Note to future space travellers: Reduced gravity will shrink your heart

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

In space, your heart gets smaller.
 
In a study published on Monday in the journal Circulation, scientists reported that the largest chamber of the heart of Scott Kelly, who spent nearly a year on the International Space Station in 2015 and 2016, shrank in mass by more than one-quarter by the time he returned to Earth.
 
That just adds to the litany of transformations that the human body undergoes without the steady downward pull of gravity. Astronauts also tend to have swelled heads, squashed eyeballs, shriveled legs and bones that become more brittle.
 
But a smaller heart