Initial Testing of a Novel Device Designed for Patients with Stroke – NU Virtual Ankle and Balance Trainer (NUVABAT)

Abstract

Motor control about the ankle and upright balance control are essential components of recovery following stroke.  We have developed a novel system (NUVABAT) to test and train these functions in standing or sitting. An instrumented footplate is interfaced with virtual reality (VR) software to enhance motor learning during task practice. In this study we describe initial testing of eight VR based games designed to assess/train standing balance and pre-gait activities using the system. Our purpose was to evaluate parameter settings and difficulty levels for these tasks with healthy subjects prior to testing patients with stroke.   The main input for the games was the center of pressure (COP) reading obtained from one leg while the subject stood on both legs during performance of the various tasks. We manipulated multiple parameter settings (e.g., target size, distance, sequence, and predictability; time on target; percent body weight on targeted leg) to devise 2 levels of difficulty for the tasks.   Two groups of subjects (10 younger, 10 older) were tested. Measures included: 1) Motor Performance (time to success (mean of 34 trials), # successes); 2) Perceived Difficultly (VAS rating, Modified Borg Scale); and 3) Usability Rating. Results indicate that our parameter set was sufficient to yield significant separation on motor performance measures (p<0.001) and ratings of perceived difficulty (p<0.001 to p<0.02) for easy vs. hard game levels that held across both younger and older subjects. Overall, system usability ratings were positive. Together, these results support proceeding to testing of the device on patients with stroke.