Upper limb kinematics and inertial sensors: which calibration for the best accuracy?

Introduction: Magneto-Inertial Measurement Unit sensors (MIMU) are increasingly used in motion analysis as they allow for ambulatory measurements. One of the research points that deserve more investigation for MIMU-based upper limb kinematics is the inter-calibration comparison. The present study compares three different classes of calibration in terms of accuracy for the generation of wrist, elbow and shoulder (humero-thoracic) joint angles, during maximal amplitude movements.
Methods: Ten subjects, equipped with four MIMU on their right upper limb, repeated five times an experiment composed of a calibration session followed of seven maximal test movements. An optoelectronic system was used as the reference system of measurement for the kinematics (REF).
Results: For all flexion/extension angles, the accuracy of the three MIMU calibrations was very good and equivalent (0.85CMCip0.99). Lower accuracy and disparities among calibrations could be observed for specific angles, without any constant predominance of a particular calibration.
Conclusion: This study highlights that the three classes of calibration provide good level of accuracy considering CMCip, without any significant difference between them. For a complete evaluation of MIMU-based upper limb kinematics, reproducibility and interpretation of joint angle should also be considered key criteria.