Rigging an anatomical muscle Is there a way to make a rig that keeps my muscle attachments firmly anchored onto two separate (anatomical) bones while the arm bone moves?
I want to show a few muscles moving with the shoulder joint but I can't find any similar examples on the internet other than muslce approximations that make flesh bulge. Here I don't need skin. 

The goal is to show muscle transfer surgery - how relocating a nearby muscle can bring back movement lost with paralysis after injury. For example, sometimes a portion of the pec major is transferred on top of a paralyzed deltoid muscle. If anyone has any ideas for potential rigging workflows that might allow me to rig an anatomical muscle in this way, please share ideas I might research. I am working with retopologized versions for actual rig tests.

I have been trying to use hook modifiers, but they seem to stop working sometimes.  

Thanks!
Jim
I think I have solved the problem of the hook modifier behavior by making custom vertex group hooks. I copied the vert group and assigned it but also made an exact copy as a separate mini-mesh. 
The shiny torus was manipulated with the hook technique I came up with today. If anyone else has trouble with hook behavior, perhaps I should upload the screen shots.
FYI the custom vert/hook objects are invisible on the torus but I parented them to the cylinders. I will try on real bones later.