Background

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.

Research question

How can this expected tradeoff between walking speed and stepping accuracy best be parameterized?

Methods

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.

Results

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.

Significance

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.

中文翻译：

---

“浪费使浪费”：步行速度与目标步距精度之间的权衡

背景

当环境条件要求在步行过程中（例如，在崎path不平的道路上）准确放置脚部时，我们通常会走慢一些，以避免绊倒，滑倒或绊倒。同样，过于急促是与步行相关的跌倒的常见情况。这表明在需要精确放置脚的情况下，必须在步行速度和步速准确性之间进行权衡。

研究问题

如何在步行速度和踏步精度之间取得最佳平衡？

方法

在实验1中，参与者（n = 20）以五种不同的速度行走在不规则间隔的投影踩踏目标序列上。参与者被指示将脚准确地放在目标上，同时跟随人行道上的恒速提示。将步进精度参数化为总体（RMSE，均方根误差），变量（VE）和常数（CE）步进误差，对目标以及每个目标进行量化。在实验2中，我们确定了规则和不规则间距的踩踏目标的首选步行速度和踩踏精度。

结果

重复测量的方差分析显示，RMSE和VE随目标和每个目标的速度呈线性增长。每个目标CE的大小和符号随目标间间距的变化而变化：对于较短的目标间间距，目标被超调（CE> 0），而对于较长的目标间间距，目标被低于（CE <0）。对于较快的速度以及目标之间最短和最长的目标间距，此效果会更强。在规则和不规则间隔的目标之间，首选的步行速度和每个目标的VE并无差异。

意义

步行速度较快时，参与者的步距不太精确。VE随速度的增加呈线性增长，这与Schmidt关于速度精度折衷的定律是一致的。在有规律和不规则间隔的步进目标条件下进行的步进误差的系统比较进一步为如何最佳地设置步进精度提供了重要线索：每个步进目标使用VE（即步进不一致），并辅以CE（即步进偏差），以防万一不规则的目标间距。