Recent advancements in virtual reality (VR) have opened up new areas of study. For instance, little is known to what extent humans can modify their walking pattern over time to accommodate a Virtual Environment (VE) while they experience visual perturbations. Sensory discordances in the form of oscillations of the visual field are of interest to clinicians who study how the reliance on visual feedback and the propensity for visuomotor adaptations challenge the ability to maintain balance during walking. Virtual Reality technology provides a safe environment for analyzing how humans react and adapt to various types of discordant sensorimotor stimulations.
The pilot study, Gait adaptations during overground walking and multidirectional oscillations of the visual field in a virtual reality headset, published in Gait & Posture, investigated the propensity for visuomotor adaptations of spatio-temporal gait parameters when walking in a Virtual Environment and experiencing continuous antero-posterior (AP) and medio-lateral (ML) oscillations of the visual field. Protokinetics’ Zeno Walkway and PKMAS were used to collect data for the study.
Twelve healthy young adults were recruited for the experiment. Participants walked for 6 min on the Zeno Walkway at a comfortable speed in 4 different conditions:
- Walking in the Real Environment (RE).
- Walking in the virtual environment (VE) while wearing a VR headset (HTC VIVE) calibrated so that the virtual walkway was aligned and mapped one-to-one with respect to the physical walkway.
- Experiencing a first-person view of themselves walking in the virtual walkway without corresponding movements of their self-representation (i.e., their body was not rendered in the VE).
- Walking in the VE while experiencing medio-lateral (ML) or antero-posterior (AP) visual perturbations.
Each condition with the headset was followed by a 3-minute Real Environment (RE) walking condition to washout possible aftereffects of VR. Participants were aware that they might be perturbed in the AP or ML conditions but were unaware of the magnitude, the direction, or the timing of the perturbations. Before the intervention started, they were instructed to maintain balance and keep walking.
Spatiotemporal gait parameters were measured using the PKMAS gait recording and analysis software of the Zeno walkway. Stride length (SL), stride width (SW), and stride time (ST) were calculated at both left and right heel strikes. SL was defined as the distance between the corresponding successive heel points of the same foot, measured parallel to the direction of progression. SW was calculated as the perpendicular distance between the line connecting the two ipsilateral foot heel points and the contralateral heel point. ST was estimated as the time period between the first consecutive contact of the same foot.
Previous experiments showed that visual perturbations affect gait in older adults more than healthy young subjects, increasing their reliance on visual feedback to maintain balance. Additionally, aftereffects in the real environment are correlated with the rate of adaptation during the periods of sensorimotor discordance.
The pilot study may have positive implications for early detection and remediation of gait disorders, as sensory acuity often deteriorates with aging. Similar to what was already done for improving the reaction to slipping perturbations with treadmill visual-perturbation training, an over-ground training paradigm with continuous visual perturbations could be developed to train subjects to refine the relative weighting of different sensory feedbacks, through the exposure to visual perturbation in a more ecological condition.