Soft tissues around the spine also play a key role in low back pain. There is a large and complex group of muscles that work together to support the spine, help hold the body upright and allow the trunk of the body to move, twist and bend in many directions.

Types of muscles that affect low back pain

Three types of back muscles that help the spine function are extensors, flexors and obliques.

• The extensor muscles are attached to the posterior (back) of the spine enable standing and lifting objects. These muscles include the large paired muscles in the lower back (erector spinae), which help hold up the spine, and gluteal muscles.

• The flexor muscles are attached to the anterior (front) of the spine (which includes the abdominal muscles) enable flexing, bending forward, lifting and arching the lower back.

• The oblique muscles are attached to the sides of the spine and help rotate the spine and maintain proper posture.

Exercise to help low back pain

Back muscles—like any other muscle in the body—require adequate exercise to maintain strength and tone. While muscles like the gluteals (in the thighs) are used any time we walk or climb a step, deep back muscles and abdominal muscles are usually left inactive and unconditioned. Unless muscles are specifically exercised, back muscles and abdominal muscles tend to weaken with age. Physical therapy and exercise regimens to treat low back pain usually focus on strengthening the flexor, extensor and oblique muscles to help reinforce support of the spine and in turn, reducing low back pain and sometimes eliminating the need for surgery.

The role back muscles play in low back pain

When the facet joints or certain other structures in the spine become injured or inflamed, the large back muscles can spasm and cause low back pain and marked limitation in motion.

An episode of low back pain that lasts for more than two weeks can lead to muscle weakness (since using the muscles hurts, the tendency is to avoid using them). This process leads to disuse atrophy (muscle wasting), and subsequent weakening, which in turn causes more pain because the muscles are less able to help hold up the spine.

Chronic stress can also lead to muscle weakness and back pain. Stress causes back muscles to tighten in a fight or flight response, depriving muscles of energy needed to support the spine.

Another key structure in low back pain is the hamstring muscles, the large muscles in the back of the thighs. Patients with tight hamstrings tend to develop low back pain, and those with low back pain tend to develop tight hamstrings. The theory is that tight hamstrings limit motion in the pelvis, so the motion gets transferred to the bottom lumbar motion segments and increases the stress in the low back. Rehabilitation focuses on strengthening the muscles and stretching the hamstring muscles.

Muscles and proper posture contribute to low back pain

Muscle strength and flexibility are essential to maintaining the neutral spine position. Weak abdominal muscles cause hip flexor muscles to tighten causing an increase in the curve of the low back. An unhealthy posture results when the curve is overextended called lordosis or swayback. Proper posture corrects muscle imbalances that can lead to low back pain by evenly distributing weight throughout the spine.

By: Peter F. Ullrich, Jr., MD
September 8, 1999 | Next: Sacral Region
(Updated July 10, 2001 and August 24, 2004)