Immediate responses and adaptations to mediolateral optic flow perturbations are speed-dependent and larger at slower gait speeds, with walking at slow speeds inducing greater immediate responses in mediolateral gait parameters compared to walking at faster speeds.
Key Findings
Results
Slow walking speed induced greater immediate responses in mediolateral gait parameters compared to faster speeds upon exposure to mediolateral optic flow perturbation.
Twenty-one healthy young adults (23.43 ± 4.19 years) participated in the study.
Trials were conducted at three speeds: 0.6, 1.2, and 1.8 m/s on an instrumented treadmill.
Mediolateral margin of stability (MoS) also showed a significant speed-dependent immediate response (p < 0.001).
The perturbation protocol consisted of a 3-min baseline, 8-min mediolateral optic flow perturbation, and 3-min post-perturbation phase.
Results
Adaptations during prolonged perturbation exposure were larger at faster versus slower speeds for gait parameters in the direction of movement.
Step length (SL) showed a significant speed-by-phase interaction during the perturbation phase (p = 0.007).
The adaptations from early to late perturbation were larger at faster speeds compared to slower speeds for SL.
This contrasts with the pattern seen for mediolateral parameters, which showed larger immediate responses at slower speeds.
The perturbation phase lasted 8 minutes, allowing comparison of early versus late perturbation responses.
Methods
Three separate repeated-measures ANOVAs were used to compare gait parameters across perturbation phases and speeds.
The three ANOVAs compared: baseline vs. early perturbation, early vs. late perturbation, and baseline vs. post-perturbation.
Ground reaction forces and 3D motion data were collected to calculate mediolateral MoS, mean step length, step width, and their variabilities.
A Speed by Phase design was employed for each ANOVA.
All 21 participants completed trials at all three gait speeds (0.6, 1.2, and 1.8 m/s).
Discussion
The responses to prolonged optic flow perturbation were interpreted as step-to-step adaptations that are speed-dependent.
Adaptations across the perturbation phase differed depending on gait speed.
The authors suggest these step-to-step adaptations may inform future interventions and studies on gait speed selection.
Post-perturbation responses (baseline vs. post-perturbation comparison) were also examined as part of the three-phase analysis.
The overall pattern indicated that the direction of speed-dependency differed between mediolateral parameters and anterior-posterior (step length) parameters.
Methods
Optic flow perturbation was delivered in the mediolateral direction during treadmill walking across a range of speeds.
The study used an instrumented treadmill combined with a mediolateral optic flow perturbation paradigm.
Three walking speeds (0.6, 1.2, and 1.8 m/s) were tested to represent slow, preferred, and fast walking.
The perturbation phase lasted 8 minutes, preceded by a 3-minute baseline and followed by a 3-minute post-perturbation phase.
Outcome measures included mediolateral margin of stability (MoS), step length, step width, and variability of each parameter.
Wu C, Buurke T, den Otter R, Lamoth C, Veldman M. (2026). The effects of gait speed on the responses to immediate and prolonged exposure to mediolateral optic flow perturbation in healthy young adults.. Human movement science. https://doi.org/10.1016/j.humov.2026.103467