Studying What Happens When the G Forces Are With Us
This summer, four lucky young males will spend July and August whirling around in Northern California with lodgings, food and entertainment laid on for free.
Or maybe they’re not so lucky. Coffee is banned--no!--because it’s too stimulating. Required clothing is the latest in biosensor vest wear to monitor heart rate and blood pressure. Activities include providing urine samples, doing mental drills, performing regular sitting and standing exercises--and spinning inside a big centrifuge for 22 hours at a time.
Malcolm Cohen, the researcher coordinating these activities, says the goal is not fun, fun, fun but to better understand the effects of gravity on human biology and to test how we adjust to living at higher-than-normal gravitational forces. The studies might, for instance, suggest ways to help astronauts adjust to Earth after stints in space.
In Cohen’s study, four stalwart lads will climb into the 58-foot-long centrifuge at the NASA Ames Research Center in Mountain View and spend a total of 188 hours lounging around, sleeping, eating and watching videos while the centrifuge’s spinning creates forces of up to 2G--twice the Earth’s normal gravitational pull. Endurance will be tested in various ways and compared with endurance at the start of the test.
Many things happen when the body is subjected to extra gravity, says Cohen, a NASA and Stanford University scientist. Fluid, for instance, tends to pool in lower parts of the body, making for thicker legs and (more important) a harder job supplying the brain with blood.
Cohen wants to know if people adjust to this over time, rendering their bodies better able to deal with higher G forces.
Even more would happen if the men were to spin around for weeks and months instead of merely a day at a time. Their sleep would get messed up because, under heightened gravity, the body’s inner clock starts running more slowly, says Charles Fuller, a scientist at UC Davis. (Fuller heads the university’s “chronic acceleration research unit,” where chickens and mice and other critters go on long-term tilt-a-whirl rides.)
And bodies would change shape too. Muscles and bones respond to that extra gravitational yanking by getting thicker and stronger. In a classic experiment in the 1970s, chickens living in a centrifuge for 23 generations at even higher G forces than those planned for Cohen’s subjects emerged beefier, bonier and leaner than poultry at the start of the ride.
Tabloid papers got pretty excited about that fat-loss finding, says Fuller, but it’s a lousy way to get svelte. “When you stop, the body puts the fat back on again,” he says. You’d have to live in a centrifuge indefinitely. Weightlessness also brings about a mess of body changes. We learned about them from Ronald White, associate director of the National Space Biomedical Research Institute in Houston. Many of the changes are similar to what happens if someone has to rest in bed for a long time. (Consequently, a lot of NASA experiments have involved people lying in bed.)
Here’s a sampling of weightlessness changes:
* Without sensing gravity, astronauts find it hard to know what’s up and what’s down--causing space sickness and illusions of suddenly flipping upside down. This passes within days.
* Fluid moves upward in the body, fading wrinkles and narrowing ankles (yay!) but also creating a moon-shaped face and bulging neck veins. (Not so good.)
* This shift in fluid makes the body decide it’s got too much liquid in it. Kidneys start working overtime excreting water. Astronauts stop drinking as much.
* The shift of fluid to the chest and head causes nasal and sinus congestion--and a case of “space sniffles.”
* Sense of taste changes too. “Many space travelers say that foods don’t taste the same,” White says. “They also say they start liking spicy food the best.” Scientist aren’t sure why.
* The chest expands because it’s not weighed down any more by the heart and other organs in the body cavity.
* The heart, arteries and veins get lazy because they don’t have to work so hard getting blood to the upper part of the body. When astronauts come down, they can get dizzy, even faint, should they get up suddenly.
* Longer term, bones get thin and muscle wastes--especially the muscle fibers used to keep the body standing upright against the force of gravity. Body fat increases.... I’ll stay home.
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If you have an idea for a Booster Shots topic, write or e-mail Rosie Mestel at the Los Angeles Times, 202 W. 1st. St., Los Angeles, CA 90012, rosie.mestel@latimes.com.
