The Long and Short of How Back Muscles Work
Low back pain is very common in the United States and causes disabling problems for many adults. Despite today's technology and new ways to look inside the body, it's still a mystery why the back "goes out." Until we know what causes muscle injury, it is difficult to prevent or treat it.

There is a new push in medicine for doctors, physical therapists, and other scientists to find out what causes back pain. So far, it looks like the muscles of the back hold the key. When the muscles don't function properly, the spine is at risk for injury.

Studying the muscles of the back or spine, it seems that there are two major groups. One group is the deep and short muscles that go between two or three bones of the spine. The second group is the long muscles that cross many vertebrae. By working together, the short and long muscles protect the discs, ligaments, and joints of the spine from injury.

Other muscles are also important in holding the back stable, especially with so much daily bending and strain. The abdominal muscles give support and pressure much like a corset or girdle. This tension keeps the bones of the spine from sliding sideways or turning when they shouldn't. Even the diaphragm, the muscle that goes up and down with breathing, appears to add pressure to support the back. All of these muscles work together to safely hold the spine steady during daily activities.

The muscles of the back and abdomen also act as tension springs to hold the spine stable. For example, when the spine is stressed too much, muscles on either side of the spine contract together at the same time. This is called cocontraction. This keeps the back in balance when carrying heavy items, repeating the same movement over and over, or making a sudden movement.

Muscle training has been shown to have a positive effect on the back. How this works is still largely a mystery. This type of training appears to increase muscle strength and endurance, improve muscle coordination, and improve posture. All of these together may help prevent back injuries. Scientists will continue to study each muscle group in the backs of healthy adults. By comparing this information with similar studies of injured back muscles, better treatment for back pain is possible.
Gerold R. Ebenbichler, et al. Sensory-Motor Control of the Lower Back: Implications for Rehabilitation. In Medicine & Science in Sports & Exercise. November 2001. Vol. 33. No. 11. Pp. 1889-1898.