Department of Mechanical and Aerospace Engineering, University of Central Florida, Orlando, Florida.
Disability, Aging, and Technology (DAT) Cluster, University of Central Florida, Orlando, Florida.
J Neurophysiol. 2022 Jan 1;127(1):38-55. doi: 10.1152/jn.00091.2021. Epub 2021 Dec 1.
Introducing unexpected perturbations to challenge gait stability is an effective approach to investigate balance control strategies. Little is known about the extent to which people can respond to small perturbations during walking. This study aimed to determine how subjects adapted gait stability to multidirectional perturbations with small magnitudes applied on a stride-by-stride basis. Ten healthy young subjects walked on a treadmill that either briefly decelerated belt speed ("stick"), accelerated belt speed ("slip"), or shifted the platform medial-laterally at right leg mid-stance. We quantified gait stability adaptation in both anterior-posterior and medial-lateral directions using margin of stability and its components, base of support, and extrapolated center of mass. Gait stability was disrupted upon initially experiencing the small perturbations as margin of stability decreased in the stick, slip, and medial shift perturbations and increased in the lateral shift perturbation. Gait stability metrics were generally disrupted more for perturbations in the coincident direction. Subjects employed both feedback and feedforward strategies in response to the small perturbations, but mostly used feedback strategies during adaptation. Subjects primarily used base of support (foot placement) control in the lateral shift perturbation and extrapolated center of mass control in the slip and medial shift perturbations. These findings provide new knowledge about the extent of gait stability adaptation to small magnitude perturbations applied on a stride-by-stride basis and reveal potential new approaches for balance training interventions to target foot placement and center of mass control. Little is known about if and how humans can adapt to small magnitude perturbations experienced on a stride-by-stride basis during walking. Here, we show that even small perturbations disrupted gait stability and that subjects could still adapt their reactive balance control. Depending on the perturbation direction, subjects might prefer adjusting their foot placement over their center of mass and vice versa. These findings could help potentially tune balance training to target specific aspects of balance.
引入意想不到的干扰来挑战步态稳定性是研究平衡控制策略的有效方法。人们对在行走过程中对小干扰的反应程度知之甚少。本研究旨在确定在小幅度多方向干扰下，个体如何逐步调整步态稳定性。10 名健康的年轻受试者在跑步机上行走，跑步机的速度会短暂减速（“stick”）、加速（“slip”）或在右腿支撑中期使平台横向移动。我们使用稳定裕度及其组成部分、支撑基础和外推质心来量化前后向和内外向的步态稳定性适应。在最初经历小干扰时，步态稳定性会受到干扰，稳定裕度在 stick、slip 和内侧偏移干扰中减小，在外侧偏移干扰中增大。对于同方向的干扰，步态稳定性指标通常受到更大的干扰。受试者在受到小干扰时既采用了反馈策略也采用了前馈策略，但在适应过程中主要采用了反馈策略。受试者在横向偏移干扰中主要使用支撑基础（脚部放置）控制，在 slip 和 medial shift 干扰中主要使用外推质心控制。这些发现提供了关于在逐步基础上应用小幅度干扰时步态稳定性适应程度的新知识，并揭示了针对脚部放置和质心控制的潜在新平衡训练干预方法。人们对在行走过程中逐步经历小幅度干扰时是否以及如何适应知之甚少。在这里，我们表明，即使是小的干扰也会破坏步态稳定性，而受试者仍然可以调整他们的反应性平衡控制。根据干扰的方向，受试者可能更喜欢调整他们的脚部位置而不是质心，反之亦然。这些发现可能有助于有针对性地调整平衡训练，以针对平衡的特定方面。
