Walking with wider steps
changes foot placement control, increases kinematic variability and does not improve linear stability
This webpage supports the following article about people walking with prescribed step widths
larger and smaller than the naturally preferred step widths.
If you need more information about
this article that is not available on this page, please
contact the corresponding author Manoj
Srinivasan.
Article
Title: Walking with higher prescribed step widths
decreases foot placement control gains with no change in linear stability
Journal citation: Royal Society Open Science. 4: 160627. 2017
Authors: Jennifer Perry and Manoj
Srinivasan
DOWNLOAD: Article PDF and Supplementary Information PDF and Data + Code.
Abstract: Walking humans respond to pulls or pushes on their upper body by changing where they place their foot on the next step. Usually, they place their foot further along the direction of the upper body perturbation. Here, we examine how this foot placement response is affected by the average step width during walking. We performed experiments with humans walking on a treadmill, both normally and at five different prescribed step widths. We prescribed step widths by requiring subjects to step on lines drawn on the treadmill belt. We inferred a linear model between the torso marker state at mid-stance and the next foot position. The coefficients in this linear model (which are analogous to feedback gains for foot placement) changed with increasing step width as follows. The sideways foot placement response to a given sideways torso deviation decreased. The fore–aft foot placement response to a given fore–aft torso deviation also decreased. Coupling between fore–aft foot placement and sideways torso deviations increased. These changes in foot placement feedback gains did not significantly affect walking stability as quantified by Floquet multipliers (which estimate how quickly the system corrects a small perturbation), despite increasing foot placement variance and upper body motion variance (kinematic variability).
Data
This zip file (270 MB). contains the raw motion capture data of all the walking trials and MATLAB code that computes the foot placement control gains, the foot placement variability, the torso state variability, the fraction of foot placement variability explained, and the Floquet multipliers. See readme.txt for more details.Funding
This work was supported in part by NSF CMMI grant 1254842.