simtk.org

Hello,

I am using the Arm26 model to simulate a curl while holding a dumbbell. I have taken .trc files from Vicon Motion Capture Lab while doing the exercise and have successfully completed the scaling and Inverse Kinematics. However, I am having trouble computing the muscle forces. I have been using the Analyze tool to apply an external force to the model and to calculate muscle forces using the Actuators analyses. I am getting a huge value (around 250 N) for the muscle force of the long Tricep. While my BIClong and BICshort are only around 70 N. Does anybody have any suggestions to why this is happening?

Thank you,
Matt

Hi Matt,

The analyze tool isn't designed to do what you are using it for. The tool is designed to take a set of states that have been calculated elsewhere and use those states (and the model) to analyze the system. It doesnt't work very well when you are getting the tool to run the simulations. We are going to try and resolve this in upcoming releases.

You can either calculate an external load, or increase the mass of the hand. Then run static optimization and/or CMC. Once done, you can use the output states to do an analysis.

Let us know if that helps,
-james