How to check passive muscle forces?

[Daniel Pina]

Greetings,

I've been advised to check the passive muscle forces in my model.
How do I observe this factor? Running Static Optimization I get "muscle force" and "muscle activation" files. How do I distinguish passive forces from active/controlled forces?


Thank you for your help!

[Thomas Uchida]

I've been advised to check the passive muscle forces in my model.

You can attach a MuscleAnalysis to report such quantities. https://simtk.org/api_docs/opensim/api_ ... lysis.html

[Daniel Pina]

Hello,

I can't find a way to attach the MuscleAnalysis to SO using the GUI.
Is it possible to just run "Analyse" and activate "MuscleAnalysis" while using the SO output as controls and the motion file that I used in SO?

Here's the description:

Analysis_After_SO.png (35.85 KiB) Viewed 1901 times

[Adrian Lai]

To my knowledge, I don't believe static optimisation include the passive force-length curve of the muscle fibre so what you're predicting using static optimisation is active fibre force only.

Hope that helps!

[Daniel Pina]

Hello Adrian and thank you for your input!

The subject of the passive forces came up in a question I put in another thread where I ran Static Optimization only:

viewtopicPhpbb.php?f=91&t=8081&p=0&start=0&view=


Regardless, in the Analysis tool I'm only using the muscle controls from the SO's output, but I could just use RRA's instead, because the all I'm trying to evaluate are the passive fiber forces anyway.