if we're ever going to send people to Mars and expect them to be able to stand up when they get there, their spacecraft is going to need exercise facilities. However, a fully equipped gymnasium won't be necessary, according to the experts; a few high-tech versions of those workout gadgets peddled by washed-up movie stars and sports personalities on late-night TV should do the trick.

But experience suggests that exercise alone might not be enough to counter the negative effects of space travel.

Motion sickness is the most common complaint, but more than half the astronauts also reported headaches, respiratory problems, and a condition called 'facial fullness' in which blood pools uncomfortably in the face.