I was reading about this a little while ago
your brain basically disconnects the movement controls while you are asleep, so while dreaming you don't actually carry out the actions.

sometimes it gets switched back on while you are still dreaming, and you get sleep walking and stuff, and sometimes it remains disconnected after waking so you can't move.

simplified, but basically the case. not that I'm an expert or anything
( Vipros. clever got me this far, then tricky got me in, Wed 3 Jun 2009, 10:35, 2 replies, latest was 17 years ago)

expert kaoltard
(Bazongaloid, Wed 3 Jun 2009, 10:37, Reply)

works either way
I was saying I'm not an expert, and I'm not a kaoltard
( Vipros. clever got me this far, then tricky got me in, Wed 3 Jun 2009, 10:37, Reply)

Tis bloody scary
It's almost how I'd imagine being buried alive is like. But with more light.
(Potty Jag har smör i min rumpspringa, Wed 3 Jun 2009, 10:39, Reply)

Brains do the funniest things,

(PsychoChomp, Wed 3 Jun 2009, 10:40, Reply)

This is where I envy the brainless masses

(Potty Jag har smör i min rumpspringa, Wed 3 Jun 2009, 10:41, Reply)