$17,000 for what?

I heard about this in high school. They do tests like this a lot to see how the body degenerates from lack of use, or how lack of gravitational resistance may effect body (I guess in the sense that if your laying down, you have the least amount of weight on your body?).
Though if I remember correctly, no one in my class said they'd want to lay in bed for three months straight.

I bet the first few days of going to the bathroom are interesting. I wonder how much training they give?

Aside from the isolation from family and home, I can say from experience that any forced bed rest is a nightmare. I did five months of "modified" bed rest while pregnant (generally on my left side). This meant I could get up to go to the bathroom, eat a quick meal, take a brief shower or go the doctor. Generally I was not allowed to be on my feet for more than 15 minutes or so, and preferably not that long for more than once a day. Even at the doctor's office or hospital, they immediately made me lay down. It took a year for my joints to recover.

Just not being able to go out and do anything, visit with family, shop, go to restaurants, parties, movies or whatever was very psychologically difficult. I was well motivated as it meant the survival of my child.