The Competitive Image photographers captured this great still shot of Big Matty Reed doing a flying dismount. I've posted other video links of the flying dismount, but this is a good look at how the rear leg is set-up. Matty has swung his leg over the back of his bike and it is in position to make contact with the ground. He is moving fast (not sure of the mph) so he can literally hit the ground running.
The next photo in the series is Andy Potts in near the same postion, just a bit later. Too bad you can't see his feet, but I suspect his foot is touching the ground in this photo.