Astronauts’ Hearts Turn 9.4% Rounder and Spines Stretch Up to 3% in Orbit

1 articles · Updated · spacedaily.com · Jun 21

A 2014 study of 12 astronauts found hearts became about 9.4% more spherical during long periods in microgravity, a visible sign of cardiac deconditioning rather than permanent damage.
Up to 3% height gain in orbit comes from spinal discs expanding and rehydrating without gravity’s constant compression, temporarily lengthening the spine rather than growing bone.
Those spinal changes can bring back pain in flight and a higher risk of herniated discs after landing, while both heart shape and height typically return to normal over weeks or months on Earth.
The findings matter more for longer missions: months in weightlessness could leave Mars-bound crews with weaker hearts and altered spines just before they must function under gravity again.