The paraspinal muscles are the muscles that run next to, and roughly parallel with, the spine. They consist of many small muscles that are attached to the vertebrae and control the motion of the individual bones, as well as assist with the larger motions of the whole trunk, or core, area. Together with other muscles, they help support the spine and keep it in proper alignment. They also limit the range of motion of the spine, which helps to prevent injuries to the disks and spinal cord caused by overextension.

In human anatomy, nearly all skeletal muscles work in pairs. While one muscle is contracting, or getting shorter, another muscle must get longer to allow movement. When you bend forward, your paraspinal muscles are lengthening; when you stand up again, they are contracting to pull you back to a standing position. Paraspinal muscles on the left and right side of your body work together in the same way when you are bending sideways. When you are not bending, the paraspinal muscles keep your spinal column in vertical alignment while you are sitting or standing.

Paraspinal muscles are thought to play an important role in preventing serious back injuries, such as a herniated disk. When you experience a back spasm, it is often a paraspinal muscle tightening up, which is a warning signal that your back is either bearing more weight than it should, or bending and twisting improperly. Paraspinal muscle spasms are extremely painful; the pain normally stops a person from doing whatever activity caused the pain, before a more serious injury to the disks or spinal cord can occur. In this way, a back spasm can prevent a serious injury, as well as protect an existing injury while it is healing. A paraspinal muscle strain, while very painful, will heal much more quickly than a disk injury.

The paraspinal muscles do not work alone; they are part of an interconnected network of muscles that wrap around the chest, abdomen, and pelvis. All of these muscles work together to protect the spine and allow movement within a safe range. Weak abdominal muscles make the muscles of the back work harder to compensate for the weakness, which can lead to a strain in one or more of the paraspinal muscles. Excess body weight, especially weight carried on the front of the body, can also contribute to an overload of the back muscles. Low back pain is one of the most common complaints of pregnancy, as well as in people who are overweight or obese.