simtk.org

Hi all, thank you so much for your work on this model. I have been reviewing some of the forum posts and wanted to seek any input on potential implementation of this model for forward dynamics simulations.

I am hoping to run some forward dynamics/contact-based simulations with a focus on the spinal model and spinal loading. Would you have any advice on which muscles or components I might be able to remove/restrict/modify to be more appropriate for a forward dynamics-based approach? I saw in some of the forum posts that this model hasn't been used for forward sims but figured i'd ask any and all for advice.

-Brandon

Brandon,
Thank you for your interest in this model and kind words.

As for forward simulations, you are correct, we are unaware of anything published using this model. Since I left the Anderson Lab I do know that he worked with another student on something in MOCO, but unsure how far that got or if they ever got anything working. So, I really don't know what to tell you.

I have a little experience with the basics of forward simulations etc. (from my time at UMass and taking courses from Dr. Brian Umberger) and appreciate the challenges this many MTAs presents (and I have toyed with the idea of trying get it to work with this model). My inclination would be (in no order):
- try throwing CPU hours at it. If you have confidence in your abilities and have access to a Super Computer, see what it can do.
- Consider trying to consolidate segregated MTAs of similar function (~what you suggest)
- Consider just making a torque driven model then applying the kinematics to a model with MTAs. Knowing that you would ideally model the joint torques based off from their potential. This would ignore biarticular functions, but still should be a ~decent representation of things.
- Use a more basic gait model with a single rigid body for the trunk (or one with 1-2 joints), and then apply the kinematics of that model to this one. Or maybe try the Beaucage-Gaveraue lumbar model (or my SOpt model, which is basically the same thing), as it is 1/3 the complexity.

Clearly all these suggestions have limitations, but just spit balling. But I think it should be possible if you know what you are doing. I just wouldn't start out with this model, get confident doing forward sims with a simpler model and try adding levels of complexity. Otherwise, I'll still a quote from Einstein:
"... models should be as simple as possible, but not simpler than that".

Let me know if you have any ideas you want to bounce off etc. Sorry I can't be of more assistance than that.
Jake Banks