[alistairSH]

I'm not sure DH mountain bike hits the G-forces that one might encounter in a fighter jet. Maybe some instantaneous instances, but nothing sustained. I'm a mountain biker (nowhere near an elite DHer) and they don't require compression gear to keep from passing out.

Bobsled/luge might be closer, but I have no direct experience.

[dailykoder]

I'd second that. I am far far away from being a pro, but my gut feeling and memory tell me that I felt way bigger forces while doing big, steep dirt jumps than any form of downhill. Though, the pros are actually fast around the corners, unlike me. So maybe there might be some g-forces, but I doubt they are anywhere near an F1 car or something else