Data from: Walking with wider steps changes foot placement control, increases kinematic variability and does not improve linear stability

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).