A Novel Depth Image Analysis Method to Calculate the Anterior Reach of the Modified Star Excursion Balance Test

Abstract

In this paper, we present a novel method to measure the anterior (ANT) reach distance of the modified Star Excursion Balance Test (mSEBT). Using depth images obtained from the Microsoft KinectTM V2 sensor, we compared our results against a gold marker-based Vicon motion capture system. Seven healthy subjects participated in the study and were asked to perform five ANT reach trials of mSEBT bilaterally. Intra-class correlation coefficient (ICC), standard error of measurement (SEM), and smallest detectable distance (SDD) values were calculated. The Kinect demonstrated good reliability (0.7-0.9) against the Vicon in estimating absolute ANT reach and ANT reach normalized to leg length. The ICC (2,1) measurements were 0.75, 0.81 for absolute ANT reach distances and 0.81, 0.84 for normalized ANT reach measures, for the left and right foot, respectively. The SEM and SDD values of the Kinect were similar to previously reported normalized ANT reach manual measurements at 3.65, 10.11 for the left foot and 3.98, 11.04 for the right foot, respectively. For absolute ANT reach distances, the SEM and SDD values were 3.19cm, 8.85cm and 3.75cm, 10.41cm for the left and right foot, respectively. These results show potential capabilities of the depth image analysis method to provide reasonable accuracy in measuring ANT reach performance during the mSEBT.