Benefits of functional calibration for estimating elbow joint angles using magneto-inertial sensors: preliminary results

Magneto-Inertial Measurement Unit (M-IMU) sensors are more and more used in motion analysis as they allow for “Out-of-the lab” measurements. This technology requires a calibration process to transform sensor movement data in anatomical information such as joint angles. Although the literature proposes several ways of calibration, it is not straightforward for the researcher to know the pros and cons of each method. This work proposes to study different ways of generating segment axes using M-IMUs, joint by joint. These segment axes are not enforced to be orthonormal (as it is generally done in the literature) and are built using either static postures or functional movements. This abstract presents preliminary results for the elbow joint angles. Four M-IMU-based methods using different calibrations are compared to the gold-standard method, during elbow maximal flexion-extensions (FE). Results show the M-IMU method that uses the functional calibration for generating the elbow FE axis calculates less motion in the two unexpected elbow degrees of freedom (abduction-adduction and pronation-supination), than the other methods. This preliminary study highlights the benefits of functional calibration associated to M-IMU technology for limiting cross-talk effect. Further results using data from several volunteers are needed to confirm these conclusions. The use of functional calibration dedicated to the wrist and shoulder joints represent other ways of investigation.