Rigid-body and musculoskeletal models

In this chapter, we will look into rigid-body and musculoskeletal modeling. With these models, it is possible to estimate muscle, ligament, and joint forces that are typically difficult, or even impossible, to measure directly within the human body. Therefore, the only viable option is to estimate these, and this is what rigid-body and musculoskeletal models enable. We will introduce the fundamentals of rigid-body and musculoskeletal modeling and use it to analyze a simplified model of a human on a bicycle. We will show how we can alter the musculoskeletal models by altering the design of the bicycle. Lastly, we will briefly describe other applications of rigid-body and musculoskeletal models such as (1) how they form a basis for understanding quantities we cannot measure directly, (2) enable investigations that are impossible to perform experimentally, (3) can provide boundary conditions for detailed joint models, and (4) how the models can be applied for design optimization of equipment that interacts with the human body.