What structural change in the spine leads to frequent back pain for long-duration travelers?

Answer

The discs expand as they decompress because the constant compressive load from gravity is removed.

On Earth, gravity compresses the vertebral column, but in space, this load is removed, allowing the intervertebral discs to decompress and expand, which causes significant muscular and structural strain.

What structural change in the spine leads to frequent back pain for long-duration travelers?
Spacegravitysensationpain