Parker H. Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA, USA; George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
South Atlanta High School, Atlanta, GA, USA.
J Biomech. 2022 Jan;130:110800. doi: 10.1016/j.jbiomech.2021.110800. Epub 2021 Oct 8.
Split-belt treadmills have become popular tools for investigating stability during walking by using belt accelerations to induce slip-like perturbations. While the onset timing of destabilizing perturbations is a critical determinant of an individual's stabilizing response, previous studies have predominantly delivered belt acceleration perturbations at heel strike or have not explicitly controlled onset as a percentage of the gait cycle. To address this gap, we 1) developed an algorithm to target transient increases in unilateral belt speed to begin at specific percentages of the walking gait cycle, 2) validated the algorithm's accuracy and precision, and 3) investigated the influence of different onset timings on spatial stability measures. We evaluated desired onset timings of 10, 15, 20, and 30% of the gait cycle during walking at 1.25 m/s and measured step lengths and widths, as well as anteroposterior and mediolateral margins of stability during the perturbed and four recovery steps in 10 able-bodied participants. From 800 perturbations, we found a mean (standard deviation) delay in onset timing of 5.2% (0.9%) of the gait cycle, or 56 (9) ms. We hypothesized later onset timings would elicit more stabilizing responses due to the less stable configuration of the body during late vs. early single stance. Our data generally supported this hypothesis - in comparison to earlier onset timings, later onset timings precipitated greater stabilizing responses, including larger step lengths, step widths, and anteroposterior/mediolateral margins of stability on the perturbed step, in addition to shorter step lengths and wider step widths on the first step post-perturbation.
分带跑步机已成为研究行走稳定性的流行工具，通过使用带加速度来诱导类似滑动的扰动。虽然失稳扰动的起始时间是个体稳定反应的关键决定因素，但以前的研究主要在脚跟触地时或没有明确将起始时间作为步态周期的百分比来控制。为了解决这一差距，我们 1）开发了一种算法，将单侧带速的瞬态增加目标设定为开始于特定的步行周期百分比，2）验证了算法的准确性和精度，以及 3）研究了不同起始时间对空间稳定性测量的影响。我们评估了在 1.25 m/s 的速度下行走时，步态周期的 10%、15%、20%和 30%的期望起始时间，并在 10 名健康参与者中测量了受扰和四个恢复步的步长和步宽，以及前后和左右稳定性边界。从 800 次扰动中，我们发现起始时间的平均（标准偏差）延迟为步态周期的 5.2%（0.9%），或 56（9）ms。我们假设较晚的起始时间会引发更多的稳定反应，因为在晚期单足支撑期间身体的稳定性较差。与较早的起始时间相比，我们的数据通常支持这一假设-较晚的起始时间引发了更大的稳定反应，包括受扰步的更大步长、步宽和前后/左右稳定性边界，以及受扰后第一步的更短步长和更宽步宽。
