Prescribing joint co-ordinates during model preparation in OpenSim improves lower limb unplanned sidestepping kinematics

Objectives Investigate how prescribing participant-specific joint co-ordinates during model preparation influences the measurement agreement of inverse kinematic (IK) derived unplanned sidestepping (UnSS) lower limb kinematics in OpenSim comparison to an established direct (DK) model. Design Parallel forms repeatability. Methods The UnSS 20 elite female athletes were calculated using: 1) DK (criterion) and, 2) two IK models; one with (IKPC) and without (IK0) prescribed marker registration phase OpenSim. Time-varying analyses performed using dimensional (1D) statistical parametric mapping (α = 0.05), where zero (0D) Root Mean Squared Error (RMSE) estimates used as a surrogate effect size estimates. Results Statistical differences observed between IKPC well IK0 kinematics. For models, mean over stance for three (3D) hip joint, 3D knee ankle flexion/extension (F/E) degrees freedom (DoF) 46 ± 40% (RMSE 5 5°), 56 31% 7 4°) 3% 2°) respectively. F/E DoF 70 53% 14 11°), 48% 8 7°) 100% 11°) Conclusions Prescribing improves model, previously published in-vivo