The spine is made of bones (vertebrae) and pads of soft tissue (disks). These parts are arranged in three curves: cervical, thoracic, and lumbar. When properly aligned, these curves keep your body balanced. They also support your body when you move. By distributing your weight throughout your spine, the curves make back injuries less likely.

Strong, flexible back muscles help support the three curves of the spine. They do so by holding the vertebrae and disks in proper alignment. Strong, flexible abdominal, hip, and leg muscles also reduce strain on the back.

The lumbar curve is the hardest-working part of the spine. It carries more weight and moves the most. Aligning this curve helps prevent damage to vertebrae, disks, and other parts of the spine.

Disks are the soft pads of tissue between the vertebrae. The disks absorb shock caused by movement. Each disk has a spongy center (nucleus) and a tougher outer ring (annulus). Movement within the nucleus allows the vertebrae to rock back and forth on the disks. This provides the flexibility needed to bend and move.