Long-term exposure to weightlessness induces physiological changes that strongly affect astronauts’ health and performance. At the end of February 2005, 24 women, all carefully selected volunteers, will remain in bed for two months. They are not allowed to sit up for anything ““ even eating and showering. Not being an astronaut, this is the closest one can get to experiencing the effects of long-term space missions on the body. The aim of the study is to improve countermeasures that help prevent the loss of bone mass, muscular atrophy and changes in the cardiovascular system.