抄録
Shock attenuation property of sports surfaces is especially important not only for the athlete's performance but also for injury prevention. To evaluate the properties of the sports surfaces, some sports governing bodies often adopt friction tests and shock attenuation tests to determine the horizontal and vertical characteristics, respectively. Although the diagonal impacts are often observed in athletic sports, shock attenuation test only treats the vertical impact test. Therefore we developed a two-dimensional impact test device for examining the two-dimensional cushioning characteristics of sports surfaces in previous studies. To produce a simultaneous two-dimensional force against a test specimen, we incorporated a parallelogram linkage in the measuring system. The two-dimensional impact forces acquired from the sensor unit were compared with the data from the force plate for confirming the accuracy of the sensor unit with various initial angles and dropping heights and then the accuracy was ensured by the results. In this study, three different hardness of surfaces were examined for calculating the FR(Force Reduction) values not only the vertical component but also the horizontal component. As the results, both of vertical and horizontal impact forces which varied with initial impact angle and drop height were well represented by quadratic surface. By using these values, vertical and horizontal FR value of three kinds of surface were calculated from the experimental maximum force and estimated impact force with the same height and initial angle. Vertical FR values were increased with increasing the initial angle and dropping height in all surfaces. And the different patterns of horizontal FR values were observed in these surfaces.
