'masquerading' is a bit of a misnomer. Lying in bed simulates some of the effects that zero gravity has on the body. This article has a decent introduction:
NASA needs more volunteers for its bed-rest study, which helps doctors understand what a lack of gravity does to the body.
In the lunar study, you lie down for 21 days, with your body tilted so your feet support one-sixth of your weight, which mimics gravity on the moon. The longer-term study simulates the lack of gravity you would experience in a space station sojourn or while traveling to Mars. In that study, Archuletta lay in bed for 50 days, with her head declined, six degrees below the rest of her body.
A hospital ward is a good place to run these tests, because they're already rigged with monitoring equipment. If you run experiments on multiple subjects, it makes sense to stick them in the same ward.
Effects of lying down:
Lying on your back for long periods simulates what happens to your muscles and bones in space. When you have no gravity pulling you down, your muscles don't have to work hard to move you across the room, and your bones don't have much weight to support, so they weaken.
The results of these studies can be found on NTRS.
crash labs where cadavers drop to earth in simulated splash-downs
That sounds like a crash test for a landing capsule, in this case Orion.