The Muscles of the Spine
The muscles of the spine include the abdominal muscles that connect and support the front of the spine, as well as the muscles on the back of the spine. The muscles of the spine allow for an acceptable range of motion needed for twisting and bending, as well as muscles that add stability to the spine. The muscles of the spine come in different sizes and lengths. The shorter muscles provide support, and their main function is to expend and contract, enabling us to make fine movements. As the ones attached to the processes expand and contract, the processes are pulled and released like levers, and the body can twist and bend as much as the ligaments will allow them too.
The facet joints are also pulled and released like levers when the short muscles attached to the facet joints expand and contract. But in this case, the plane of each facet joint determines its ability to move in specific directions - sideways, forward and backward. The short muscles at the top of the spine are more horizontally oriented then those of the lower lumbar region. Because of this orientation, they are better suited for rotational movements than are the lumbar facet joints.
Several layers of long muscles located superficial (over) the shorter muscles. The length of the longer muscles and points of attachment to bones and tendons will depend on its function. The medium-length muscles will stretch from one vertebrae to another several inches away. Located outside the medium length muscles are longer groups of muscles that run the entire length of the vertebral column. The erector spinae runs the entire length of the spine. The erector spinae connects as low as the bottom of the sacrum, and as high at the first thoracic vertebrae. When we tighten of contract our muscles on one side of the erector spinae, our spine bends sideways to that side. When we contract our entire erector spinae, our spine arches backwards and we bend backwards, When we relax the muscles of the erector spinae, we resume an upright posture. The erector spinae also braces the spine to keep it from falling forward, much like the cables that keep a flagpole from falling forward. Other muscles of the back include the oblique muscles, flexor muscles, and extensor muscles.
The oblique muscles connect to the sides of the spine and help to maintain proper posture and rotate the spine. The flexor muscles include the abdominal muscles that attach to the front of the spine and aid in arching and lifting the lower back, and in forward bending and flexing. The extensor muscles are attached to the back of the spine, and they enable us to lift objects and to stand erect. This group of muscles includes the erector spinae, which help to hold up the gluteal muscles and the vertebral spine.
The abdominal muscles. The are several layers of abdominal muscles attached to the front of the spine that enables us to bend forward when contracted. These muscle layers include the rectus abdominus, transverse abdominus, and external abdominal obliques.