Okay, I was reading a lot of things in the comments section about the Prior-Tejada deal and some things stuck out at me as not being really correct.

1. Dr. James Andrews and the American Sports Medicine Institute (Kevin Wilk) is the ONLY authority that has the real authority on pitching mechanics.  I only say this because I know they have over a thousand pitchers on video and they are now going over the data to determine what might be better to prevent injuries. I have had four different lectures on pitching mechanics and they have all said different things.
2. The idea that Prior uses a lot of legs is really false.  Look at him again sometime.  He has big calf muscles, but he has little thighs and more importantly little butt muscles (hip extensor strentgh).  One of the more important things I have learned is you have to have a proper balance point on your right leg as you pivot and turn to home.  That has to be balanced on a single leg, and you have to have good strength throughout the right leg in order for the arm to function properly.
3. Finally, your whole body provides the power, not just the shoulder or the elbow.  One of the physical therapists talked to us about Ben Sheets and how he worked mainly abdominals with him one off-season.  Those are just important as any shoulder muscle.

I am by no mean an expert on any of this stuff. It's very complicated, but the things above is stuff that I picked up on in my training in school.