Reliability of a new diagnostic test for a functional balance measurement

The Virtual Balance Clinic is a system created to support the work of physiotherapists and physicians. It allows both, the diagnosis of a patient with impaired balance and the exercise performance control during personalized rehabilitation sessions. Rehabilitation relies on performing motor tasks hidden in games. The system includes two integrated devices, a posturographic platform and a 3D / 4D measurement system based on time-of-flight cameras (Kinect). Both devices are used to control and verify movement performance. Longitudinal data collection allows monitoring the progress of rehabilitation. In order to evaluate the effectiveness of rehabilitation, a special diagnostic module was created, which contains 3 tests assessing the balance. One of them is a functional balance test. It involves the rapid relocation of the COP (center of foot pressure) to areas indicated on the screen (Fig.1). During the test, two areas appear alternately. They have a specific width and distance between them. The displacement is done by leaning the body in a given direction and COP is drawn in real time on the screen of the monitor, that is placed in front of the patient. Since, the test was created for the purpose of the project realization, one need to establish its reliability and choose the best parameters for the width of the areas and the distance between them. Reliability is defined as information about the measurement error, which is about the stability of the results obtained by the subjects in repeated measurements (Bruton A. et. All 2000) Currently, one of the commonly used tests for measuring reliability is the calculation of intraclass correlation coefficients (ICC) (Shrout PE, Fleiss JL 1979, Koo TK, Mae YLi 2016).