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Astronauts and Swimmers Could Have Shrunken Hearts

A strange side effect of both space flight and endurance swimming

In a study conducted by Dr. Benjamin Levine of the University of Texas Southwestern Medical Center in Dallas, an astronaut and an extreme endurance swimmer both exhibited some atrophy of their hearts. Astronaut Scott Kelly and swimmer Benoît Lecomte, despite exercising regularly, displayed the atrophy due to long stretches of time without the load that gravity puts on the human heart.

Kelly spent 340 days at the International Space Station, while Lecomte attempted to swim across the Pacific Ocean, making it 159 days before stopping. He had previously successfully crossed the Atlantic. Though gravity still affected Lecomte, it pulls differently against a horizontal swimmer than against a person upright on land.

Astronauts on the ISS are required to exercise daily in order to counterbalance not only heart atrophy, but also other muscles. In Kelly's case, the exercise was not enough to counterbalance the extended stay in space. For more, head to