Stiffness analysis of crank motion task using musculoskeletal model with six muscles

It is important to clarify that how are the stiffness and the torque of human arm controlled in the interaction with the environment. Traditionally, the stiffness of human arm has been measured by adding perturbation. However, it is difficult to measure the stiffness in isotonic movements with various loads, because the perturbation provides the unexpected stiffness increase by antagonistic muscles. In this paper, the musculoskeletal model with six muscles is used to estimate the joint torque and stiffness in crank rotation tasks. The parameters of the model are estimated by experiments. And the pre-programmed reaction for the predictable load torque are evaluated.