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.