Is this a tracking or forward simulation? If it's tracking, it could be helpful to find out what joint torques are needed for the given motion (for both with and without an AFO) to find out if there are additional joint torque requirements that might be driving changes in the muscle forces.

An external force does not always need to be applied to bodies that interact with the ground. Many people use simulations for gait, so this is often what is done, but if a force interacts with the upper body, it makes sense to apply it to the correct body (e.g., upper arm, arm, hand).

This error message is indeed a bit cryptic and misleading. With the newer versions of MATLAB, there are now two versions of MATLAB for Mac (Intel and Apple Silicon). OpenSim 4.5 only has libraries that work with the Intel installation, so make sure to use that version of MATLAB. Even though your lap...

Dylan and Sanghee,

We put the failed trials back into the queue and looks like they worked this time.

The documentation pages for the Overview of OpenSim Workflows and the Examples and Tutorials would be great places to start to find what could work well for your use case.

Apologies for the issues. We believe the login issue should be resolved now.

Which residual is reaching < 9000N? In the screenshot there are some large FY values (>200 N). This might point out that there is an issue with the external forces you are applying to the model (either in magnitude or location or both). One way to check is to run Inverse Dynamics and see if reasonab...

There are some extra options with IK that you can use by editing an existing setup. You can create the setup file from the GUI by saving the settings, and then you can open up the setup file in a text editor (such as Notepad++). One helpful way to see all the tags is the XML Browser (in the GUI, Hel...

As long as you can get the external force/moment and the point at which the force is applied, this should work. For your canes, it seems like it should give you the force and point applied (with the markers). One question is whether the canes can generate a moment (something similar to the free mome...

There are a few options for how to do this. The Overview of OpenSim Workflows is a great place to start to see what might be best for your specific research question: https://opensimconfluence.atlassian.net ... +Workflows