Validity and reliability of an inertial measurement unit motion sensor as a tool for measuring cervical spine range of motion

OBJECTIVES: Accurate measurement of Cervical Range of Motion (CROM) is essential for quantifying motor deficits, designing interventions, and monitoring rehabilitation effectiveness. This study evaluated the validity and reliability of an Inertial Measurement Unit (IMU) (the Wiva Science) motion sensor, for assessing active CROM. METHODS: Sixty participants (22 male, 38 female) were enrolled for the validity study and fifty (32 male, 18 female) for the reliability study. Active CROM was measured at peak-range (participant's maximum comfortable active movement) and mid-range (participant-estimated halfway movement) positions using the IMU sensor and the Zebris motion capture system simultaneously. For reliability, a single examiner recorded three repetitions of each movement within a predetermined range. RESULTS: Concurrent validity was excellent, with Pearson's r ranged 0.902-0.996 (bias 0.08-3.67). The Intraclass Correlation Coefficient (ICC) for the IMU sensor ranged from 0.66-0.96, indicating moderate to excellent reliability. The Standard Error of Measurement was 0.26°-1.02°, and the Smallest Detectable Change ranged 1.93%-20.21%. CONCLUSION: The IMU motion sensor is cost-effective tool for CROM assessment, but its validity and reliability must be treated with caution. While clinically applicable, adequate trunk stabilization is essential for accuracy. To optimize results, device calibration is recommended prior to measuring each individual movement along its respective axis.