Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, the Netherlands.
Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, the Netherlands.
Gait Posture. 2021 Mar;85:110-116. doi: 10.1016/j.gaitpost.2021.01.004. Epub 2021 Jan 9.
When environmental conditions require accurate foot placement during walking (e.g., on a rough path), we typically walk slower to avoid tripping, slipping or stumbling. Likewise, hurrying too much is a common situational circumstance of walking-related falls. This suggests a tradeoff between walking speed and stepping accuracy in situations that demand precise foot placement.
How can this expected tradeoff between walking speed and stepping accuracy best be parameterized?
In Experiment 1, participants (n = 20) walked at five different speeds over an irregularly spaced sequence of projected stepping targets. Participants were instructed to place their feet accurately onto the targets, while following a constant-speed cue running alongside the walkway. Stepping accuracy was parameterized as overall (RMSE, root mean square error), variable (VE) and constant (CE) stepping errors, quantified over targets as well as per target. In Experiment 2, we determined preferred walking speed and stepping accuracy for regularly and irregularly spaced stepping targets.
Repeated-measures ANOVAs revealed that RMSE and VE grew linearly with increasing speeds, both over targets as well as per target. Per target CE varied in magnitude and sign with variations in inter-target spacing: for shorter inter-target spacing targets were overshot (CE > 0), while for longer inter-target spacing targets were undershot (CE < 0). This effect was stronger for faster speeds and for targets preceded by the shortest and longest inter-target spacing. Preferred walking speed and per-target VE did not differ between regularly and irregularly spaced targets.
Participants stepped less precisely when walking faster. The linear increase in VE with faster speeds was consistent with Schmidt's law regarding the speed-accuracy tradeoff. The systematic comparison of stepping errors over regularly and irregularly spaced stepping-target conditions further provided important clues on how to best parameterize stepping accuracy: per stepping target using VE (i.e., stepping inconsistency), complemented with CE (i.e., stepping bias) in case of irregular inter-target spacing.
当环境条件要求在行走时准确放置脚部（例如，在不平坦的路径上）时，我们通常会走得更慢以避免绊倒、滑倒或跌跤。同样，走得太快也是与行走相关的跌倒的常见情况。这表明在需要精确放置脚部的情况下，行走速度和步幅准确性之间存在权衡。
如何最好地参数化行走速度和步幅准确性之间的这种预期权衡？
在实验 1 中，参与者（n=20）以五种不同的速度在不规则间隔的投影步幅目标上行走。参与者被指示准确地将脚放在目标上，同时遵循沿着走道运行的恒定速度提示。步幅准确性被参数化为整体（均方根误差，RMSE）、变量（VE）和常数（CE）步幅误差，在目标上以及每个目标上进行量化。在实验 2 中，我们确定了规则和不规则间隔步幅目标的首选行走速度和步幅准确性。
重复测量方差分析显示，RMSE 和 VE 随着速度的增加呈线性增长，无论是在目标上还是在每个目标上。每个目标的 CE 随目标之间的间隔变化而变化：对于较短的目标之间的间隔，目标被过度射击（CE > 0），而对于较长的目标之间的间隔，目标被欠射击（CE < 0）。对于更快的速度和最短和最长目标之间的间隔，这种效果更强。首选行走速度和每个目标的 VE 在规则和不规则间隔目标之间没有差异。
参与者走得越快，步幅就越不准确。VE 随速度的线性增加与 Schmidt 定律关于速度-准确性权衡的观点一致。对规则和不规则间隔步幅目标条件下的步幅误差进行系统比较，进一步提供了有关如何最好地参数化步幅准确性的重要线索：对于每个步幅目标使用 VE（即步幅不一致性），在不规则目标间隔的情况下补充使用 CE（即步幅偏差）。
