Relationship Between the Walking Velocity Relative to the Slip Velocity and the Corrective Response

Purpose During walking, the slip velocity relative to the center of mass velocity can be one of the determinants of falls. We hypothesized that participants would select their strategy (classified by strategy type and measured by the distance of recovery landing or next forward stepping) according to both walking velocity and stance of legs. This study aimed to assess the relationship between the walking velocity relative to the slip velocity (maximum 1.6 m/s) and the corrective response and evaluated the element of the posture at the moment of slipping associated with the corrective response. Methods Ten healthy young adults showed leading leg perturbation in two isolated velocity conditions during over ground walking (slow: 0.9 m/s, fast: 1.6 m/s) using a built-in, double-belt treadmill. We defined the corrective response to perturbation as the change in the heel marker distance post-perturbation. We examined the postural parameters affecting the difference in corrective response. Results During fast walking, at a velocity near the maximum slip velocity, all participants overcame slipping and kept walking. During slow walking, at a velocity less than the maximum slip velocity, most of the participants took wide steps or stepped backwards and stopped walking. During slow walking, the step length (r = 0.84, p < 0.01) and the hip flexion angle (r = 0.78, p < 0.01) were strongly correlated with corrective response. Conclusion One of the targets of the therapeutic interventions may be expanding the hip’s range of motion to secure a stable base of support for elderly people with slow walking velocity.