Abstract
The present study was conducted to clarify causal structures among sprint performance indices and body movements during sprinting in elementary school boys. Three hundred and eighty three boys in the 1st to 6th grades performed a 50-m sprint, and the step length index, the step rate index (in which effects of differences in body height were eliminated) and body movements at ground contact were measured at the 35-m point from the sprint start. Path analysis was applied to the measured parameters at each stage for low (1st and 2nd), middle (3rd and 4th) and upper (5th and 6th) grades. From the results, the following trends were suggested: 1) There appeared to be a causal structure among indices of sprint performance and body movements. 2) For boys in all grades, the knee flexion and forward inclination of the thigh in the recovery leg were important for increasing the step length index, whereas backward inclination of the thigh in the recovery leg and forward inclination of the lower thigh in the support leg were important for increasing the step rate index. 3) For boys in the lower grade, forward inclination of the body had a greater positive effect on the height of the step length index than in other grades. 4) In the middle grade, knee flexion of the recovery leg had a greater positive effect on the height of the step length index than in other grades. 5) In the upper grade, forward swing of the thigh in the recovery leg had a greater positive effect on the height of the step rate index, although inclination of the lower thigh in the support leg was higher than in other grades.
