Spending a very long time in space has something in common with extreme endurance swimming. Both can cause the heart to contract.
This is the conclusion of a study comparing the one-year effect of astronaut Scott Kelly in space with the marathon swimming by athlete Benoit Lecomte.
Both remove the load on the heart that is normally applied by gravity and cause the organs to atrophy.
In both cases, exercise alone was not enough to combat changes in the heart.
The study was led by Dr. Benjamin Levine, a professor of internal medicine at the University of Texas Southwestern Medical Center in Dallas, and is published in the journal Circulation.
This study will affect very long journeys in space, such as NASA’s expedition to Mars, which it plans to mount in the coming decades.
“One of the things I’ve learned over the years is that the heart is very plastic, so it adapts to the load it puts on,” said Professor Levine, who is also the director of the Institute for Exercise Environment. I am. Medicine, a collaboration between UT Southwestern and Texas Health Press Vitalian Hospital Dallas, told BBC News.
“In space flight, you don’t have to pump blood against gravity, so you don’t have to pump blood uphill.”
Scott Kelly stayed at the International Space Station (ISS) for 340 days, allowing scientists to study the effects of long flights on the human body.
On June 5, 2018, Benoit Lecomte embarked on an effort to swim in the Pacific Ocean, which had previously crossed the Atlantic Ocean.
He swam 2,821km in 159 days and eventually abandoned the attempt.
After swimming for a very long time, gravity also changes the load on the heart because the person is in a horizontal position rather than vertical.
Lecomte swam an average of 5.8 hours a day and slept for about 8 hours each night. This meant he was spending 9 to 17 hours each day in a prone state.
Scientists sometimes use rest studies to simulate space flight because there is no head-to-foot gradient that stresses the heart when lying down. However, Professor Levine said long-term flooding in the horizontal position is a better model of the time spent in orbit.
“This time, we’ll remove the head-to-foot gradient and then put the person in the water, so we’ll adjust that gradient as well. It’s like being in space,” says Professor Levine.
As Professor Levine says, both men are no longer pumping blood uphill, so their hearts have begun to lose mass.
“Looking at the left ventricle [of the heart] During the four to five months that Lecomte was swimming, we can see that the total mass is reduced by about 20-25%, “said Dr. James McNamara, also co-author of the UT Southwestern Medical Center. ..
“In particular, 19% and 27% of Captain Kelly’s mass was lost in a year.”
Motion, however, counteracts the process of mass loss. Astronauts on the International Space Station (ISS) are already undergoing intense retirement homes to reduce muscle and bone waste that also occurs in orbit.
Still, this retirement home wasn’t enough to prevent the heart atrophy seen in Captain Kelly.
At the beginning of the study, researchers wondered if the amount of physical exercise Lecomte was doing in the water was enough to prevent the exhaustion of heart tissue.
“I absolutely thought Ben’s heart wouldn’t atrophy. That’s one of the good things about science. You learn the most when you find something unexpected,” said Professor Levine.
“If you swim for hours a day, you’ll find that, unlike Michael Phelps, he doesn’t swim as hard as he can.”
Instead, Mr. Lecomte kicked his foot relatively lightly throughout. “It’s not that much activity. Low levels of physical activity don’t protect the heart from adapting to the lack of gravity,” said Professor Levine.
However, the adaptation of the heart is not long-term-the hearts of both men returned to normal when they returned to Terra Farm.
However, the chamber of the heart, known as the atrium, expands in space, partly due to changes in the way fluids pass. This can lead to a condition called atrial fibrillation, in which the heart beats fast and irregularly. It can impair exercise, but it can also increase your risk of stroke.
There is another risk to this important organ from space travel. Higher radiation levels in space can accelerate coronary heart disease. Astronauts are screened for atherosclerosis, but astronauts are generally middle-aged, and scientists know that this is a problem that arises with age.
This is important because having a heart attack in space can be catastrophic.
Professor Levine is part of a NASA program called Cipher, which will send an additional 10 astronauts into space for long-term missions. Researchers apply a variety of tests and high-tech scanning methods to the crew’s heart to obtain more detailed images of heart function in space.
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