Similarities and differences between musculoskeletal simulations of OpenSim and AnyBody modeling system

Abstract

Human musculoskeletal models have revealed the general patterns of muscle recruitment during daily activities. Nonetheless, the consistency of dynamics calculations from different musculoskeletal simulation packages is not well understood. The objective of this study was to understand the effect of the simulation solver and simulation model on the musculoskeletal simulation results using lower limb models in OpenSim and AnyBody modeling system. Matched musculoskeletal model and generic model in both systems were simulated using the external forces and joint kinematics measured at the Fourth and Sixth Grand Challenge Competitions to Predict In-Vivo Knee Loads. Muscle activation levels in lower limb were compared between the packages, and against the electromyography signals from the aforementioned competitions. The muscle activation levels were very similar between the two packages when matched models were simulated, indicating high consistency between the solvers. In the generic models, the root mean square (RMS) difference in the muscle activation levels was high at 0.15 and 0.19 for ideal force generator muscles and modified Hill-type muscles, respectively. The RMS and phase differences were high between the muscle activations and electromyography signals. Comparisons will help understand the similarities and differences between the musculoskeletal simulation packages and the effects of the model differences on simulation results.