BIKES MAY AID SPACE FITNESS.

Byline: Associated Press 

Orthopedist Arthur Kreitenberg has a spacey idea.

The concept hit him while touring a soup-can-shaped room of a space-station replica in 1990 - an exercise bike for astronauts.

``A device like this could allow people to walk rather than crawl on Mars when we get there,'' Kreitenberg said. ``It could help us tame the environment of space, allowing us to explore and colonize.''

The basic idea is two bicycles radiating out from a central pole, similar to spokes on a tire hub.

Kreitenberg and fellow University of California, Irvine, colleague Vincent Caiozzo last week requested a $600,000 grant from NASA to study the cycle.

Keeping astronauts fit in space is one of three big hurdles for human exploration of the far reaches of space, said NASA's Michael C. Greenisen, director of exercise countermeasures at Johnson Space Center in Houston.

``One is radiation. If we can't adequately shield the vehicle such that after a three-year mission the crews don't glow in the dark, we're not going,'' he said. ``No. 2 is figuring out how to keep crews supplied in water.

``The other is that if crew members cannot reach the Martian surface and reasonably expect to get out and stand up and do physical work, we're not going,'' Greenisen said.

In space, without the tug of gravity, muscles don't get any kind of work out and turn to mush.

``It's use it or lose it,'' Caiozzo said.

The only problem with the space bike is that riders must spin around - a lot. Kreitenberg and an astronaut friend went to a merry-go-round and spun each other around and around to figure out how astronauts could avoid dizziness.

``It turns out you only get sick if you move your head around a lot,'' he said.