不同着地方式跑步的神经肌肉调谐规律——基于地面反作用力的时频分析

The neuromuscular tuning law under different foot strike landing of running——A time frequency analysis of ground reaction force

采用连续小波变换分析跑步支撑相地面反作用力的时频分布特点,结合下肢刚度和下肢肌肉激活水平,探讨不同着地方式跑步时着地缓冲的神经肌肉调谐。分别采集前足(FFS)、全足(MFS)和后足(RFS)3种着地方式跑步时地面反作用力和下肢肌肉表面肌电信号。结果显示,FFS支撑相的最大小波功率和小波功率总和明显高于MFS和RFS(P<0.05)。支撑相前20%阶段,FFS表现出明显较小的最大伪频率(PFmax),且PFmax出现时间也明显较晚。此外,MFS的下肢刚度明显较高(P<0.05),FFS的下肢肌肉激活水平均较高。研究表明,跑者通过改变着地方式可调整着地时的冲击频率,与MFS和RFS相比FFS的冲击频率和下肢刚度均较小,不利于下肢弹性能的储存和利用,加上较高的下肢肌肉激活水平,易引起机体疲劳。

A continuous wavelet transform analysis was used for characterizing and manipulating the ground reaction whose statistics vary in time during the running stance phases and to investigate the neuromuscular tuning law by considering the lower limb stiffness and the activation degree of lower extremity muscles.17 healthy males ran at forefoot(FFS),mid-foot(MFS)and rearfoot strikes using natural stride speed,and ground reaction forces and lower extremity muscle surface EMG were assessed during stance.The results showed that the maximum signal power(Pmax)and the sum of signal power are significantly higher in the stance of FFS than in MFS and RFS(P<0.05).In the early 20%of stance,the FFS exhibited a significantly less maximum pseudo-frequency(PFmax),and the PFmax also appeared significantly later.In addition,MFS exhibited significantly stiffer lower limb stiffness(P<0.05),while FFS had higher levels of lower extremity muscle activation in both.In conclusion,it is possible for runners to adjust the impact frequency by changing footstrike landing,FFS has a lower impact frequency and lower limb stiffness compared with MFS and RFS,which is not conducive to storage and utilization of lower limb elastic energy,and the higher level of lower extremity muscle activation easily led to fatigue.