How can I get the muscle tendon length with respect to a certain joint angle?

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XiaoDong Liu
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Joined: Wed Mar 29, 2023 6:06 pm

How can I get the muscle tendon length with respect to a certain joint angle?

Post by XiaoDong Liu » Fri May 05, 2023 12:46 am

Hello~ I have some questions about the calculation of muscle tendon length.

As I tried before, I found that there was a significant linear relationship between the muscle tendon length and the corresponding joint angle. I want to know how the opensim calculate the muscle tendon length given the joint angle. I found some APIs, such as getFiberLength() and getFiberLengthAlongTendon(), but I cannot find the code of these APIs and cannot find out the principles about these calculation. :?: It confused me a lot. So could you please answer my questions? :D

Thank you from the bottom of my heart! :P
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Windows
GUI
OpenSim 4.1
MATLAB
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Thomas Uchida
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Joined: Wed May 16, 2012 11:40 am

Re: How can I get the muscle tendon length with respect to a certain joint angle?

Post by Thomas Uchida » Fri May 05, 2023 3:57 am

The length of a muscle-tendon unit is defined by a path (these are the red cylinders you see in the GUI). The path length is distributed between the fiber and tendon such that the fiber and tendon are in equilibrium. You can find details in the "Muscle Model Theory and Publications" section of the documentation (https://simtk-confluence.stanford.edu:8 ... blications) and in the papers that are referenced there.
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