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Wednesday, February 28, 2024

Column: Health in space!

It’s easy to take for granted how well our bodies work, at least most of the time. Bones stay strong and rigid for support, food flows through the digestive tract, and we constantly breathe in and out without conscious thought. Obviously, any one of these things and more can go wrong if you’re unlucky, but for the most part, the body stays together in an impressive balance.

Of course, humans evolved these traits over hundreds of thousands of years of life on Earth. What happens when we’re miles away from Earth itself, either in orbit around the planet or traveling elsewhere?

It’s hard to guess and even harder to study. After all, there aren’t any microgravity places on Earth that we can put people to study them. All we have are the past and current astronauts, both on short-term shuttle missions and long-term stays on the International Space Station (ISS).

Tracy Caldwell Dyson, a NASA astronaut and UC Davis alumna, has experienced both. Dyson spent 12 days on a shuttle to travel to and work on adding instruments to the ISS in 2007. On April 2, 2010, she launched from Kazakhstan to the ISS and lived on board for 176 days. In that time, she also performed three space walks to complete a crucial emergency repair.

With so much stress and so little gravity, how did her health fare?

“I don’t have anything from the spaceflight that I wasn’t able to recover from,” Dyson said.

Wait, what? How about bone loss or muscle atrophy? Of the spaceflights that have happened, bone and muscle loss is one of the most common side effects.

“That was the one very surprising thing, I didn’t experience any bone loss,” Dyson said. “I didn’t even have to supplement that with any medication or anything like that.”

Dyson was lucky. When people are in space, the body experiences a number of extreme changes. Like I mentioned above, bone and muscle density loss is one side effect of being in space. Even when you spend most of your time sitting at a desk in class, your bones and muscles still need to be able to support the weight of your body against gravity so that you can sit or stand up straight. Without gravity to give resistance, bones and muscles may atrophy. Use it or lose it.

One side effect that Dyson did experience, as seen in pictures and videos of her stay on the ISS, is fullness of the face. This is because of the redistribution of fluids around the body.

Right now, you are full of water. However, you probably don’t feel it most of the time since you’ve become used to it over your entire life. Gravity tends to pull that water down toward the lower body; when gravity isn’t in the picture, the fluid redistributes so that it is about equally spread through the body. This causes fullness in the face of astronauts as fluid migrates toward the head.

The different fluid flow can also be dizzying. When a person closes their eyes, they are still able to tell how their head is oriented in space. This is because fluid flow in the inner ear sends signals to the brain on which way is up (think of how when you tip a glass of water, the water moves relative to the glass). When you’re in space, the fluid in the inner ear doesn’t flow and so it’s difficult to tell which way is up or down. To a certain extent, it doesn’t really matter which way is down; one of the pictures Dyson showed at her lecture was of half of the astronauts on the “floor” of the ISS and the other half on the “ceiling.”

Becoming uncertain of how you’re oriented, however, can present serious problems when you need to know where you are; for instance, on a space walk. NASA tries to solve this by training astronauts in the Neutral Buoyancy Lab (basically a huge indoor swimming pool with an ISS model on the bottom), where astronauts put on their full suits and practice how to maneuver while floating.

This isn’t a perfect model, since any dropped tools or equipment will simply sink to the bottom rather than float away, but the pool combined with virtual reality helps prepare astronauts for the other worldly experience of walking in space.

How to prepare for the other problems of living in space, such as anemia, low plasma levels and mental health of the astronauts? It’s hard to say without more people to test.

The only way to know for sure is for manned spaceflight to continue, slowly but surely, into the future.

AMY STEWART can be reached at science@theaggie.org.


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