Hundza Sandra R, Gaur Amit, Brodie Ryan, Commandeur Drew, Klimstra Marc D
Motion and Mobility Rehabilitation Laboratory, University of Victoria , Victoria, British Columbia , Canada.
School of Exercise Science, Physical and Health Education, University of Victoria , Victoria, British Columbia , Canada.
J Neurophysiol. 2018 Apr 1;119(4):1528-1537. doi: 10.1152/jn.00979.2016. Epub 2017 Dec 20.
In young healthy adults, characteristic obstacle avoidance reflexes have been demonstrated in response to electrical stimulation of cutaneous afferents of the foot during walking. It is unknown whether there is an age-related erosion of this obstacle avoidance reflex evoked with stimulation to the tibial nerve innervating the sole of the foot. The purpose of this study was to identify age-dependent differences in obstacle avoidance reflexes evoked with electrical stimulation of the tibial nerve at the ankle during walking in healthy young and older (70 yr and older) adults with no history of falls. Toe clearance, ankle and knee joint displacement and angular velocity, and electromyograms (EMG) of the tibialis anterior, medial gastrocnemius, biceps femoris, and vastus lateralis were measured. A significant erosion of kinematic and EMG obstacle avoidance reflexes was seen in the older adults compared with the young. Specifically, during swing phase, there was reduced toe clearance, ankle dorsiflexion, and knee flexion angular displacement in older adults compared with the young as well as changes in muscle activation. These degraded reflexes were superimposed on altered kinematics seen during unperturbed walking in the older adults including reduced toe clearance and knee flexion and increased ankle dorsiflexion compared with the young. Notably, during mid-swing the toe clearance was reduced in the older adults compared with the young by 2 cm overall, resulting from a combination of 1-cm reduced reflex response in the older adults superimposed on 1-cm less toe clearance during unperturbed walking. Together, these age-related differences could represent the prodromal phase of fall risk. NEW & NOTEWORTHY This study demonstrated age-dependent erosion of obstacle avoidance reflexes evoked with electrical stimulation of the tibial nerve at the ankle during walking. There was significant reduction in toe clearance, ankle dorsiflexion, and knee flexion reflexes as well as changes in muscle activation during swing phase in older adults with no history of falls compared with the young. These degraded reflexes, superimposed on altered kinematics seen during unperturbed walking, likely represent the prodromal phase of fall risk.
在年轻健康的成年人中，已证实行走过程中对足部皮肤传入神经进行电刺激会引发典型的避障反射。目前尚不清楚，对支配足底的胫神经进行刺激所诱发的这种避障反射是否会随着年龄增长而衰退。本研究的目的是确定在无跌倒史的健康年轻和年长（70岁及以上）成年人行走过程中，对踝关节处的胫神经进行电刺激所诱发的避障反射是否存在年龄依赖性差异。测量了足趾离地间隙、踝关节和膝关节的位移及角速度，以及胫骨前肌、腓肠肌内侧头、股二头肌和股外侧肌的肌电图（EMG）。与年轻人相比，年长成年人的运动学和肌电图避障反射明显衰退。具体而言，在摆动期，与年轻人相比，年长成年人的足趾离地间隙、踝关节背屈和膝关节屈曲角位移减小，同时肌肉激活也发生了变化。这些退化的反射叠加在年长成年人自然行走时出现的运动学改变上，包括与年轻人相比，足趾离地间隙和膝关节屈曲减小，踝关节背屈增加。值得注意的是，在摆动中期，年长成年人与年轻人相比，足趾离地间隙总体减少了2厘米，这是由于年长成年人反射反应减少1厘米，叠加在自然行走时足趾离地间隙减少1厘米之上。总之，这些与年龄相关的差异可能代表了跌倒风险的前驱阶段。新发现与值得关注之处 本研究表明，在行走过程中对踝关节处的胫神经进行电刺激所诱发的避障反射存在年龄依赖性衰退。与无跌倒史的年轻人相比，无跌倒史的年长成年人在摆动期足趾离地间隙、踝关节背屈和膝关节屈曲反射明显减少，同时肌肉激活也发生了变化。这些退化的反射叠加在自然行走时出现的运动学改变上，可能代表了跌倒风险的前驱阶段。
