The discs between the vertebrae of the spine are soft and act like a cushion for loads through the spine. The disc is sensitive to how much load it carries and for how long. Over time under a constant load, the disc loses water. This loss of water causes the disc to lose height. The disc flattens in an outward direction. These changes are called creep behavior.
Normal discs creep slowly. Studies show that higher loads produce faster rates of creep. Older discs start to degenerate. Damaged or degenerated discs creep faster than healthy discs in young people. There's some research to show the contraction of fibers around the disc, not water loss or fluid flow, is the real cause of creep.
The disc regains its full size and normal shape when the load is removed. Research centered on what makes the discs creep less may help us find ways to prevent disc problems.