Are upper body muscles represented in the BSM?

[Arish2022]

Hi everyone,

I'm trying to determine whether any specific muscles from the upper body are represented or mapped within the BSM in OpenSim. I’ve reviewed the documentation but haven’t found detailed information on this.

From what I can see in the attached image showing the BSM in OpenSim, only the lower body muscles seem to be visible. Does anyone know if muscles like the pectorals, deltoids, or trapezius are included in the upper body section? If so, how are they represented or modeled? Any references or further clarification would be greatly appreciated!

Thanks in advance!
Arash

[MarilynKeller]

First, note that the BSM model is only supported by Nimblephysics so far. A difference of implementation in the scapulo-thoracic joint in OpenSim causes the weird shoulders pose you captured.

This issue is tracked here: #10

For the upper body muscles, I suggest you check the definitions in the bsm.xml file directly. To build BSM, we merged in the upper body from Ajay Seth (https://simtk.org/projects/scapulothoracic), I a not sure whether it had muscle definitions.

[Arish2022]

Hi @MarilynKeller,

Thank you for your insights.

I’ve been revisiting your comments from February about creating the BSM model as an .osim XML file, which was then parsed with NimblePhysics (reference). I was wondering if the current BSM file is after parsing by NimblePhysics. If so, would it be possible for you to share the original file prior to parsing?

Additionally, I created a new Ellipsoid joint in OpenSim and compared it with the scapulothoracic_l Ellipsoid joint in the BSM model. The formats aligned, with the only notable difference being the negative radii values, as previously noted in this reference. Could you review the BSM file to ensure this isn’t a typo? Notably, the radii values for scapulothoracic_r are positive.

Thanks again for your guidance!

Best
Arash