Clinically, we all have seen a subgroup of individuals with low back pain who get better with our treatment but return to our care within a few months due to a reoccurance of symptoms. I often question: Why does this happen? Is it a muscular imbalance? Is it an altered pain perception? Is it a combination? What is predisposing these individuals for pain and keeping them coming back into my office?
MacDonald et al attempted to answer these questions by identifying why certain patients have a higher reoccurance rate of low back pain . They did this by investigating whether neuromuscular control of the short and long fibers of the deep back muscles differs in patients who have a history of unilateral low back pain, who currently are asymptomatic, versus healthy counterparts. They did this by looking at the EMG activity of the short and long fibers of the multifus and shoulder musculature and compared the two groups and found:
- EMG onset of the short fibers of the deep back musculature relative to the deltoid (in the shoulder) occured later in people with recurrent LBP than in their healthy subjects.
- This delay was higher on the previously painful side of the low back as compared to the non-painful side.
- The timing of muscle activation (short fibers active before long fibers) was observed in both healthy individuals and on the non-painful side in the pain group, but absent on the previously painful side. The alteration in timing may reflect changes in motor planning which could be due to inaccurate or ignored sensory information from the spine OR a change in strategy by the central nervous system. This actually may be a way of attempting to avoid pain provocation.
- Impared control of these muscles likely will compromise spinal control and likely makes the spine more vulnerable for recurrent episodes of pain.
MacDonald D, Moseley GL, Hodges PW. Why do some patients keep hurting their back? Evidence of ongoing back muscle dysfunction during remission from recurrent back pain. Pain 2009; 142: 183-188.