It's a smart way to spend three months in bed

Benny Elmann-Larsen, Esa project manager

One of the project co-ordinators, Anne Pavy-Le Traon, said the experiment would use electronic imaging to get a better idea of how these problems developed.

"What we want to do is to study these phenomena very closely so that we can devise medication or physical exercises so that astronauts can nip a problem in the bud," she said.

To mimic the environment of space, the volunteers' beds will be inclined, putting their heads below the level of their feet. The participants are allowed to roll over on to their stomachs to eat, but are not allowed to sit up.

Writing theses

If it sounds distinctly uncomfortable, another of the project's scientists, Benny Elmann-Larsen, a project manager at the European Space Agency (Esa), said there were compensations.

"They have a TV in each room, we have a little library here, they can also order books; some of them will be writing theses - things like that," he told the BBC.

"It's a smart way to spend three months in bed. They will have access to computers. The observant listener will say 'how do they use a keyboard?' Well, actually, you can do that while you lie on your belly, the same way as you eat."

Some will have to do leg exercises every day on a flywheel-type device that space scientists believe could help counteract the bone and muscle problems. A daily massage is also available.

Inevitably, however, one or two of the volunteers will drop out before the experiment is up.

"We have carried similar tests over a six-week period and our experience with these indicates we will have quite a few problems," Anne Pavey-Le Traon said.

The bed-rest study is being conducted at the Institute for Space Medicine and Physiology (Medes) in Toulouse. Esa's partners in the research are the French space agency (CNES) and the Japanese space agency (Nasda).