Overground walking while using a virtual reality head mounted display increases variability in trunk kinematics and reduces dynamic balance in young adults

Abstract

This study analyzed the effects of walking freely in virtual reality (VR) compared to walking in the real-world on dynamic balance and postural control. For this purpose, nine male and twelve female healthy participants underwent standard 3D gait analysis while walking randomly in a real laboratory and in a room-scale overground VR environment resembling the real laboratory. The VR was delivered to participants by a head-mounted-display which was operated wirelessly and calibrated to the real-world. Dynamic balance and postural control were assessed with (1) the margin of stability (MOS) in the anteroposterior (AP-MOS) and mediolateral (ML-MOS) directions at initial-contact, (2) the relationship between the mediolateral center of mass (COM) position and acceleration at mid-stance with subsequent step width, (3) and trunk kinematics during the entire gait cycle. We observed increased mediolateral (ML) trunk linear velocity variability, an increased coupling of the COM position and acceleration with subsequent step width, and a decrease in AP-MOS while walking in VR but no change in ML-MOS when walking in VR. Our findings suggest that walking in VR may result in a less reliable optical flow, indicated by increased mediolateral trunk kinematic variability, which seems to be compensated by the participants by slightly reweighing sensorimotor input and thereby consciously tightening the coupling between the COM and foot placement to avoid a loss of balance. Our results are particularly valuable for future developers who want to use VR to support gait analysis and rehabilitation.