MADRID
For some years now, space agencies in the United States and Europe, NASA and ESA, respectively, have set their sights on two ambitious goals: to return to the moon and establish a launcher or orbital station, and to travel to Mars. , two challenges that will force humans (astronauts or tourists) to spend long seasons in space.
Therefore, knowing the effects of weightlessness on the body is of critical importance. And it is that, on Earth, the heart’s effort to maintain blood flow and pump blood throughout the body and counteract gravity, helps it maintain its size and functioning, but in space, where there is no gravity, the heart shrinks.
During one of these studies, NASA held astronaut Scott Kelly for an entire year on the International Space Station (ISS).
Now, a new study published in Circulation (the journal of the American Cardiology Association) has compared Kelly’s endurance test to the feat of Benoît Lecomte, an elite swimmer who in 2018 crossed the Pacific Ocean swimming for investigate the impact of long-term weightlessness on the heart.
Immersion in water is an excellent model of weightlessness, as water compensates for the effects of gravity, especially in a prone swimmer, a specific swimming technique used by long-distance endurance swimmers.
During her stay at the ISS, Kelly exercised six days a week, one to two hours a day, during her 340 days in space, from March 27, 2015 to March 1, 2015. of 2016, and used a stationary bike, a treadmill, and did resistance exercises.
Lecomte, meanwhile, swam for 159 days – from June 5 to November 11, 2018 – and covered 1,753 miles, averaging nearly six hours a day, but the effort didn’t stop him from his heart shrank and weakened.
The comparative analysis revealed that in their tests both Kelly and Lecomte lost too much of their left ventricles (Kelly 0.74 grams / week; Lecomte 0.72) and both suffered an initial decrease in diastolic diameter. left ventricle of his heart (Kelly’s decreased from 5.3-4.6 cm, Lecomte’s decreased from 5 to 4.7 cm).
Not even the most sustained periods of low-intensity exercise were sufficient to counteract the effects of prolonged weightlessness.
This study, however, recalls that these are two extraordinary feats and that to understand how the body responds to extreme circumstances will require more studies that can be extrapolated to the general population (potential space tourists).
In any case, the study corroborated that the heart is remarkably plastic and responds especially to gravity or its absence but it was a surprise to see that “even extremely long periods of low-intensity exercise do not prevent the heart muscle shrinks, ”explains Benjamin D. Levine, lead author of the study and professor of internal medicine at the University of Texas.