978-1-5090-3053-8/17/$31.00 ©2017 IEEE Gaitzilla: Exploring the Effect of Embodying a Giant Monster on Lower Limb Kinematics and Time Perception Philippe Charbonneau, Mikael Dallaire-Côté, Sara Saint-Pierre Côté, David R. Labbe Laboratoire de recherche en imagerie et orthopedie (LIO) Centre de recherche du CHUM Ecole de technologie superieure Montreal, Canada david.labbe@etsmtl.ca Neila Mezghani LICEF Research Center Teluq University Montreal, Canada Sharif Shahnewaz, Imtiaz Arafat, Tanvir Irfan, Gayani Samaraweera, John Quarles Department of Computer Science University of Texas at San Antonio, USA Abstract—Previous research has shown that virtual embodiment can elicit behavioural change and increased motivation for exercise. However, there has been minimal research on how virtual embodiment can affect persons undergoing physical rehabilitation. We present a novel gait rehabilitation environment (Gaitzilla) in which the user embodies a gigantic Godzilla-like avatar while walking on a treadmill. He must step on tanks that are dispersed on the virtual street before him in order to survive. The required movements in the game are inspired by real gait training exercises that focus on foot placement and control. We present the result of a user study that explores the effect of embodying different avatars during these exercises on a lower limb movements and on user appreciation. The long-term objective of this research is to improve gait (i.e., walking patterns) rehabilitation through the use of 3D user interfaces and virtual embodiment. Keywords: Virtual embodiment, 3D User Interfaces, Gait rehabilitation, Serious games I. INTRODUCTION Gait rehabilitation is often a long term and repetitive process. From initial injury or onset of a disease, regaining significant mobility can take years [1]. During this period, patients are often required to perform many repetitive and/or painful exercises in order to regain their lost mobility. Many patients have motor control deficiencies of the lower limbs, which makes it difficult for them to place their foot on the ground where they intended to place it. Rehabilitation for such a problem requires repetitive practice of controlled foot placement, which can become boring for patients and therefore limit their motivation and perseverance in their rehabilitation program. To address this motivation issue, there have been many rehabilitation games that have been successful in helping to maintain motivation and make rehabilitation more entertaining [2]. Other games or virtual environments have been used to provide augmented biofeedback during rehabilitation. Providing augmented feedback is a common strategy to enhance motor learning by providing information about movement characteristics. Immersive virtual reality (VR), whereby a user is completely visually immersed in a virtual environment (VE), offers the added possibility of controlling a user’s visual self-representation in the VE. In other words, the user sees himself as an avatar rather than seeing his actual body. When visuomotor synchronicity is sufficiently high, this results in a subjective feeling of ownership of the avatar [1] (also called embodiment) where the user feels the avatar is his actual physical body. Recent studies in the field of psychology have shown that when embodying a virtual body, users modify their behavior to match that of their virtual body [2]. However, there has been minimal research on how virtual embodiment can affect persons undergoing physical rehabilitation. Embodiment could be useful in at least three regards in such a context. First, the characteristics of the embodied avatar (its nature and its physical proportions, for example) could lead to automatic changes in the user’s movement. This could be used to favour specific behaviours in a VE, such as movements of larger amplitude. Second, the embodiment of different avatars could further contribute to making the experience enjoyable, making rehabilitation seem less tedious and time consuming. Finally, avatar embodiment could be used to alter how a user visually perceives the movements he produces, in a kind of virtual mirror therapy [3], [4]. The current study is related to the two former. The objective of this study was to explore how embodying different virtual avatars in immersive VR impacts behaviour and motivation in rehabilitation exercises such as treadmill gait and foot placement tasks. We conducted an experiment where participants embodied a giant monster avatar and a similarly-scaled human avatar in an urban city virtual This research was supported by NSERC (Natural Sciences and Engineering Research Council of Canada and INTER (Interactive Technologies of Engineering in Rehabilitation) Research group of FRQNT.