Pablo Alvarezthe Leonese who last April graduated as an astronaut from the European Space Agencyhas attracted attention this Monday with some statements about how life in space affects the human body. ‘On average, an astronaut grows 7 centimeters. Then you return to Earth and return to your normal height,’ he said in an interview on Cadena Ser.
With these words, he who will be the third Spanish astronaut in history, after Pedro Duke and the Hispanic-American Miguel López-Alegríareferred to one of the best-known effects of the conditions in which astronauts live in the International Space Station (ISS) for prolonged periods of time and you are not the only one.
The ‘growth’ that astronauts experience is a consequence that has been studied for decades. In 2018the Japanese astronaut Norishige Kanai announced on his account in the old Twitter that had grown 9 centimeters after spending only 3 weeks on the ISS. ‘I’m a little worried about whether I’ll fit into the ship’s seat Soyuz when I return’, as the seats have a height limit. Later, he rectified and pointed out that he had made an error in the measurement and that I had ‘only’ grown two centimeters in that period of time.
According to studies carried out by NASA and other space agencies, astronauts in space grow an average of between 2 and 5 centimeters. The reason lies in the absence of gravity and how it affects the spine.
The spinal column is made up of vertebrae separated by intervertebral discspads formed by cartilage. These expand due to the absence of the compressing effect of gravity and that is where the growth in height comes from.. Once they return to Earth and the usual conditions of gravity, the change reverts and the astronaut regains his usual height.
That does not mean that the change is harmless and, in fact, it generates discomfort and physical problems. As the intervertebral discs expand, the natural curvature of the spine is flattenedand the absence of gravity also causes the muscles to weaken, which has caused Back pain is a common problem for astronauts who spend long periods in space. A study published in 2016 collected that more than half of American astronauts have suffered back pain during their missions, which 28% rated between moderate and severe. After their return to Earth, they have a risk 4.3 times greater that those who have not gone to space suffer a herniated disc.
For this and other reasons, astronauts continue a strict physical exercise program while maintained in environments such as the ISS. For example, to alleviate the effects of bone loss in space. If an elderly person on Earth loses 1% of bone mass in a year, an astronaut in space loses it in a month. Furthermore, the lack of gravity atrophies the muscles and causes them to lose volume.
Another effect of living in space affects vision and causes two-thirds of astronauts return from space with myopiaalthough when they took off from Earth they had perfect vision.
‘There are two irreversible things: bone mass is not recovered to 100% that you lose and there are permanent effects on the eyes because eye pressure increases and the eyes become deformed‘, Álvarez explained to the media.
Sunita Williams -the NASA astronaut who climbed to the ISS last June with Butch Wilmore on board the Starlinerinitially for an 8-day mission, but they have postponed their return to Earth until February due to the failures of the capsule. Boeing– has also recently spoken about the effects of living in space. ‘The foot calluses They disappear because you don’t walk and nails and hair they grow faster,’ he explained in an interview in September. ‘Without gravity, some face wrinkles They temporarily soften due to the upward displacement of liquid. The backbone It also expands because there is no pressure on the cartilage between the vertebrae, making one slightly taller in space.’ Williams stressed that these changes are reversed upon returning to Earth: ‘you shrink back to your normal height and your back may hurt a little as gravity reasserts itself.’