centrefugal (I may have spelt that wrong) force. Or magic. Not sure which.

 The G forces pulling you towards your feet is super high if you stand at that angle on the ride. Surely it would be strong enough to where you couldn't stand? I just don't see how its possible, it hurts my back thinking about.

 it actually doesn't need to be much G force, as long as your lined up correctly (eg head pointing to the centre and body in a straight line).

 Well that is if you can stand up long enough. The G forces are rather strong, its enough to be laying on your back and lift you arm up becomes difficult/almost impossible.

 getting up is the hardest bit, but once you're up it shouldn't be to difficult to stay there, although the blood will be forced from your head so you might end up dizzy/light headed if you stayed there too long.