Interpreting Musculoskeletal Models and Dynamic Simulations: Causes and Effects of Differences Between Models

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Human gait analysis

Background:

• OpenSim is widely used for musculoskeletal modeling, with numerous models available for gait studies.
• Understanding how different model parameters influence gait mechanics and muscle function estimates is crucial but not fully elucidated.

Purpose of the Study:

• To investigate the impact of four distinct OpenSim models (Gait2392, LLM 2010, FBOM, FBM 2016) on gait mechanics.
• To assess how these models affect estimations of muscle forces and activations during human walking.

Main Methods:

• Six healthy young adults were scaled within each of the four OpenSim models using identical experimental gait data.
• Gait kinematics were reproduced, and static optimization was employed to estimate muscle function across all models.
• Simulations were performed using OpenSim 3.1.

Main Results:

• Significant differences were observed in simulated joint kinematics, moments, and muscle function (forces, activations) between models.
• Peak differences included up to 6.5° knee range of motion and 462 N peak rectus femoris force.
• Increased model complexity correlated with greater discrepancies between simulated and experimental measures.

Conclusions:

• The Gait2392 model is deemed sufficient for studying walking biomechanics in healthy young adults due to its accuracy and lower error.
• Differences in coordinate systems and muscle parameters between models significantly influence results.
• Further research is recommended to identify optimal models for more complex movement tasks.