A recent paper from the scientific journal Circulation, "Cardiac Effects of Repeated Weightlessness During Extreme Duration Swimming Compared With Spaceflight," has published new findings on the impact of space travel on human hearts. When astronaut Scott Kelly returned to Earth after nearly a year at the International Space Station, his heart had apparently shrunk by more than 25% of its original mass. As The New York Times explained:
A smaller heart did not appear to have any ill effects on Mr. Kelly.
"He did remarkably well over one year," said Dr. Benjamin D. Levine, the senior author of the Circulation paper and a professor of internal medicine at the University of Texas Southwestern Medical Center and Texas Health Presbyterian Dallas.
"His heart adapted to the reduced gravity," Dr. Levine said. "It didn't become dysfunctional, the excess capacity didn't get reduced to a critical level. He remained reasonably fit. His heart shrank and atrophied kind of as you'd expect from going into space."
Without the pull of gravity, the heart does not have to pump as hard, and like any other muscle, it loses some fitness from less strenuous use. For Mr. Kelly, the shrinkage occurred even though he exercised almost every day on the space station, a regimen that has proved effective at limiting the brittling of bone and loss of muscle overall.
Makes sense!
Space travel is known to have some other weird physical effects as well, including bloated heads, brittle bones, and swollen eyeballs.
Note to Future Space Travelers: Prepare for a Shrinking Heart [Kenneth Chang / The New York Times]
Image via Public Domain Pictures
Full Disclosure: I also write for Wirecutter, which is owned by the New York Times Company, which also publishes The New York Times.
