Here is a rig I have been working on for a project lately, using “stretch to” constraints to simulate the muscle stretching and contracting. You may download a BLEND file of the base rig here (still needs to be further set-up and tweaked fully, bones need to be named as well as sized properly). I don’t mind if anybody uses the rig but please give me credit if you decide to use it. I’m still looking for better solutions for some things, the feet for example.
Now when I tried to parent the armature to a model I was not able to make it deform the mesh. I tried envelopes (I scaled up the radius) and vertex weights but I just don’t seem to be able to make any model deform with that rig. I then built another less complex armature for that project which works fine. Oh, and I should mention that I’m working on this in 2.4 RC1, since I saved in there I can’t open the file in 2.37. I’ve build parts of the rig separately in 2.37 (an arm for example), and that works fine too.
Help and suggestions are very much appreciated!