Comparing a friction-based uni-directional treadmill and a slip-style omni-directional treadmill on first-time HMD-VR user task performance, cybersickness, postural sway, posture angle, ease of use, enjoyment, and effort

Abstract

Treadmills allow users to translate their real world walking into movement in virtual worlds. Conventional treadmills used for fitness can be repurposed for users to move around in virtual reality, but permit walking in only one direction (uni-directional). Treadmills that allow walking in any direction (omni-directional) are available, in which users walk-in-place and their feet slip on a low-friction surface. Given that users can experience cybersickness and postural instability in virtual reality, this study explored user performance and side effects of using two different walking platforms: a conventional uni-directional treadmill and a slip-style omni-directional treadmill (Virtuix OMNI).All participants (n = 46) played a game in which they collected items distributed around a virtual world. Participants moved around the virtual world by walking on the conventional uni-directional treadmill (for 10 minutes) and on the omni-directional treadmill (for 10 minutes), whilst in HMD-VR, with a 5-minute break between platforms. Measurements of cybersickness, task achievement, distance covered, posture, postural sway and user experience (ease, enjoyment, and effort) were collected.Participants experienced significantly higher total cybersickness after walking on the slip-style omni-directional treadmill compared to after walking on the uni-directional treadmill (p=.003), and significantly higher Nausea and Oculomotor cybersickness after walking on the slip-style omni-directional treadmill compared to after walking on the uni-directional treadmill (p<.001 and p=.005 respectively). Participants had lowest postural sway after using the uni-directional treadmill compared to after using the omni-directional treadmill (p=.052). Participants completed significantly more of the task (p<.001) and walked further (p<.001) on the uni-directional treadmill compared to the omni-directional treadmill, and their posture angle (back tilt angle) was significantly more forward on the omni-directional treadmill compared to the uni-directional treadmill (p<.001). Significant differences were found with participants reporting walking on the omni-directional treadmill to be more difficult (p<.001), require more effort (p<.001) and be less enjoyable (p=.005), and changing direction to require more effort (p=.010), than compared to the uni-directional treadmill.This study recommends that alternatives to slip-style locomotion treadmills be developed due the non-natural walking action required to use slip-style platforms and the consequent negative psychophysiological impacts of their use with HMD-VR.