Scaling subject-specific muscle strength

[João André]

When making musculoskeletal models subject-specific, we understand that Opensim offers some methods to scale the model (https://simtk-confluence.stanford.edu/d ... im/Scaling) regarding body dimensions and muscle fiber lengths. However, as https://simtk-confluence.stanford.edu/d ... ing+Worksm - step 4 warns, "Muscle strengths are not scaled during the scaling process, and any updates must also be made by the user". Considering we are currently working on a project that is fairly sensible to these muscle strenghts, we are looking for a practical way to scale them as well.
Is anyone familiar with methods to scale maximum muscle strength or has a recommendation of a specific procedure to follow? We are most interested in a method capable to scale muscle strength using EMG.
The literature regarding this subject points out some methods to scale muscle strength, namely the mass-length law (https://linkinghub.elsevier.com/retriev ... 9011005847) or the method by Hayashibe (https://hal-lirmm.ccsd.cnrs.fr/lirmm-00637754). Is anyone familiar with these methods or has a recommendation of a different procedure to follow?

[John Davis]

I can't speak to scaling from EMG data, but I've had success using height and mass to scale the strength of the muscles in my lower-body models using the regression equations from Handsfield et al. 2014. There's a separate equation for each of the major lower body muscles in the supplementary material in that paper.

I just uploaded my MATLAB script that implements this method via the OpenSim API to my GitHub here if you'd like to use or modify it. I made this code specifically for models derived from the Rajagopal 2016 model, so it'll need some tweaks for other uses, but should give you something to start with. Hope this helps!

[Najoua Assila]

Hi,

Using the EMG data, there is the CEINMS toolbox (https://simtk.org/projects/ceinms) that calibrates musculo-tendon parameters including the muscle max isometric force.

Hope it helps,

Najoua

[Mohammadreza Rezaie]

Hi,

This project might be of your interest:
https://simtk.org/projects/opt_muscle_par/

Best,
Mohammadreza