Astronauts can become temporarily taller because microgravity reduces the loading that normally compresses the spine. Changes in spinal curvature and spacing increase body height without making the leg bones grow.
The spine is not a rigid pole
On Earth, the spine supports the body against gravity. In orbit, astronauts and their spacecraft are in continuous free fall. The spine is unloaded and can lengthen, so measurements taken in space can differ from measurements taken before launch.
Why this matters for spacecraft
A seat or spacesuit must accommodate the person who will actually use it in flight. NASA studies changes in seated height and the spine to help design equipment that fits across a mission.
Is the increase permanent?
The height change is generally temporary as normal loading resumes after return. It is separate from spaceflight-related bone loss. Becoming taller in orbit does not mean bones are becoming stronger; NASA studies both spinal changes and skeletal health.
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Sources and evidence
- NASA — Spines under scrutiny ↗
Scientific background for the explanation above.
- NASA — Bone changes ↗
Scientific background for the explanation above.
Sources consulted: 16 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial publication with institutional sources and a direct answer.