CHARACTERIZATION AND VALIDATION OF VIRTUAL REALITY WALKING SIMULATOR

Abstract

Purpose/Hypothesis: Virtual Reality (VR) has been proposed as a strategy for rehabilitation. To measure the potential of new VR devices they need to be characterized and compared to their real world counterparts. The primary purpose of this study was to characterize and validate the gait of individuals who walked on a VR walking simulator (WS) by comparing it to the kinematics and velocity of overground walking. The secondary purpose was to determine if the presence of the virtual environment (VE) modified walking characteristics. We hypothesized that walking velocity would be greater overground and slowest without the VE. Number of Subjects: Ten healthy subjects (2 male and 8 female) ages 24–53 without musculoskeletal injuries or neuromuscular pathology participated. Materials/Methods: Gait step length and velocity were collected (three trials) as participants walked at their self selected speed on a Gait Rite mat. Participants wore a harness and refective markers on the foot, ankle, knee, hip and trunk. They stood on the WS with each foot secured on a robotic platform, a harness attached to an unweighing frame, facing a screen. Unweighed 40% of their body weight they practiced walking on the WS (2–8 min.) until achieving the criterion gait pattern. Data were collected for four street crossing trials, walk without VE (2), walk with VE (2). An auditory tone or the VE green light prompted participants to begin walking. Kinematics were acquired using a 6 camera Peak system at 60 Hz. Joint angles were calculated for push of and initial contact by averaging the peak angle of three steps. Velocity data were averaged from the x-translation plots of the ffth metatarsal. Joint excursions from push of to initial contact-loading response were compared to normative data. Differences between overgound walking velocity and step length relative to the mobility simulator with and without the VE were assessed using a repeated measures ANOVA (alpha level= .05). Results: Walking velocity and step length were significantly greater for overground walking (1.5 m/sec; .79 m) compared with the mobility simulator with (.22 m/sec; .17 m) and without (.21 m/s; .18 m) the VE. The average joint excursions on the mobility simulator for push of to initial contact-loading response were 34 (knee) and 18 (ankle) degrees; compared to a range from push of to initial contact-loading response of 22–40 (knee) and 10–20 (ankle) degrees in normal gait. Conclusions: Walking in the VE resulted in pronounced decreases in temporal distance measures of gait however joint excursions were comparable to normal gait. There were no differences in gait velocity, step length or joint excursions when walking on the mobility simulator with and without the VE. The mechanics of the robot limit step length however, changing street crossing time in the VE may increase walking velocity. Clinical Relevance: Selected aspects of gait were preserved in the WS while others were not. Transfer of training from the walking simulator to real world walking still needs to be determined.