CAUSAL RELATIONSHIPS OF DAILY PHYSICAL ACTIVITY TO PHYSICAL FITNESS AND MOTOR ABILITY IN JAPANESE YOUTH

Abstract

The levels of physical fitness and motor ability in Japanese youth have been lowering during the last two decades when referenced to the national statistics on physical fitness and motor ability. PURPOSE To examine causal relationship of the level of daily physical activity to physical and motor ability in Japanese youth. METHODS The national survey on health promoting lifestyle and physical fitness measurement using Japan Fitness Test was carried out in 2001 with 10.517 samples, boys and girls in elementary and secondary schools, aged 6 to 17. The questionnaire items on daily physical activity, meals and sleep were investigated. The eight physical fitness test items were grip strength for muscle strength, sit-ups for muscle power and endurance, sit and reach for flexibility, standing long jump for muscle power, side stepping for agility, 20-m shuttle run for aerobic endurance, 50 m dash for sprinting ability, handball throw for ball throwing ability, and total physical fitness score. Energy expenditure during daily physical activity was measured using pocket type accelerometers. Structural equation modeling (SEM) and applied tree-based method by CART of data mining technique were utilized to confirm causal relationship of the level of physical activity to physical fitness and motor ability. RESULTS The goodness-of-fit indices of serial causal effect models among participation in sports clubs, weekly exercise and sports participation, daily physical activity and physical fitness were sufficient in both boys and girls. All beta coefficients of standardized solution on the serial models were significant (P < .05) in both boys and girls. The split variables on the CART models were weekly exercise and sports participation, participation time of exercise and sports, and a well balanced meal in both boys and girls. CONCLUSION A significant causal relationship of weekly sports participation to physical fitness and motor ability was statistically confirmed.