Data and code from: Locomotion control during curb descent: Bilateral ground reaction variables covary consistently during the double support phase regardless of future foot placement constraints

<p>During community ambulation, anticipatory adaptations in gait are key for navigating built, populated and natural environments. While stability or balance is critical while walking, some instability can assist in situations that demand maneuverability. Our goal was to identify whether healthy young individuals exhibit signs of such instability (or reduced stability) when they anticipate an upcoming maneuver. </p>

<p>Participants approached and stepped down from a curb, and in different experimental conditions, they were required to step onto visual targets on the floor for the step after stepping down from the curb. In some conditions, they expected the target to suddenly jump; this would require them to quickly adjust their gait to step onto the new target. </p>

<p>We used force plates to measure the ground reaction forces under both feet when the participant stepped down from the curb (with the two legs at different heights), and a motion capture system to measure the kinematics of the two legs. We analyzed the data associated with stepping down to identify anticipatory changes in stability to assist in the target stepping required for the subsequent step. </p>

<p>We computed stepping performance, and typical spatial-temporal gait variables (foot placements, step lengths and widths). We used the uncontrolled manifold analysis to determine whether the ground reaction forces under the two feet are coordinated to stabilize the motion of the body. Our main hypothesis was that the kinetic synergy indices, which quantify the stability, would be lower when the participants expect to change their movements to step on a target that might jump. </p>

<p>In contrast to our expectations, we observed that the kinetic synergy indices during curb descent were minimally influenced by expected foot targeting maneuvers for the subsequent step. Only the resultant moment in the frontal plane showed reduced stability when targeting was required, but the synergy index was still high, indicating that the resultant moment was stable. Furthermore, the synergy indices indicated that the main function of the ground reaction variables is to maintain stability of whole-body rotations during double support, and this prerogative was minimally influenced by the subsequent foot targeting tasks, likely because the cost of losing balance while descending a curb would be higher than the cost of mis-stepping on a visual target. Our work demonstrates the salience of stabilizing body rotations during curb negotiation and improves our understanding of locomotor control in challenging environments.</p>