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I am learning about the use of OpenSim, I am using the FBLS model of Raabe to calculate intradiscal forces in sitting position through small variations of inclination of a seat, and I want to know if OpenSim allows making the following consecutive steps in the following order and if it is the correct way to do it?

1. kinematic calculation using the Forward Dynamics tool considering the contact forces of several elements.
2. Calculate the actuators by means of the Static Optimization tool.
3. Finally, make an analysis of forces using the Forward Dynamics tool.

Cordially,

Luis Ortiz.

Hello,

Expanding the previous information.

In the configured model there are contact surfaces and contact forces between the human body and a seat, we do not have kinematics previously defined by experimental methods and we want to find the accommodation of the body in order to do a static optimization and finally calculate the joint reactions. That is to say, we have the model in a static seated position previously configured, without any movement, for that position can we calculate the reaction joint forces?

cordially,

Luis Ortiz

If you don't have neither kinematics nor externally applied forces the problem is very difficult to solve. It is possible but you will run into multiple problems.

You can try to use forward dynamics (FD) to predict the movement and contact forces between the seat and the model. However, you have to tie the model to avoid funny behaviors and unreasonable contact forces. Then you can apply the contact forces to the model, assuming a static pose, and calculate the muscle forces and joint reactions.

Dear Dimitar.

Thank you very much, we will try to do it that way, any doubt will bother you.

Cordially,
Luis Ortiz