A long space voyage is similar to an endurance swim: in both cases, it can lead to atrophy of the heart muscle. Scientists at the University of Texas at Dallas, led by Professor Benjamin Levine, came to this conclusion after comparing the effects on the heart of astronaut Scott Kelly, who spent an entire year in space, and swimmer Benoît Lecomte, who specializes in marathon distances. In both cases, the reduced load on the heart compared to normal gravity led to its atrophy. In both cases, there was not enough physical activity to prevent such changes. This study may prove to be extremely important for organizing future long-duration spaceflights, such as the expeditions to Mars that NASA plans to undertake in the coming decades.
In the absence of gravity, the load on Captain Kelly’s heart decreased and it began to lose mass. Scott Kelly spent 340 days aboard the ISS, allowing specialists to study the effects of prolonged weightlessness on the human body. On June 5, 2018, Benoa Lecomte attempted to swim across the Pacific Ocean (he had previously swum across the Atlantic Ocean). In 159 days, he covered 2821 kilometers and then stopped swimming. Since he spent a lot of time in the water in a horizontal position, this also changed the load that gravity placed on his heart. Lekomt swam an average of 5.8 hours per day and slept about 8 hours, which means he spent 9 to 17 hours per day in a horizontal position. Scientists sometimes simulate spaceflight conditions by placing volunteers in beds, because lying down keeps the heart and head at the same level, reducing stress on the heart. However, according to Dr. Levin, prolonged immersion in water simulates orbital conditions even better.
Swimming long distances is like flying into space. We explain quickly, simply, and understandably what happened, why it matters, and what will happen next. The number of episodes should remain the same. End of story.
Podcast Advertising Since neither the astronaut nor the athlete had to pump blood to their heads to overcome gravity, their hearts began to atrophy. “When we looked at the left ventricle, we found a mass loss of 20-25% during the 4 or 5 months that Lekomt was in space,” explains co-author and University colleague James McNamara. “And for Captain Kelly, the loss of heart mass during his year in space was between 19% and 27%.” Exercise can help prevent some of this weight loss. Astronauts on the ISS are already actively exercising to prevent the loss of muscle and bone mass that inevitably occurs during long stays in orbit. But even an intensified training program could not help Captain Kelly avoid partial heart failure. In the case of Lekomt, researchers initially believed that the physical exertion experienced by the swimmer in the water was sufficient to prevent any loss of heart tissue mass. “I was absolutely sure that Ben’s heart wasn’t going to atrophy, but the beauty of science is that you learn the most when the unexpected happens,” Dr. Levin admitted. “And it turns out that when you swim that many hours a day, you don’t work as hard as Michael Phelps.” Throughout the swim, Lekomt moved his legs very slowly. “His physical activity was not as high as Levin thought, but a low level of activity does not protect the heart from adapting to the absence of gravity.” However, this adaptation does not last long, and the astronaut’s and athlete’s hearts quickly returned to normal when they hit the ground. However, the chambers of the heart, called the atria, expand due to changes in fluid flow in the space. This can lead to a condition called atrial fibrillation, in which the heart beats faster and irregularly. This can not only interfere with exercise but can also lead to a stroke. During spaceflight, the development of cardiovascular disease may be accelerated due to increased exposure to radiation. Astronauts are screened for signs of atherosclerosis, but they usually go into space at an advanced age, and the problem worsens over time. All of this is very important because the consequences of a heart attack in space can be catastrophic. Currently, Professor Levin is working as part of NASA’s “Code” program, which involves sending 10 astronauts on a long-term mission into space. Researchers plan to use the latest scanning equipment to subject members of the future crew to a variety of tests in order to get an accurate picture of how the heart works in the conditions of space travel.