Simulation of hemiparetic gait

[Emeline Debalme]

Hi Thomas,
I am currently working on simulating a hemiparetic gait by reducing the range of motion of the right hip joint, while keeping the left side unaffected. However, the results I'm obtaining from the simulations show a symmetric gait pattern between both legs, which is unexpected.

I thought of two possible explanations for this outcome: either the optimized gait found by the simulation favors a symmetric solution, or there are parameters in my model that are explicitly enforcing symmetry. Based on my research, I discovered that the "symmetric" parameter in the controller file is set to 1. After changing it to 0, I have already observed noticeable differences between the two legs, even with small impairment levels.
Do you think that the symmetry issue I encounter could indeed be due to this "symmetric" parameter in the controller? Or could there be other factors in the model that might be enforcing symmetric behavior?

Additionally, I would like your advice on the best approach to reduce the range of motion: should I modify the hip joint ROM directly in the model file, or would it be more effective to adjust it through the measures file?

Thank you for your help!

[Thomas Geijtenbeek]

I suspect that the reduction of the range of motion is not enforced correctly. The best approach in your case is to enforce the range reduction in the model itself, since it is a limitation and not a preference.

In OpenSim, you would need to add a CoordinateLimitForce to reduce the range of motion, while in Hyfydy you would need to adjust the "limits" property for the hip_r joint.

You also correctly noted that the "symmetric" parameter should be set to 0 to allow for asymmetric control.

[Emeline Debalme]

Hi Thomas,

Thank you a lot for your answer!
Have a nice day.