Can Treadmill Walking Replicate Natural Walking? Optimizing Speed, Platform Tilt, and Training Duration on a Cyberith Virtualizer Elite 2

Locomotion is central to human navigation and spatial learning, with natural walking offering the most effective movement in immersive virtual environments (IVEs) due to its rich proprioceptive and vestibular feedback. However, space constraints often limit natural walking in IVEs, prompting the use of omnidirectional treadmills. The Cyberith Virtualizer Elite 2 enables users to walk in place by sliding their feet on a low-friction, tiltable platform while secured in a harness. It allows control over both tilt angle and walking speed, offering researchers flexibility in adjusting sensorimotor cues. In this study, we examined how tilt angle, speed, and training duration affect distance perception and cybersickness. In Experiment 1, we tested three tilt angles (0°, ~8.5°, ~17°) and three speeds (0.8×, 1.0×, 1.2× treadmill speed) during blind walking. A slower speed (0.8×) aligned best with natural walking and minimized cybersickness; users preferred the ~8.5° tilt. Additional analysis identified ~0.7× speed with ~8.5° tilt as preferred. In Experiment 2, we varied training durations (3, 6, or 9 minutes) and found that, with the preferred setup, treadmill distance judgments were comparable to natural walking. At least 6 minutes of training was sufficient for adaptation. These findings offer practical guidance for configuring treadmill locomotion in virtual reality research.