simtk.org

Hi every body,
I am working on opensim to compute muscle forces during motion but I am not able to get the x,y,z components of the force (i.e. the direction of the muscle force at any frame of the motion). For example I want to know the direction of force for all muscle acting on Knee joint at any angle (0, 30, 60...) of knee flexion during gait cycle. Any one can help me in this.
Thanks
Sultan

Hi Sultan,

The analysis you need for this is not built into OpenSim, off-the-shelf, however you can write a plugin to compute these lines of action and report them in whatever format you want. It's a little bit complicated to report since some muscles have variable number of segments, so you may want to keep this in mind. If you decide to go this route, you'll need to write either a Plugin or a main program to compute these line of action using the API (requires C++ programming). I'm sure the community would benefit a lot from such contribution (we have many users distributing their plugins on simtk.org).

Please let me know if you need help proceeding in this direction.

Best regards,
-Ayman

Dear Sultan,

my research group has recently developed an OpenSim plugin that can extract muscle lines of action for a certain kinematics. It is not a public plugin yet as we want to add some other features before the release, but if you are interested in testing it, please send me a private message.

Best regards,

Luca