Hello and good day to all,
I had a couple of questions about the two element muscle model (the class
AnyMuscleMODEL2ELin). Specifically my question is related to the tutorial and what the tutorial says for how the two element model takes into account passive muscle forces. In the muscle modeling tutorial, the following three sentences are present:
“This is passive elasticity. The two-element muscle model of the preceding section handles the presence of this elasticity by increasing the strength of the muscle, and this works fine if the muscle is supposed to be active in the sense that the model in such a state would predict a high force with a low muscle activity. But the passive muscle force cannot be switched off, so it will still be present even if it is disadvantageous, and the two-element model will not predict this.”
I have two questions about this statement. The first is what does the tutorial mean when it says that the two element model accounts for passive forces by increasing the strength of the model? Is there some function of passive force related to the length of the muscle which computes maximum possible force and adds that to the strength of the muscles? Could it be some constant value that is added to the strength regardless of muscle length?
The second question is with regards to the last statement “But the passive muscle force cannot be switched off, so it will still be present even if it is disadvantageous, and the two-element model will not predict this”. Could someone explain how it’s even possible to switch off passive force? I thought passive force was related to the length of the muscle such that it is either present or not. If the length of the muscle is a certain value, there is going to be a passive force associated with that. Maybe the answer to the first question will help with my second one.
Thanks for the help,