Department of Cognitive Science, Rensselaer Polytechnic Institute, 110 8th Street, Troy, NY, 12180, USA.
Center for Perceptual Systems, University of Texas Austin, Austin, TX, USA.
Exp Brain Res. 2019 Jul;237(7):1673-1690. doi: 10.1007/s00221-019-05538-7. Epub 2019 Apr 12.
When walking over stable, complex terrain, visual information about an upcoming foothold is primarily utilized during the preceding step to organize a nearly ballistic forward movement of the body. However, it is often necessary to respond to changes in the position of an intended foothold that occur around step initiation. Although humans are capable of rapidly adjusting foot trajectory mid-swing in response to a perturbation of target position, such movements may disrupt the efficiency and stability of the gait cycle. In the present study, we consider whether walkers sometimes adopt alternative strategies for responding to perturbations that interfere less with ongoing forward locomotion. Subjects walked along a path of irregularly spaced stepping targets projected onto the ground, while their movements were recorded by a full-body motion-capture system. On a subset of trials, the location of one target was perturbed in either a medial-lateral or anterior-posterior direction. We found that subjects were best able to respond to perturbations that occurred during the latter half of the preceding step and that responses to perturbations that occurred during a step were less successful than previously reported in studies using a single-step paradigm. We also found that, when possible, subjects adjusted the ballistic movement of their center of mass in response to perturbations. We conclude that, during continuous walking, strategies for responding to perturbations that rely on reach-like movements of the foot may be less effective than previously assumed. For perturbations that are detected around step initiation, walkers prefer to adapt by tailoring the global, pendular mechanics of the body.
当在稳定、复杂的地形上行走时，视觉信息主要用于前一步，以组织身体近乎弹道式的向前运动。然而，通常需要对目标立足点位置的变化做出反应，这些变化发生在步幅开始之前。尽管人类能够在目标位置受到干扰时快速调整脚轨迹以响应摆动中的足部位置变化，但这些运动可能会破坏步态周期的效率和稳定性。在本研究中，我们考虑步行者是否有时会采用替代策略来响应干扰，这些策略对正在进行的向前运动干扰较小。实验中，被试者在地面上投影出的不规则间隔的踏足目标上行走，同时用全身运动捕捉系统记录他们的运动。在一部分试验中，一个目标的位置会在内外侧或前后方向上受到干扰。我们发现，被试者最能成功应对在前一步后半段发生的干扰，而在步幅中发生的干扰的反应不如以前使用单步范式的研究中报道的那样成功。我们还发现，当可能时，被试者会调整质心的弹道运动以响应干扰。我们得出的结论是，在连续行走中，依赖于足部类似伸手的运动来响应干扰的策略可能不如以前假设的那样有效。对于在步幅开始之前检测到的干扰，步行者更喜欢通过调整身体的整体摆动力学来适应。
