Yeah, what RFenst said above, Jade. They just stretch you out...
BTW, you ever watch any of those movies of medieval time where people were put on the rack, and stretched out a bit? Traction is like that, but gentler
You know, even up to Colonial times in the soon-to-be United States, evil-doers would have their arms bound up and attached to draft horses going in different directions, and both their legs done the same way. Then the horses were whipped forward until the limbs came off.
But, I bet that, at the time, their back problems were insignificant...