Saul & Murray upper extremity model for dynamic tasks?

[Samuel Hybois]

Hi everyone,

I am currently using various musculoskeletal models to describe the manual wheelchair locomotion task.

When using the upper extremity dynamic model (Saul & Murray, https://simtk.org/projects/upexdyn) I get unrealistic values from inverse dynamics for shoulder moments (which I don't get when computing with other models, with the same raw data). It makes me wonder if this model, with regression equations and coupled coordinates constraints, is suitable for dynamic tasks in the sagittal plane ?

Has anyone used this model for other kinds of activities and experienced similar issues?

Thanks for your help!

Sam

[Dimitar Stanev]

Hi,

The developers of the model used it in a forward dynamics manner (e.g. CMC). I think that OpenSim's inverse dynamics do not account for the constraints, because a particular recorded movement may violate them, thus they are ignored. I would suggest you to perform a forward dynamics simulation and compare the driving forces to the corresponding forces computed from inverse dynamics to verify this.

Best

[Kristy Godoy]

Hi Samuel.
Did you get to know why Saul & Murray upper extremity model gave those unrealistic results on the shoulder?
I'm having the same issue. I have been looking for a way to go around and get other results but nothing works.
I appreciate any updates.

Thank you.