Department of Athletic Performance, National Taiwan Normal University, Taipei, Taiwan.
Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, United States; San Francisco Giants Baseball Club, San Francisco, United States.
J Biomech. 2019 Aug 27;93:226-230. doi: 10.1016/j.jbiomech.2019.07.018. Epub 2019 Jul 25.
The present study quantified the effects of different shear cushion stiffness on the time to peak posterior shear force (TPPSF), peak posterior shear force (PPSF), average posterior loading rate (APLR), and maximum posterior loading rate (MPLR) at different locomotion speeds using a custom-made sliding platform, as well as to identify the optimal stiffness of shear cushion. Twelve male collegiate students (heel-strikers) performed walking at 1.5 m/s, jogging at 2.5 m/s, and running at 3.5 m/s. A custom-made sliding platform was used to provide the different shear cushion conditions. The shear cushion conditions were fixed (a fixed platform; control group), stiff (K = 2746 N/m), medium stiff (K = 2256 N/m), medium soft (K = 1667 N/m), and soft (K = 1079 N/m). The results showed that all cushion conditions produced sliding displacement and delayed the TPPSF during walking, jogging, and running compared with fixed condition. The APLR and MPLR were lowest under medium soft condition during walking, while the PPSF was similar between medium soft and soft conditions. For jogging and running, the PPSF as well as APLR and MPLR were the lowest under medium stiff condition except the maximum PLR was similar among stiff, medium stiff, and medium soft conditions during running. In conclusion, shear cushion produces appropriate sliding displacement and effectively delays the TPPSF to provide the musculoskeletal system additional time to absorb the impact and reduce loading. The present study demonstrates optimal stiffness of shear cushion at different traveling speeds and suggests that a shear cushion system can be applied in future designs of cushion structures.
本研究使用定制的滑动平台量化了不同剪切垫刚度对不同运动速度下峰值后向剪切力 (TPPSF)、峰值后向剪切力 (PPSF)、平均后向加载率 (APLR) 和最大后向加载率 (MPLR) 的影响，以及确定剪切垫的最佳刚度。12 名男性大学生（脚跟冲击者）以 1.5m/s 的速度行走、以 2.5m/s 的速度慢跑和以 3.5m/s 的速度跑步。使用定制的滑动平台提供不同的剪切垫条件。剪切垫条件为固定（固定平台；对照组）、硬（K=2746N/m）、中硬（K=2256N/m）、中软（K=1667N/m）和软（K=1079N/m）。结果表明，与固定条件相比，所有垫条件在行走、慢跑和跑步时都会产生滑动位移并延迟 TPPSF。在行走时，中软条件下的 APLR 和 MPLR 最低，而 PPSF 在中软和软条件下相似。对于慢跑和跑步，除了最大 PLR 在硬、中硬和中软条件之间相似外，中硬条件下的 PPSF 以及 APLR 和 MPLR 最低。总之，剪切垫产生适当的滑动位移，并有效地延迟 TPPSF，为肌肉骨骼系统提供额外的时间来吸收冲击并降低负荷。本研究展示了不同行进速度下剪切垫的最佳刚度，并表明剪切垫系统可应用于未来的缓冲结构设计。
