Background

Previous work has linked the eccentricity of the net ground reaction force (GRF_net) to increased mediolateral instability during single-step voluntary and compensatory stepping responses. The present work sought to understand the extent to which such control mechanisms for mediolateral stability are present during gait.

Research question

How do gait velocity and step width constraints influence the kinetic control of mediolateral stability control among healthy participants?

Methods

25 participants performed three walking conditions – normal walking with self-selected speed and foot-placement, fast walking with self-selected foot-placement, and narrowbase walking – across a 10-meter walkway. Lateral instability was quantified by the mediolateral margin of stability (MoS_ML). The frontal-plane eccentricity of the GRF_net was calculated as the difference between GRF_net vector orientation and that of a line joining the coordinates of COP_net and COM. Two discrete time-points (P1 and P2) following foot-contact were examined, as they have been suggested to be indicative of proactive and reactive COM control, respectively. Task-related differences in the magnitude and timing of kinematic and kinetic outcome variables were analysed using one-way ANOVAs with repeated-measures.

Results

With constraints on step-width in narrow-base walking, participants exhibited reduced stability as evidenced by reduced MoS_ML, alongside reductions in the peak GRF_net eccentricity (θ_d) at P1. Participants exhibited no reduction in stability during fast walking, as revealed by the MoS_ML in part because of a similar onset of P1 within the gait cycle. P2 magnitude was larger in narrow-base walking relative to fast-walking, and occurred at an earlier point in the gait cycle.

Significance

Findings suggest proactive mechanisms (i.e. P1) may predominantly regulate mediolateral stability during walking. Reactive mechanisms (i.e. P2), however, may be capable of offsetting instability in situations where proactive mechanisms are insufficient.

中文翻译：

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地面净反力方向对行走过程中外侧稳定性的影响

背景

以前的工作已将净地面反作用力 (GRF _net )的偏心率与单步自愿和补偿性步进响应期间增加的内侧不稳定性联系起来。目前的工作试图了解在步态过程中这种中外侧稳定性控制机制的存在程度。

研究问题

步态速度和步宽约束如何影响健康参与者中间外侧稳定性控制的动力学控制？

方法

25 名参与者在 10 米长的人行道上进行了三种步行条件——自选速度和脚位的正常步行、自选脚位的快速步行和窄基步行。横向不稳定性通过稳定的内侧边缘 (MoS _ML )量化。GRF_网络的正面偏心率计算为 GRF_网络矢量方向与连接 COP_网络坐标的线的方向之间的差异和 COM。检查脚接触后的两个离散时间点（P1 和 P2），因为它们被建议分别表示主动和被动 COM 控制。使用具有重复测量的单向方差分析来分析运动学和动力学结果变量的大小和时间方面的任务相关差异。

结果

由于窄基步行中步宽的限制，参与者表现出稳定性降低，MoS _ML减少证明了这一点，同时在 P1 处峰值 GRF_净偏心率 (θ _d )减少。正如 MoS _ML所揭示的那样，参与者在快速步行期间没有表现出稳定性降低，部分原因是步态周期内 P1 的出现类似。相对于快速步行，窄基步行的 P2 幅度更大，并且发生在步态周期的较早点。

意义

研究结果表明，主动机制（即 P1）可能主要调节行走过程中的内侧稳定性。然而，在主动机制不足的情况下，反应机制（即 P2）可能能够抵消不稳定性。