Muscle morph animation

My first animation (yay). I was trying to create a step-by-step for my morphing method, to answer a deluge of questions I was getting about it (well, two questions, but they were worded real nice). Anyway, couldn't come up with a decent method, so I went for an animated gif, which I think best demonstrates what it is I'm doing.
Click the download button to play the animation.

The original is a picture of GoDaddy spokesperson (and, apparently, WWE diva) Candice Michele, taken from Muscular Development magazine.