The purpose of this study was to assess daily physical activity and time spent on activities of various intensities, and to examine the relationship between daily physical activity and physical fitness in elementary school children. Subjects were 288 elementary school children (140 boys, 148 girls, 9.6±0.5 years). Daily physical activity was evaluated by accelerometers, worn around the waist for 10 days. Accelerometers calculated steps and vigorous intensity time (LC7-9: higher intensity than brisk walking). A physical fitness test (8 items) was applied to evaluate fitness in pupils. Total accelerometer steps (counts/day) were 18333±3869 for boys and 13957±2970 for girls on weekdays, and 11932±4827 for boys and 9767±4542 for girls on weekends, respectively. Time spent in LC7-9 (minutes/day) was 31±12 for boys and 20±7 for girls on weekdays. Positive associations were found between physical fitness and daily physical activities for many items. Above all, there was a relatively strong correlation between aerobic capacity and LC7-9 time. On the other hand, the correlations were low among girls. For fourth graders, in order to reach a B rank score in the physical fitness test, it was suggested that the total steps and LC7-9 time required at least 17000 steps, 30 minutes in boys, and 13000 steps, 20 minutes in girls, respectively.

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±1.0 years, 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.