About the arm26 model simulation

[fujibe kenshun]

Dear all

I want to simulate an arm26 model in Matlab. However, there are two things I do not understand in doing so.
The first is the conditions under which the muscles wrap around the shoulder and elbow joints when deriving the muscle length function.
The second is the function after the muscles are wrapped around the shoulder and elbow joints.

Additionally, I found a video of the arm26 model being simulated in Matlab, is there a program for that?

Best regards