The European Space Agency says volunteer "pillownauts" completed a test of 21 days in bed with their feet up, all in the interest of spaceflight and science.

When astronauts return from a long flight they can need days to recuperate from the effects of living in weightlessness. Bed rest studies such as the one just completed in Toulouse, France, can help scientists find the best way to help returning astronauts' bodies return to normal, scientists said.

While resting in bed and getting paid for it might sound easy, participants dealt with days of monotony, constant tests and a strict diet without being allowed to get up for a walk, fresh air, a shower or even the toilet, an ESA release said Tuesday.

"The first days of each session were the worst," study volunteer Marc Marenco said. "The body needs to adapt and I had migraines and backaches."

Just like real astronauts, the pillownauts needed time to readjust to upright life in Earth's gravity before they could return to normal life.

They said they were proud of their contribution to the science of human space exploration as well as helping bedridden people on Earth.

"We are a reference for many articles, I think the data will help scientists move a step further in their research," Daniel Fandino, who works in a bar when not volunteering to lie down for 3 weeks, said.