Hello, you want to use the defult function from Thelen muscle or introduce your own function for active force calculations? If the firs one,I've added document about Thelen muscle where you can find the active force equation. If the second, you need to look into "OpenSim Developper Guide" and check ...

Btw. Passive forces are not included into muscles during Static Optimization simulations.

Hello!

But you have already read the "Users Guide" did you?

Hello once again! Passive force is related to the maximum isometric force so if you want to increase maximal active force that muscle can generate and in the same time don't change the passive forces you need to change the passive force shape factor value. You can also change optimal fibre lengths i...

Hello! Muscle ability of producing active force is related with its optimal fibre length. Propably muscles that you are yousing possess too big optimal fibre length compared to maximal length that they can achieve during simulation. Zajac in his work writes that each muscle length in maximal positio...

That is a good question. In all muscle models the passive force is in some way related with maximum isometric force. We can considere that muscles of person who is training are stronger than a normal person, maximum isometric force is related with number of sacromeres that can be activated so when s...

Hello again! I'm having the same problem as you but with CMC, I have calculated the forces produced by residual actuators and compared with the sum of forces produced by muscles and it turned out that there is some kind of unnecessary activation of actuators which provokes maximum activations in the...

Hello!

What do you mean by changing muscle length? Changing the optimal fiber length value and tendon slack length value?

Hello!
Static Optimization tool does not take into account muscles passive forces, but CMC does.

Hello, yes I have the passive forces that occurs in muscles when they have maximal length, I think that default value is equal 4 since the muscle is scaled for gait model, you can look in this Millard publication when he presents his model based on experimental results and you can observe that the p...