Rectus femoris (biarticular muscle) in Static Optimization

[Hoon Kim]

Hello.

I am conducting a research to compare the muscle forces between weight lifting exercises such as squat.
I am using the new squat model (https://simtk.org/projects/high-hip-flex).
I found my simulated activation in the Rectus Femoris was not activated (or little activated) during squat motions.
Other muscles such as Vastus lateral, intermedius, and medialis were reasonably activated during the motion. Vastus muscles produces 99% of quadriceps muscle forces from Static Optimization during the motion.
Could you get me some suggestions to run Static optimization in which I can get reasonable activation in the Rectus Femoris muscle?
Thank you so much for any comments.
Have a nice day

Sincerely,

Hoon

[Thomas Uchida]

Have you checked the rectus femoris fiber length?