Can't imagine hitting jumps like that on a bmx bike. I'd hit jumps three times as big on a dirt bike, but at least I have suspension. I have no idea how they find the pedals after doing tailwhips and stuff. Do they tighten up the crank or something?
Nope, the cranks aren't tightened. Most the time, though, if you have sealed bearings in the BB and a relatively firm chain tension, the cranks don't spin around too much.
This video is a bit more like the first in that it's street riding.
If you think the OP was impressive.... watch this.
http://www.youtube.com/watch?v=PjyGiRrWfgY&fmt=18Keep in mind that in most of the shots, this guy doesn't have any brakes on his bike at all.
Pretty crazy stuff. Pretty much all of the stuff in this video was completely unthinkable when I started riding around 7 or 8 years ago.