Assessing the Validity of Attitude and Heading Reference Systems for Biomechanical Evaluation of Motions - A Methodological Proposal

Background: Attitude and Heading Reference Systems’ (AHRS) popularity in biomechanics has been growing rapidly over the past few years. However, the limits of operation and performances of such systems for motion capture are highly dependent upon their conditions of use and the environment they operate in. The objectives of this paper are to: (1) propose a methodology for the characterization of the criterion of validity of accuracy of AHRS in a human biomechanical context; and (2) suggest a set of outcome measures to assess the accuracy of AHRS. Methods: The criterion validity of accuracy is established using an optical motion tracking gold standard under standardized human motions. Results: Global assessment of accuracy is derived by comparing the orientation data provided by the AHRS to those given by the gold standard using a coefficient of multiple correlation. Peak values and RMS difference between both sets of orientation data are also analysed to complete the accuracy portrait. The methodology proposed herein is verified for the knee during regular walk. Conclusion: The proposed methodology and analyses take into consideration the complexities and processes required to assess the accuracy of AHRS in their context of use and provide a standardized approach to report.