NASA found astronauts can become up to 3% taller in space; their spines lengthen without Earth’s gravity, then compress again after landing

Astronauts aboard the International Space Station actually grow taller due to the absence of gravity. This temporary height increase occurs as spinal discs decompress and elongate in microgravity. Upon returning to Earth, gravity compresses the spine, reversing the height gain. However, astronauts experience muscle atrophy in their lower backs which takes time to recover. This can lead to an increased risk of herniated discs after long-duration spaceflight.