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Jelly belly and chicken legs.

Taking a long journey throug space? Stop, pay toll--the toll weightlessness takes on your body

Q What is it about space flight that's the most fun?

A Floating around weightlessly.

Q Now, what is it about space flight that may prevents humans from spending a lot of time up there?

A You've got it--floating around weightlessly.

You see gravity has shaped the human body, from bines to blood pressure to sense of balance. We're made for gravity--take it away, and we humans are fish out of water.

Astronauts know the feeling. When they go to work, they kiss the pull of gravity good-bye. And their bodies go throug radical changes to adjust. Although astronauts know these changes well, NASA scientists are still puzzling out just how they happen, and whether they get worse the longer you stay in space.

NASA hopes to use data from recent shuttle flights to predict how bodies will endure much lengthier stints in space. After all, NASA's talking about three to six months a pop on space you hold up during such a long spell of weightlessness? What could you incorporate into a space station that would help you out? You might want to keepo the following in mind before you launch your spacestation design (see p. 6).

YOU FEEL LIKE TOSSING YOUR COOKIES

Don't let those thumbs-up photos fool you-even veteran astronauts get queasy in space. They call it space motion sickness, and they don't like to talk about it.

What happens is that your brain gets conflicting signals from your different sense (see p. 23), says Millard Reschke, a NASA biologist who studies the nervous system. The result: total confusion.

Why does this confusion make you sick to your stomach? No one's really sure. One theory is that your brain mistakes its own confusion for the dizziness that can come with poisioning, and makes you throw up to get the "poison" out of your stomach.

Fortunately, space motion sickness usually passes after a couple of days, as your brain learns to rely on one set of signals--coming from the eyes. Still, suppose, during that time, that a nauseous astronaut had to don spacesuit and helmet and venture outside. Barfing into your oxygen line coiuld be hazardous to your health.

Last September, space shuttle astronauts tested a biofeedback device that helps them concentrate on eliminating the symptons of nausea. Can you concoct anything for your space station that would quash the quesies

YOUR BNONES AND MUSCLES WIMP OUT

When cosmonaut Yuri Romaneko returned to Eartjh after spending ten months in Russia's Mir space station, his colleagues wanted to give him the usual Russian greeting--a bear hug. But they held back. They were afraid that Romaneko's bones, after floating so long in space, would crumble in a hearty squeeze.

The problem? Bones are designed to carry weight, and if you're weight-less, your skeleton is out of work. Like many parts of the body, bones weaken if they aren't being used, explains NASA biochemist Joan Vernikos.

For one thin, the skeleton loses calcium, a key component of bone. But that's not all, NASA is now finding that the calcium that stays in your body gets redistributed.

You see, bones, are constantly rebuilding themselves, breaking up old calcium deposits and laying down fresh calcium. On Earth, a lot of that new calcium goes to strengthen key points--like the sides of leg bones--that fight hardest against gravity.

But when you're weightless, says Vernikos, "its no longer necessary to reinforce those key points, and the mineral redistributes itself more evenly. So when you stress a key point, bone will have a greater tendency to fracture."

What's more, muscles atrophy, or shrink dur to lack of use, in space. After all, on Earth, muscles constantly work against gravity--every time you move your arms to take a step. In space, that work disappears, because your limbs weigh nothing.

To counter muscle atrophy, astronauts work out like crazy on board the space shuttle. So do Russia's cosmonauts, some of whom spend months in orbit. Still, the Russians often need weeks of physical therapy to readjust to Earth's gravity. There must be a better way to overcome space wimpiness. Got any suggestions?

YOUR HEAD GETS PUFY AND YOUR LEGS GET SKINNY

"Fat face, chicken legs." That's what astronauts call their appearance in space. It happens becuase gravity no longer pulls blood and other body fluids down toward your legs. Instead, the fluids that normally circulate down there float up into your head and upper body. Astronauts notice stuffy sinuses as a result of this headward fluid shift, but there are far more serious side-effects.

FIrst, your brain gets bamboozled into believing that your body contains too much fluid. The brain relies on nerves in arteries in your neck and chest to keep tabs on your blood pressure. So when fluids migrate to your upper body, those nerves notice the extra pressure the fluids create.

The brain then tries to "dump" this excess fluid by making uou less thirsty and sending you, often, to the space bathroom. After all, urine is just water and waste filtered out of blood.

But remember: When the fluids shifted to your head, the total volume never changed. So what happens when you start dumping fluid? You wind you with less blood--you drop from about five quarts to four.

With less blood to pump around, the heart nedn't work as hard. So it shrinks. But less blood also means, well, fewer blood cells.

Red blood cells carry oxygen around. Fewer of them means that muscles can't work as hard. In weightlessness that's not a problem--muscles don't have to work as hard. But what happens when you come back to Earth a quart short of blood?
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Title Annotation:weightlessness
Author:Pope, Greg
Publication:Science World
Date:Jan 15, 1993
Words:956
Previous Article:NASA's dream house.
Next Article:Don't dis(orient) me!
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