Muscles rarely contract one at a time. When one muscle contracts, the opposite muscle must relax or contract at the same time. In the trunk, groups of muscles work together to hold the back upright. The same is true during movement. In fact, these muscles have a certain pattern to their work together.
These patterns are called trunk muscle recruitment patterns (TMRPs). Researchers think TMRPs are different in patients with low back pain than in adults without back pain. Patterns of muscle recruitment in both groups are the subject of this study.
Many studies have been done to show the level of muscle action with back movements. This study looks at patterns of muscle action during tasks such as bending forward, bending sideways (right and left), and extending backwards. Sixteen adults with chronic low back pain of unknown cause and 16 healthy adults were compared.
The authors say that the differences in the two groups points to a TMRP that tries to increase spinal stability in the subjects with back pain. The muscles appear to be trying to make up for a loss of stability. Or it could be that an increased amount of muscle activity is needed because back muscles have begun to shrink (atrophy) in patients with back pain.
Whatever the cause, it’s clear there are changes in TMRPs for patients with chronic low back pain. These changes may even persist after the pain is gone. Therapists working with back pain patients to restore normal muscle activity must be careful. There may be some TMRPs that are still needed to hold the spine stable.