Scott Kelly, an American astronaut, recently returned to Earth after nearly a year on board the International Space Station. NASA physicians found that he's now 2 inches taller than his identical twin brother. Kelly was in very low gravity for a year, so there was no gravitational compression bearing down on him.
NBC News describes other effects of spending a long time in space, including a shrunken heart, difficulty with balance, and decreased bone mass:
- Astronauts no longer walk to get in the spacecraft, they float so the bones in the legs, hips and spine experience a significant decrease in load bearing. […]
- Extended spaceflight results in less work for the legs and back: muscles can begin to weaken or atrophy, and this could lead to fall-related injuries and accidents during exploration missions. […]
- The heart doesn't have to work as hard up there: Over time, this could lead to a decrease in the size of the heart.
-via The Mary Sue