they are pretty much the same except that in one i used the spline ik solver and in the other they are only 2 bones the main bone and the nub.
the way i made this is very simple.
i dont knowif someone has posted something like this in the thread since this is my first post here i thought it should be a good one so here is how you go on making this.
first draw out the first 2 bones making your first bone your muscle and apply a turbosmooth and a taper and change it to red (just to look nice).
create 2 point helpers and align them to each pivote of the bones.(one for each bone).
now position constraint the nub to the helper on its pivote.
(you can move the helper around and the top bone will scale up or down but wont follow).
now select the first bome (muscle) and do a look at constraint to the point helper on the tip, after that you can select the muscle and link it to the top helper and then you have the muscle ready.
the stretchy bones is the same method but you have to start with a spline ik base and leave as default the helper number when you finish the *spine* cause it will give you a helper on the pivot of every bone and just position constraint and look at constraints like the muscle setup.
here are the files (http://www.geocities.com/ifarca/stretchy_bones.zip)