Researchers have found that a longer stay in space can shrink a person’s heart. They said even physical exercise could not restore the size of the heart.
The researchers analysed data from retired astronaut Scott Kelly’s almost one-year-long stay on the International Space Station (ISS) in 2015-2016. This data was compared with that from an elite swimmer, Benoît Lecomte’s swim across the Pacific Ocean in 2018. The findings have been published in a journal, Circulation.
The study revealed that both the men lost mass in their heart’s left ventricle over time, the Daily Mail reported. It found that in the case of Kelly, the long-term weightlessness changed the shape of the heart, shrank it and even exercising was “not enough to counteract the effects of prolonged weightlessness on the heart”.
The shrinking of heart in size happened due to differential nature of gravity on the earth and in the space. Gravity on the earth keeps the human heart pumping blood and maintaining the size it has.
However, due to the microgravity in space, the heart does not require to work as hard to pump blood around the body. This change in the mechanical need of heart causes atrophy – a reduction in tissue, the report explained.
“The heart is remarkably plastic and especially responsive to gravity or its absence,” leader of the study Professor Benjamin D Levine at University of Texas Southwestern Medical Centre was quoted as saying.
“Both the impact of gravity as well as the adaptive response to exercise play a role, and we were surprised that even extremely long periods of low-intensity exercise did not keep the heart muscle from shrinking,” he said.
This phenomenon raises a serious concern among future astronauts if they plan to go on a long-term space flight.
WHY DOES SPACE AFFECT HEART?
Compared to the earth, the force of gravity is weaker in the space, where astronauts have gone till now. This means that the muscles barely have to work. During their stay in space, the astronauts have an exercise regimen to stop them from losing large amounts of muscle mass.
Further, back on the earth, heart keeps blood in circulation generating pressure to counter the planet’s gravity. This mechanism also helps heart maintain its size and function properly.
Therefore, when this gravitational force vanishes in space, it reduces heart’s performance. Heart steadily shrinks as a result.
Moreover, a long-term stay in space decreases bone density, increases the risk of bone fractures and also degrades muscles.
WHAT THE STUDY HAS FOUND?
Researchers found both Kelly and Lecomte lost mass from their left ventricles over time – Kelly 0.74 grams a week and Lecomte 0.72 grams a week.
Both men suffered an initial drop in the diastolic diameter of their hearts’ left ventricle. Kelly’s heart size dropped from 2 to 1.8 inches (5.3 to 4.6 cm), while Lecomte’s reduced from 1.9 to 1.8 inches (5 to 4.7 cm).
However, the report said, “The left ventricle ejection fraction (LVEF) – the amount of blood pumped out of the left ventricle, measured as a percentage – as well as markers of diastolic function did not consistently change in either individual throughout their campaign.”
Meanwhile, researchers emphasised that further study was required to understand the results and how they can be applied to the general population, “as opposed to extraordinary feats by two unique individuals”.
WHAT EXERCISES ASTRONAUTS THEY DO IN SPACE?
Cycle Ergometer: Astronauts pedal on a bicycle-like machine. It is also used to measure fitness – check heart rate and how much work is being done.
Treadmill: Walking or jogging on the treadmill is like walking on the earth.
This Article firstly Publish on www.indiatoday.in