Supplementary material from "Walking with wider steps changes foot placement control, increases kinematic variability and does not improve linear stability"

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).