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Hello,
I want to simulate forward dynamics that transform muscle activation to muscle force by Hill-type model. But I dont know how to determine the muscle force-length curve and force-velocity curve of my subjects' muscle. Are there any methods to get these model parameters that match my subjects?
Any help is appreciate.
Thanks
Bo Ding

Hi, I had the similar problem which you have and I did not found any step in OpenSim that return the muscle relationships like force-length and force-velocity.
However my solution was to implement both functions, as it is suggest in the following papers:

Rosen J, Fuchs MB, Arcan M. (1999). Performances of hill-type and neural network muscle models toward a myosignal-based exoskeleton. Computers and biomedical research.

Kaufman KR, An KNW, Litchy WJ, Chao EY. (1991). Physiological prediction of muscle forces–I. Theoretical formulation. Neuroscience.

I hope it helps you.

Regards,

Emiliano Ravera.

Hi Emiliano Ravera,


Thanks for your reply. What does "implement both functions" mean. My question is how to determine the parameters of hill model equation such as max-isometric-force etc. Did you just use these parameters from other literatures or measure these paramenters from your subjects in experiments?

Kind regards,


Bo Ding

Hi,
I am new to the subject but as I know so far, it depends on what you wanna do. Usually it's a good approach to take the average values of the parameters. For example, here http://www.wheelessonline.com/ortho/muscle_index you may find them.

Hi Bo Ding,
When I said "implement both functions", I mean that both functions have to be made in MatLab. These functions depend on muscle length and shortening muscle velocity, and you can find these parameters into state file of CMC algorithm.
On other hand, to estimate morphological muscles parameters involved in the Hill model such as PCSA and maximal muscle stress, I use others papers.

For example, for PCSA I use the following paper:
Horsman et al. (2007). Morphological muscle and joint parameters for musculoskeletal modelling of the lower extremity. Clinical Biomechanics.

But, a large range of values for the maximal muscle stress was reported in the literature, an example of this value can be found in page 3 of this paper:
Prilutsky and Zatsiorsky. (2002). Optimization-based models of muscle coordination. Exercise and Sport Sciences Reviews.

I hope that it help you.

Regards,

E. Ravera

Hi all,

You can plot the muscle force-length and force-velocity (fLfV) curves in the GUI. The example for this can be found here; http://simtk-confluence.stanford.edu:80 ... er+Surgery

Changing the muscle strengths can be done either in the gui or directly in the .osim file.

The question of matching the models strength to your subjects is difficult. If you haven't collected any data to calibrate your model you will have to scale based on literature that correlates age/gender/mass/height with muscle mass or strength.

There currently isn't functionality in OpenSim to do that for you. You will have to develop your own methods for estimating the subject specific muscle properties.

Cheers,
-James

Hi all,
Thanks for your replies. I have another question. If i have obtained the muscle force-length and force-velocity curves then i can use the Hill equation to calculate muscle force. My question is how to determine the input of the equation such as the fiber length of every instant? I don't understand how Opensim apply the Hill type to calculate muscle force.
Thanks
Bo Ding