Taiki Yoshida

Abstract We aimed to evaluate the applicability of a newly developed joint angle measurement system comprising six-axis inertial measurement unit sensors and tablet-based application for estimating joint angles from angular velocity and acceleration data. The application calculated orientation angles from single sensor data, with relative angles calculated using multiple sensors. In experiment 1, validity and reliability were examined using a test device. In experiment 2, static angles of five joints were calculated in four healthy participants using attached sensors and compared with universal goniometer values. In experiment 3, usability and satisfaction were evaluated using the System Usability Scale (SUS) and Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST)-like scale. In experiment 1, mean difference and root mean squared error (RMSE) between the developed system and test device were < 0.2° and < 1.0°, respectively, across all axes. In experiment 2, when data from all joints were pooled, mean difference and RMSE were 0.2° and 3.8°, respectively. Mean difference and RMSE across each joint were < 5°, indicating the system is comparable to universal goniometer. In experiment 3, median SUS and QUEST-like scores were 73.8 and 4.0, respectively, indicating good usability and satisfaction. The developed system has high accuracy and sufficient validity for human joint angles, with good usability and satisfaction.

Purpose: We 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 Methods: The 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. Results: In experiment 1, the mean difference of the time-series data between those obtained by the developed system and test device was <0.2 degree for all axes. In experiment 2, the mean difference of the integrated data was 0.2 degree. The mean difference for all joints was <5 degree, 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. Conclusion: The 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.