Reliability and validity of estimated angles information assessed using inertial measurement unit-based motion sensors.

This article focuses on evaluating the reliability and validity of angle measurements obtained from inertial measurement unit (IMU)-based sensors compared to a three-dimensional (3D) motion analyzer in controlled rotational motion. Using direct current (DC) motors to generate uniform circular motion at various speeds, the study found that the IMU-based sensor demonstrated high absolute reliability and validity, with measurement errors ranging from 0.2° to 3.9° and intraclass correlation coefficients (ICC) above 0.9 when compared to Euler angles from the 3D motion analyzer. Although relative reliability measured by ICC (1,1) was low, time-series waveform agreement was consistently high (cross-correlation function >0.9), indicating strong consistency in angle tracking across trials. The findings suggest that IMU-based sensors can provide accurate angle information suitable for rehabilitation settings, particularly for movements within the tested velocity range, while noting limitations in assessing multi-axis rotations and very high-speed motions.