Do you grow 2 inches when you go to space?

Once humans reach their adult height, there’s very little anyone can do to make them taller. There is incredibly painful bone lengthening surgery—but it's rather extreme. Unlike planet-bound Earthlings, however, astronauts can gain several inches during long stays in space. But recent research shows there's a catch: As soon as they return to Earth they not only lose that height boost, but the whole process can lead to back problems, reports Hanna Devlin for The Guardian.

Researchers examined six NASA astronauts, each of whom spent between four and seven months on the International Space Station. Before liftoff, each astronaut had an MRI scan of their spine. Upon their return they were scanned two more times, once immediately following their arrival on Earth and again two months later, according to a press release.

The scans showed that while in space, the lean muscle mass supporting their spines atrophied, decreasing by an average of 19 percent. During follow-up scans, the astronauts had only recovered about two-thirds of their preflight muscle mass. The decrease put the astronauts at four times the risk for spinal disc herniation compared to control subjects. The astronauts also “grew” an average of about two inches because of "spinal unloading." But that height soon disappeared as they readjusted to the weight of their bodies back on Earth. The research appears in the journal Spine.

About 70 percent of astronauts report spine discomfort after only a few days in space, writes Devlin, and half experience back pain on their return to Earth. It was thought that the pain was caused by the swelling of spinal discs when the weight of the body was lifted, but the MRI scans show no evidence of such swelling. Lead author of the study Douglas Chang of the University of California, San Diego, says they will need to conduct more research to figure out exactly what is going on. 

Lewis Dartnell, an astrobiologist at the University of Westminster tells Devlin that this new research highlights one of the weak links in plans to visit Mars: the human body. Having slipped discs or extreme back pain when arriving at the Red Planet after two years in space could prove deadly.

“The Moon is like a long weekend’s holiday. You’re fine to take photos of your footprints and plant some flags,” he said. “When you get to Mars there’s a serious chance you might fall off the ladder when you climb out of the spacecraft. It might be much more serious than a bit of a gripe and a joke. If you break your hip on Mars, you’re basically dead.”

In the press release, Chang says astronauts may be able to counter some of the changes through core-strengthening exercises and workout regimens suggested for people with back pain on Earth. Yoga could also be useful to help reduce problems. But more tests are needed to figure out which exercises (or if any at all) could help protect astronaut spines—or if entirely different protective measures are needed.

Space travel: The final frontier  |  Photo Credit: iStock Images

Key Highlights

• Astronauts get a bit taller in space because of the decompression of the disks of the spinal column.

• The disks are slightly compressed when one is living on Earth, thanks to the effects of gravity.

• In space, the disc expands and the spine lengthens, as there is near-zero gravity, and the astronaut is taller.

The spine's elongation in microgravity can add two inches to a six-foot-tall astronaut. The increase is credited to the lack of compressive forces of gravity.

Astronauts in space can grow up to 3 per cent taller during the time spent living in microgravity, NASA scientists say. Therefore, if an astronaut is a 6-foot-tall (1.8 meters) person, he or she could gain as many as 2 inches (5 centimetres) while in orbit, says the Scientific American.

But this increase in the height of astronauts over the first 3 to 4 days of weightlessness in space is not permanent when they return to Earth. On terra firma, gravity pulls on them once again and astronauts will typically return to their pre-flight (normal) height after a few months. 

After living for nearly a year aboard the International Space Station, NASA astronaut Scott Kelly is two inches taller than his identical twin brother Mark, reports CNBC.com.

Not just in space, gravity affects our height in day and night:
Did you know our height changes throughout the day? In fact, our height changes from morning to night. Though it has nothing to do with the circadian rhythm, as the day goes on and as we are up and about - gravity compresses our bodies. When we lie down at night, gravity no longer pulls in a direction to make us shorter so our bodies stretch and we return to our taller height again, reports Stem.org. 

What else changes in the body during space stay?
While in space, the decompression of the discs of the spinal column are not the only changes happening to an astronaut's body. Since they do not walk to get in the spacecraft, they float so the bones in the legs, hips and spine experience a significant decrease in load-bearing. That affects the bone breakdown and a release of calcium, leaving the bone more brittle and weak. Astronauts are also more susceptible to the risk of kidney stone formation and bone fractures. Since they do not get to work their legs and back: muscles, they also develop muscle weakness. Blood circulation issues arise during a stay in space and blood is flowing more in the upper part of the body and a little less in the lower extremities, astronauts often have a puffy face and legs that are smaller in circumference. Stay in space also affects heart size, creates balance issues with the ear's fluid, and can cause disorientation. High levels of exposure to radiation in space can also have cancer-causing effects. Also, with no day o night as on Earth, the circadian rhythm can go for a toss, leaving many organs and organ systems confused.

Upon return to Earth, astronauts are given space and facilities to slowly return to things that we take for granted - such as walking, hugging, balancing as they walk or run, turning etc.

Will Richard Branson and Jeff Bezos find themselves taller after their respective space flights? No. Unlikely. Amazon-founder billionaire Bezos' New Shepard spacecraft will go on a short suborbital flight. Though it will take the crew past the Kármán Line, the internationally-recognized boundary of space, at nearly 330,000 feet, or roughly 62 miles above the Earth, the module will return to Earth in 11 minutes. Virgin Galactic's Richard Branson, whose flight earlier this month aboard Galactic Unity 22 hit a peak altitude of around 282,000 feet, surpassed NASA's designated Earth-Space boundary of 50 miles, but fell well short of the Kármán Line. BUT neither Bezos, nor Branson's teams will be on an orbital flight - a height that the ISS is at and are too short a duration for the spine to achieve the decompression that astronauts onboard the ISS witness.

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