Muscles are often categorized according to their function using the terms “flexor” or “extensor.” The muscles and ligaments in the spine work to hold the spine upright, and to allow forward bending (flexion) and backward bending (extension), as well as rotation from side to side and combinations of those activities.

There are many muscles that contribute to motion and stability in the cervical spine. The trapezius muscle is a flat, triangular muscle covering the upper and back part of the neck and shoulders. Other muscles that lie deeper in the neck are called the scalene muscles. They flex and rotate the cervical spine.

The muscles of the lumbar region of the back act in various combinations to allow flexion, extension, lateral flexion and rotation. Flexion and rotation can also occur together, in a coupled motion.