender-specific associations were found. If confirmed in other populations these observations could be translated in the promotion of physical activities that improve gross motor function in children aged 6-10 years. This seems to be of major importance for the physical education curriculum of primary school children.