Optimization of via points: bridging the gap between simulationspeed and biological fidelity of musculoskeletal models

When designing musculoskeletal models for forwardsimulation studies, a tradeoff must be made between biologicalfidelity and computational efficiency. A method is proposedthat optimizes the coordinates of via points of muscle paths,used in relatively simple musculoskeletal models, such that themuscle moment arms match those of more complex modelsand experimentally measured moment arms. For this purpose,the via points of the Gait2392 model are optimized to matchmuscle moment arms of the Rajagopal2015 model and otherexperimentally obtained muscle moment arms. The results showthat muscles that can be represented by straight lines, can beoptimized well. More complex muscles that contribute to multi-degree of freedom movements, are still improved, but to aless extent. The main benefit of the optimized model, is thatthe compatution time of human motion simulation is greatlyimproved, making it a viable option to pre-train neuromuscularcontrollers, which can be further fine-tuned with the morecomplex models. To further improve musculoskeletal models ingeneral, more data on muscle moment arms is needed, especiallyfor muscles that contribute to multiple joints and movements inmultiple planes of motion