Spaceflight osteopenia

Spaceflight osteopenia means that astronaut's bones get weaker during spaceflight. This happens because when astronauts are in space for a long time, gravity isn't pulling on their bones like it does when they're on Earth, so the bones don't get enough exercise. Over time, this can make them weaker, like when you don't use some of your muscles for a few weeks, they can get weaker too. Astronauts do special exercises and take medicine to help their bones stay healthy while they’re in space.