Sitting Down? That's the whole concept behind RHIP, it's way easier doing a 15k'er sitting than it is on ones own feet.
The Corps calls it their 'Crucible', and the Army has hammered it to 'Victory Forge'
http://usmilitary.about.com/od/joini...rusmcbasic.htm
I could think of a few other things that would begin to aile if one were to sit that long!