Physio Avatar RM: Effects of Self-Avatar Integration With Foot-Elongated Avatar via Virtual Self-Touch on Human Gait

Virtual reality (VR) provides a controllable medium to couple perception and motor behavior in rehabilitation. This study investigated whether experiencing a foot-elongated avatar (FEA) via virtual self-touch (VST), which combines VR visual information and synchronized vibrotactile stimulation, is associated with body schema-related change and whether such change is reflected in motor behavior during obstacle crossing, indexed by maximum foot clearance (MFC). Twenty-two healthy young adults experienced two avatars in counterbalanced order: a life-size avatar (LA) and an FEA with a right-foot length that was 1.5 times that of the LA. The primary outcome measure was MFC while stepping over 10-cm and 30-cm virtual obstacles; the secondary outcome measures were perceptual drift in the perceived toe-tip position and questionnaire scores for the sense of ownership and sense of agency. The VST task produced significantly greater perceptual drift with the FEA than with the LA ( ${p} \lt 0.05$ , ${r} =0.813$ ). For the 30-cm obstacle, the MFC value was significantly greater with the FEA than with the LA ( ${p} \lt 0.05$ , ${r} =0.415$ ). In contrast, the questionnaire scores did not exhibit statistically significant group-level differences between the avatars. These findings suggest that body schema-related change after experiencing a FEA via VST was mainly limited to the perceptual aspect and was not clearly observed in the subjective aspect. Furthermore, the finding suggests that an aspect-specific body schema-related change may be associated with measurable gait adjustment during a more demanding obstacle-crossing task, although VST contribution cannot be isolated in the present design.