Multibody kinematic optimisation vs body fat: A performance analysis

We have analysed the performance of mulitbody kinematic optimisation methods in reducing soft tissue artefacts for subject data of varying body fat percentages. Multibody kinematic optimisation methods are a critical aspect of movement analysis using musculoskeletal modelling software. By minimising soft tissue artefacts, they help in achieving higher fidelity joint kinematics and dynamics analyses. Prior studies have not examined the performance of multibody kinematic optimisation on subjects of varying body fat percentages. Herein, we: 1) have analysed the efficacy of three different multibody kinematic optimisation methods on varying body fat percentages, 2) implemented a novel weighting scheme to reduce error irrespective of body fat percentages. Residual error using gait data of 50 participants of varying body fat percentages was calculated through inverse kinematic analysis using OpenSim(c) musculoskeletal modelling software. The analysis was repeated using a time-based weighting scheme. The residual error of participants with higher body fat percentages was greater by 30% when compared to residual error of participants of lower body fat percentages. Additionally, time-based weighting scheme reduced residual error by 20% on average compared to constant-value weighting scheme. Our results indicate that multibody kinematic optimisation methods are adversely affected by higher body fat percentages and that time-based weighting can provide higher fidelity movement analysis irrespective of body fat percentages. Through our results we aim to develop tools which provide greater precision in obesity-related movement analysis. Such tools could also help address the disparities in rates of obesity associated with different ethnic or socioeconomic background. ### Competing Interest Statement The authors have declared no competing interest.