Spines Stretch in Microgravity as Astronauts Return Taller, Then Reclaim Height on Earth

In microgravity, the spine can lengthen by up to about five centimetres, leaving astronauts temporarily taller on return to Earth before gravity compresses the spine within days; the height gain is attributed to loading changes from gravity rather than muscle or bone loss. Historical data from Apollo-Soyuz and Skylab, plus ISS studies, support this, with seated height measurements affecting helmet and suit fit. The article also notes post-flight back injury risk and calls for routine in-flight measurements, post-flight imaging, and exploration of lumbar-focused countermeasures, given implications for future Artemis/Mars-class missions.