Assessing daily physical activity in elementary school students used by accelerometer: A validation study against doubly labeled water method

The purpose of present study was to examine validity of accelerometer (Lifecorder; LC) and to assess the free-living physical activity (PA) in Japanese elementary school students used by LC method. Firstly, to examine validity of LC, twelve children, aged 11.2±1.0years, were measured total energy expenditure (TEE) by doubly labeled water method and resting energy expenditure (REE) by the expired gas analysis. Physical activity energy expenditure (PAEE) is calculated as 0.9 TEE minus REE. At the same time, PA was evaluated by both daily walk count (WC) and vigorous activity time (LC7-9) using LC method. PAEE per 1 kg body weight significantly correlated with WC (r = 0.785, p<0.005) and LC7-9 (r = 0.828, p<0.001). Secondly, 140 boys and 167 girls, aged 8-11 years were measured PA by LC method. WC and LC7-9 each were 13000-18000 counts and 16-32 minutes in week-day, and 8000-12500 counts and 8-18 minutes in week-end. PA analyzed by MANOVA were significantly higher in boys than in girls, and lower in week-end than in week-day, and decreased in proportion as grade. Present study suggests that LC method is a good measure of PA in free-living condition for elementary school students.