Total fiber force is Nan value

[Arash Mohammadzadeh Gonabadi]

Hello all,

I have a question about the active, passive and total fiber force.

When I run the muscle analysis to get the total fiber force, I have noticed the values are NaN; while the active and passive fiber forces have values (actual values).

If I understand correctly:
=> total force = active fiber force + passive fiber force

I have put the files in the following address:

https://unomaha.box.com/s/f03jfo64sxbn5 ... aoocks3u0o

I do not what is wrong with the model. I will appreciate if someone could help me.
Thank you in advance.

Best,
Arash

[Thomas Uchida]

You are using the Schutte1993Muscle_Deprecated muscle model. "Deprecated" means that it is no longer supported and it may not be thoroughly tested with all the latest infrastructure. The deprecated model may not have been upgraded to the latest API and may not be populating the "activeFiberForce" entry of the "MuscleDynamicsInfo" struct. You might consider using a different model, or upgrading your current model to use a supported muscle.

[Arash Mohammadzadeh Gonabadi]

Thank you so much for responding.

The model that I have used is (Lower Limb Model 2010):
https://simtk-confluence.stanford.edu:8 ... Model+2010

From this article (Muscle-tendon mechanics explain unexpected effects of exoskeleton assistance on metabolic rate during walking):
https://www.ncbi.nlm.nih.gov/pubmed/28341663

Do you think by this current model, if I use active+passive fiber force, can I reach the total fiber force?
Or the active and passive fiber force could be wrong as well?




Also, I have another question.
=> When I run this model in OpenSim 3.3 (GUI) and extract the IK results, everything seems good (the units).
=> But, When I run this model in OpenSim 4.0 (GUI) and extract the IK results, I noticed that there are some minor inconsistencies with the model. For example, it appears that the joint angle and joint angular velocity for the left hip and right knee are stored in degrees, and the right hip and the left knee is in radians.

Thank you so much.

Arash

[Thomas Uchida]

Or the active and passive fiber force could be wrong as well?

It depends what you mean by "wrong". You should always confirm that the model you are using is appropriate for your study. If you're wondering whether the muscle model returns different answers between OpenSim 3.3 and 4.0, you might try running a simple test (e.g., tug-of-war simulation) and comparing the results. However, unless you have a good reason not to, I suggest using a newer model like Rajagopal's. Please see the paper for details about the model and improvements from older models:

Rajagopal, A., Dembia, C.L., DeMers, M.S., Delp, D.D., Hicks, J.L., Delp, S.L. Full body musculoskeletal model for muscle-driven simulation of human gait. IEEE Transactions on Biomedical Engineering, Vol. 63 (9), 2016. https://nmbl.stanford.edu/wp-content/up ... al2016.pdf

[Arash Mohammadzadeh Gonabadi]

Thanks a lot, Thomas.
It was really helpful. I really do appreciate your consideration and help.

Best,
Arash