Varying muscle activation and forces.

[Yong Cho]

Hello, I ran a static optimization on a upper arm extremity model after applying a constant force. When I saw the results, I couldn't understand it. I was under the impression that a constant force would result in a constant activation for a specific muscle but the results showed that muscle activation for a muscle was varying while others were constant. Can someone explain why this is happening or if I'm just doing the simulation wrong.

[Thomas Uchida]

Is the model moving or are all joints locked?

[Yong Cho]

Everything is locked

[Thomas Uchida]

If the model is not moving in the motion you're tracking and the external force is constant over time, then each time frame should look the same and Static should return activations that do not change with time. Do you get constant activations when the external force is absent?

[Yong Cho]

Thank you for replying, it's fixed now.