A study of being bedridden could help astronauts

The Ashmont sisters spent a month in bed as part of a study on the physical effects of being confined to bed rest.

SAN DIEGO, California (CNN) -- Meet the Ashmont twins -- 24-year-old Stacey and Casey.

They left behind their modeling careers and cleaning business in Atlanta, Georgia, to come to the University of California, San Diego, and spend a month in bed.

Why? To help scientists understand what happens to people physically if they're confined to bed rest. It's information that will also help astronauts in space, since lack of gravity is almost the physical equivalent.

By a flip of a coin, Casey got assigned the bed by the window and no exercise. Stacey, on the other hand, has to exercise 45 minutes a day, six days a week.

On Day 29, boredom had yet to set in. "We have a TV, we have our books, we have our journals that we're keeping," said Casey.

It doesn't hurt that they're each making $100 a day. Another twin in the study likened it to a paid vacation.

Just down the hall, the Smith twins from Orlando -- Ray and Ron -- saw the study as an opportunity to study for a career change and work on their game of gin rummy.

Visits from astronaut Bill Shepherd also help the time pass. "We're moving toward a period where we understand how to have people living and working and being healthy in space indefinitely. There are big questions about how to do that," Shepherd says.

To help get those answers, the twins have to do everything in bed. That means no bathroom breaks.

Alan Hardens, of the University of California, sympathizes with the study participants. "They have to take a head down tilt shower, so it's very difficult and a very challenging protocol for our subjects," he says.

As a matter of fact, their heads are always tilted down at a 6 degree angle, mimicking the effects of being in space.

"In other words, you get a fluid shift up towards your health, you have a lot of muscle atrophy, you lose blood volume, you start to lose bone," says Hargens.

Why put both twins through the trauma? "The beauty of doing twins is we can essentially study the same person at the same time under two different conditions," says Stuart Lee of the Johnson Space Center.

They're also finding out if exercising at a vertical angle can help prevent that physical deterioration whether you're in bed recovering from an injury or confined to outer space.

So how did Day 30 feel when it was time to get up?

"If you can make it here, you can make it anywhere," the twins say.