Gait stability in virtual reality: effects of VR display modality in the presence of visual perturbations

Virtual reality (VR) has emerged as a pivotal tool for studying balance and postural control mechanisms, leveraging unpredictable visual disturbances that dynamically challenge visuomotor processing. However, the quantity and quality of information available in the visual field may differ between VR systems, potentially introducing conflict with the intended perturbation inputs. Consequently, the extent to which a VR system used in a visual perturbation paradigm influences its ability to elicit compensatory gait behaviors remains unclear. Here we investigate the impact of (1) VR display modality and (2) the direction of visual perturbations on spatiotemporal gait parameters and measures of stability in VR.

Participants were tasked with maintaining steady-state walking on a self-paced treadmill while viewing a VR scene presented in either a rear-projection curved screen immersive room (IR) or a head-mounted display (HMD). During trials with augmented visual perturbations, pseudorandom oscillations were combined with forward walking speed either in the anterior-posterior (AP), or medio-lateral (ML) direction. Linear mixed-effects models were used to analyze the impact of VR display type and visual perturbations on spatiotemporal gait parameters, stability measures, and joint kinematics.

For self-paced walking in matched VR optic flow, we found that the HMD increased the variability of several parameters related to walking speed control, but did not significantly impact any gait parameter average values. Superimposing visual perturbations along the ML axis increased gait variability and decreased walking stability in both VR systems, but the perturbations had stronger effects if presented in the HMD.

Together, these findings suggest that portable light-weight HMD systems can provide affordable, reliable tools for studying and training balance control and locomotion.