The spinal discs cushion the pressure on the spinal column. With strong pressure, they exude fluid into the body. In this manner one becomes shorter during the day. In slight pressure, for example in the lying during the night's sleep, they absorb body water, restoring their height; one does becomes somewhat taller after a nights sleep. This fluid release and reabsorbion is important for the metabolism of the spinal, because the supply of nutrients as well as the evacuation of the dross materials takes place based via the body water, because there is no blood supply to the discs.

With the decades, the metabolism of the spinal disks diminishes gradually. The consequence is degenerative disc disease, resulting in reduced mobility of the spine.

Supply and removal of disc fluid depends on changing pressure loads as well.

Hour long, one-sided loads and sitting promote the degeneration of the discs, muscles and ligaments. Also, heavy physical labor, such as in farming, mining, and truck driving frequent require lifting of heavy loads, long-time exposure to vibrations, both which promote the wear on the disc.