Effect of unilaterally manipulating the step length of an embodied avatar on gait symmetry in healthy adults.

In virtual reality, mapping one's body movements to an avatar creates a sense of embodiment, where the avatar is perceived as part of one's own body. Previous studies have indicated that introducing a spatial offset between the avatar's movements and the user's real movements can lead to users unconsciously adjusting their movements to align with the avatar. However, while the effects of such spatial distortion have been studied in the movement of the upper body, little is known about its influence on gait. This study aimed to assess whether altering the step length of an embodied avatar induces a more asymmetrical walking pattern. Thirty healthy participants underwent a treadmill walking experiment while wearing a head-mounted display that displayed an embodied avatar mirroring their movements from a first-person perspective. An algorithm was developed to dynamically increase one of the avatar's step lengths in real-time, introducing gait asymmetry. The effect of step length manipulation on gait asymmetry was assessed under two conditions, where the avatar's step length was gradually increased unilaterally for either the dominant or non-dominant leg. Results indicated that participants did not significantly adjust their gait symmetry to match the avatar's increased step length, whether it was applied to the dominant or non-dominant leg. These findings suggest that healthy participants may be more resistant to visual feedback-induced changes provided by an embodied avatar, in contrast to the adjustments observed in upper-body movements. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1007/s10055-026-01406-2.