Endurance swimming would be as dangerous as a long stay in space. According to a study by Dr. Benjamin Levine, professor of internal medicine at the Southwestern Medical School at the University of Texas and published in the scientific journal Circulation, these two disciplines can lead to a narrowing of the heart.
For his research, the professor compared the effects of 340 days spent in space aboard the International Space Station (ISS) on the body of American astronaut Scott Kelly to the performance of French long-distance swimmer Benoît Lecomte. In June 2018, the athlete swam 2,821 kilometers in 159 days in an attempt to cross the Pacific Ocean, before giving up. Benoît Lecomte is also the first man to swim across the Atlantic.
Result: in both cases, the heart is not solicited by gravity, which leads to atrophy of the organ. “One of the things we’ve learned over many years of study is that the heart is remarkably plastic. It therefore adapts to the load imposed on it ”, explains Dr Benjamin Levine to BBC News.
19 to 27% mass loss
Concretely, how is this phenomenon explained? In space, the body no longer needs to pump blood upwards, because “You are not pumping against gravity”, notes the professor. Swimming for very long periods, an average of 5.8 hours per day in the case of Benoît Lecomte, also modifies the loads imposed on the heart by gravity, because the person is in a horizontal position and not a vertical one. Especially since the swimmer slept about eight hours a night, which means that he spent between 9 and 5 hours each day lying down.
Both hearts therefore began to lose mass. “When we examine the left ventricle [du cœur], we see a total mass loss of around 20 to 25% during the four or five months that Mr. Lecomte swam ”, says Dr. James MacNamara, co-author of the study. “We have seen a mass loss of 19% and 27% for Captain Kelly over the year.”
Fortunately, these cardiac atrophies did not last long term: the hearts of the two men returned to normal size as soon as they returned to dry land, the BBC article said.
–
