Department of Kinesiology & Health Education, University of Texas, Austin, TX, USA.
Department of Engineering Science & Mechanics, Pennsylvania State University, University Park, PA, USA.
Gait Posture. 2021 Jan;83:88-95. doi: 10.1016/j.gaitpost.2020.09.031. Epub 2020 Oct 5.
Persons with lower limb amputation often experience decreased physical capacity, difficulty walking, and increased fall risk. To either prevent or recover from a loss of balance, one must effectively regulate their stepping movements. It is therefore critical to identify how well persons with amputation regulate stepping. Here, we used a multi-objective control framework based on Goal Equivalent Manifolds to identify how persons with transtibial amputation (TTA) regulate lateral stepping while walking without and with lateral perturbations.
When walking in destabilizing environments, do otherwise healthy persons with TTA exhibit greater difficulty regulating lateral stepping due to impaired control? Or do they instead continue to use similar strategies to regulate lateral stepping despite their amputation?
Eight persons with unilateral TTA and thirteen able-bodied (AB) controls walked in a virtual environment under three conditions: no perturbations, laterally oscillating visual field, and laterally oscillating treadmill platform. We analyzed step-to-step time series of step widths and absolute lateral body positions. We computed means, standard deviations and Detrended Fluctuation Analysis scaling exponents for each time series and computed how much participants directly corrected step width and position deviations at each step. We compared our results to computational predictions to identify the underlying causes of our experimental findings.
All participants exhibited significantly increased variability, decreased scaling exponents, and tighter direct control when perturbed. Simulations from our stepping regulation models revealed that people responded to the increased variability produced by the imposed perturbations by tightening their control of both step width and lateral position. Participants with TTA exhibited only a few minor differences from AB in lateral stepping regulation, even when subjected to substantially destabilizing lateral perturbations.
Since control of stepping is intrinsically multi-objective, developing effective interventions to reduce fall risk in persons with amputation will likely require strategies that adopt multi-objective approaches.
下肢截肢者通常会经历身体能力下降、行走困难和跌倒风险增加。为了防止或从平衡丧失中恢复，人们必须有效地调节他们的跨步动作。因此，确定截肢者如何调节跨步非常重要。在这里，我们使用了基于目标等效流形的多目标控制框架，以确定单侧小腿截肢（TTA）患者在无侧向干扰和有侧向干扰的情况下，如何调节侧向跨步行走。
在不稳定的环境中行走时，健康的单侧小腿截肢者是否会因控制受损而在调节侧向跨步时表现出更大的困难？或者他们是否仍然继续使用类似的策略来调节侧向跨步，尽管他们截肢了？
8 名单侧 TTA 患者和 13 名健康对照组（AB）在三种条件下在虚拟环境中行走：无干扰、侧向摆动视场和侧向摆动跑步机平台。我们分析了步宽和绝对侧向身体位置的逐步时间序列。我们计算了每个时间序列的平均值、标准差和去趋势波动分析标度指数，并计算了参与者在每一步直接纠正步宽和位置偏差的程度。我们将我们的结果与计算预测进行比较，以确定我们实验结果的潜在原因。
所有参与者在受到干扰时表现出明显增加的可变性、降低的标度指数和更紧密的直接控制。我们的步态调节模型的模拟表明，人们通过收紧对步宽和侧向位置的控制来应对施加的干扰产生的增加的可变性。TTA 参与者在侧向步态调节方面与 AB 参与者只有少数少数差异，即使他们受到了实质性的侧向干扰。
由于步态控制本质上是多目标的，因此开发有效的干预措施来降低截肢者的跌倒风险可能需要采用多目标方法的策略。
