Would you take $18,000 (£11,700) to stay bed-ridden for 70 days straight? And we mean bed-ridden; you must remain horizontal at all times (yes, even when going to the toilet), enduring all the physical pain that involves.
Well, last year, NASA paid about 50 volunteers to do just that, to learn how muscle and bone would deteriorate in such conditions. The research may be useful for lengthy space missions in the future, such as trips to Mars.