The longitudinal and cross sectional study of junior high school and high school and college students about sprinting technic to improve sprinting velocity

本研究采用横断面研究和纵向研究相结合的方法，探讨技术因素（制动力和非支撑腿膝关节角度）与短跑速度的关系。我们在横断面研究中使用了12名男性运动员，在纵向研究中使用了8名不同表现水平的男性运动员。在纵向研究中，我们以2次/年的频率进行测量，总共4次。主要结果如下：无支撑腿C.G.的离心力约为300N，这是垂直力（约1500N）的1/5。这些结果表明，非支撑腿式重力加速度的离心力对地面反力有较大的影响。

The purpose of this study was investigate relationship between technical factor (braking force and knee joint angle of non-support leg) and sprinting velocity by cross sectional study and longitudinal study. We use 12thmale athletes in this cross sectional study and 8thmale athletes who difference performance level in this longitudinal study. And in longitudinal study we conducted measurements at frequency as two times / year and total four times.The main results were as follows. Centrifugal force of non-support leg C.G. is about 300N, this is 1/5 of vertical force (about 1500N). These results suggest that Centrifugal force of non-support leg C.G.is have a big influence on ground reaction force.