Extracting simulation data after inverse kinematics

[Vidhey Oza]

I have motion capture data on which I run inverse kinematics to get the associated joint angles. Now I want to extract muscle activations from the resulting simulation but I can't find any way to do so either on the GUI or on the Python API.

I'm fairly new to OpenSim so I got a bit overwhelmed by the documentation and couldn't find the answer to this. Could someone guide me through the same? Doing this through Python API is preferable to maintain the flow of my project.

[Thomas Uchida]

I run inverse kinematics to get the associated joint angles. Now I want to extract muscle activations from the resulting simulation

Kinematics is the study of motion without consideration of the forces involved. If you want to compute muscle forces, you will need to perform further calculations (e.g., using the Static Optimization or Computed Muscle Control tools in OpenSim). The "Overview of the OpenSim Workflow" page in the User's Guide might help you get oriented (https://simtk-confluence.stanford.edu/d ... m+Workflow).

[Vidhey Oza]

Thank you for the clarification.

There are functions in the API like getActivation and getTendonStrain. I was under the impression that these should be able to return the values I need, but they always seem to have a constant value.

About your suggestion to use Static Optimization or Computed Muscle Control, I mainly only have access to motion capture data, I feel Static Optimization is the way I will be able to work. In the documentation, it says it also requires data for external loads. Is there a mechanism to be able to record such data?