Dynamic balance in the frontal plane requires active control, which is accomplished largely through control of mediolateral foot placement. Individuals without mobility impairments have the ability to compensate for variability in foot-placement to maintain their balance; however, it is unknown how individuals respond to unexpected mediolateral perturbations to their foot placement that alter their balance control. The purpose of this study was to identify the biomechanical responses of individuals without mobility impairments to medial and lateral foot-placement perturbations during walking. Three-dimensional body segment kinematic and ground reaction force data were collected from 15 participants at 1.0 m/s and their self-selected speed on an instrumented treadmill. Dynamic balance was assessed by analyzing whole-body angular momentum in the frontal plane. We hypothesized that participants would respond to the perturbations with a combination of a lateral ankle strategy, hip adduction strategy and/or ankle push-off strategy to restore their balance. Overall, the medial perturbations adversely affected dynamic balance while lateral perturbations had little effect. Individuals responded to medial (lateral) perturbations with an increased (decreased) ankle inversion moment, which correlated to lateral (medial) shifts in their foot center of pressure. In addition, individuals responded to medial (lateral) perturbations with a decreased (slightly decreased) hip abduction moment. Contrary to our hypothesis, we did not observe an ankle push-off moment response but rather, a small response in the opposite direction. These results highlight the response of individuals without mobility impairments to unexpected foot-placement perturbations and provide a basis of comparison for those with impaired balance control.

额平面的动态平衡需要主动控制，这主要是通过控制脚内侧的位置来实现的。没有行动障碍的人有能力补偿足部位置的变化以保持平衡；然而，人们不知道个体如何对改变其平衡控制的足部位置意外的内侧扰动做出反应。本研究的目的是确定没有移动障碍的个体在行走过程中对内侧和外侧足部放置扰动的生物力学反应。从 15 名参与者以 1.0 m/s 的速度和他们在仪表化跑步机上自行选择的速度收集了三维体段运动学和地面反作用力数据。通过分析额平面中的全身角动量来评估动态平衡。我们假设参与者会通过侧踝策略、髋内收策略和/或踝关节推出策略的组合来响应扰动以恢复他们的平衡。总体而言，内侧扰动对动态平衡产生不利影响，而横向扰动几乎没有影响。个体对内侧（外侧）扰动的反应是增加（减少）脚踝内翻力矩，这与足部压力中心的外侧（内侧）转移相关。此外，个体对内侧（外侧）扰动的反应是髋关节外展力矩减少（略微减少）。与我们的假设相反，我们没有观察到脚踝推出力矩响应，而是相反方向的小响应。