WITHIN-SUBJECT REPEATABILITY AND BETWEEN-SUBJECT VARIABILITY IN POSTURE DURING CALIBRATION OF AN INERTIAL MEASUREMENT UNIT SYSTEM

Inertial measurement units (IMUs) are a valuable tool for field based sports research, but within- and between-subject comparisons may be affected by variation in the 0° position established by a standing calibration position. This study assessed within-subject repeatability and between-subject variability in IMU sensor orientations during calibration. Calibration posture was reliable within-subjects given standardised instructions (typical error \u3c 1.9°). Sensor angles relative to a global vertical axis had large between-subject ranges for upper spine (21–35°), lower spine (1–23°) and pelvis (11–35°), while lower limb segment angles had much lower variability (0-6°). Thus, a standing calibration posture is repeatable within participants given suitable instructions, however variability in standing posture may need to be accounted for before making between-subject comparisons, particularly with regard to spine and pelvis segments