Validity, reliability, and user perspectives of the newly developed joint angle measurement system with inertial measurement unit sensors

PurposeWe aimed to evaluate the applicability of the newly developed joint angle measurement system consisting of six-axis inertial measurement unit sensors and tablet-based application that measure and store angular velocity and acceleration data for estimating joint angles. Materials and MethodsThe tablet-based application was used to calculate the orientation angles from angular velocity and acceleration data measured using a single sensor. The relative angles were calculated using the data from multiple sensors. In experiment 1, the validity and reliability of calculated angles was examined using a test device. In experiment 2, the angles of five joints were calculated in four healthy participants using attached inertial measurement unit sensors; the angles were compared with universal goniometer-measured values. In experiment 3, usability and satisfaction were evaluated with the System Usability Scale (SUS) and a Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST)-like scale. ResultsIn experiment 1, the mean difference of the time-series data between those obtained by the developed system and test device was 0.2{degrees} for all axes. In experiment 2, the mean difference of the integrated data was 0.2{degrees}. The mean difference for all joints was 5{degrees}, indicating that the measurement system is comparable to the universal goniometer. In experiment 3, the median SUS and QUEST-like scale scores were 81 and 4.0, respectively, indicating high usability and satisfaction. ConclusionThe newly developed joint angle measurement system has high accuracy in measuring angles and sufficient validity in application to human joint angles, with high usability and user satisfaction.