Imagine 100 billion dollars. This is the annual cost of back care in the United States. The high rate of repeat back pain and chronic disability accounts for much of this price tag.

There's a new theory about why low back pain (LBP) occurs over and over in some people. It's called the motor control theory. The theory says that patients with chronic LBP don't use the trunk muscles with the same timing and force as patients without back pain. For example the muscles are slow to respond when there's sudden trunk loading or increased trunk movement. Studies also show injuries to the spine can lower the set point so that pain receptors turn on sooner.

In this study, trunk flexion and extension were compared in two groups. Group one had LBP. Group two (the control group) had no back pain. The goal of the study was to see if patients with LBP flex and extend the spine with the same force and control as healthy subjects.

Isometric muscle contractions were used. This means each person pressed the spine against a resistance without actually moving. A special harness connected to an isometric testing device was used. Both groups used similar force in carrying out the two motions.

The researchers saw a pattern based on the patient's pain level. Patients with more pain took less time to reach the maximum or peak muscle force. They also used a different pattern of muscle action or motor control.

The authors think the differences in motor control for patients with LBP occur as they try to limit pain during motion. It may be possible to use this type of information to see what form of motor control each patient uses. A specific exercise program can be prescribed based on this information.

Martin Descarreaux, MSc, et al. Force Production Parameters in Patients with Low Back Pain and Healthy Control Study Participants. In Spine. February 1, 2004. Vol. 29. No. 3. Pp. 311-317.