Motor control exercises for patients with low back pain

Abstract

Exercise therapy can reduce pain and improve function for persons with nonspecific low back pain. However, it is not clear which type of exercises is most effective. The mechanisms underlying chronic nonspecific low back pain and effect of exercises are poorly understood. Pain-induced adaptations in motor control of trunk muscles, especially delayed and reduced activity in transversus abdominis, have been suggested to contribute to persistent low back pain. Fear-avoidance beliefs also seem to be related to chronic pain, by avoidance of activity and possibly by altered motor behaviour. Motor control exercises are based on a hypothesized causal relation between impaired trunk motor control and chronic low back pain. In this study the effect of low-load motor control exercises, high-load sling exercises and general exercises was compared for patients with low back pain. Whether deep abdominal muscle activation was linked to long-term low back pain reduction and to fear-avoidance beliefs was also explored.

The aim of the first two studies was to compare pain, deep abdominal muscle onset, disability, and fear-avoidance beliefs after motor control exercises, sling exercises and general exercises for low back pain. A randomized controlled trial with one year followup was performed in a primary care setting in Trondheim, Norway. A total of 109 patients with chronic nonspecific low back pain were randomized and participated in exercise therapy once a week for eight weeks. Pain was reported before and after treatment and at one year follow-up. Onset of deep abdominal muscles in anticipation of rapid shoulder flexion, self-reported activity limitation, fingertip-to-floor distance, and fear-avoidance beliefs were registered before and after intervention. Assessment after intervention showed no significant differences between groups with respect to pain, selfreported activity limitation, fingertip-to-floor distance, or fear-avoidance beliefs. Participants in the sling exercise group achieved faster abdominal onset on one side. Overall, there were small changes in abdominal muscle onset and there were no associations between changes in onset and changes in pain over the intervention period

The aim of the third study was to investigate associations between deep abdominal muscle activation and long-term low back pain. Activation timing and level of the deep abdominal muscles were recorded before and after 8 weeks with exercises for the patients included in the randomized controlled trial. Pain was registered before and one year after intervention. Associations between muscle activation and long-term pain were examined by multiple linear and logistic regression methods. An association between ability to activate transversus abdominis, measured by slide of the muscle, and odds for long-term pain reduction was found. Improved transversus abdominis slide among participants with low baseline slide was associated with clinically important long-term pain reduction. Otherwise, there were no, or marginal, associations between deep abdominal muscle activation and low back pain.

The aim of the fourth study was to investigate associations between fear-avoidance beliefs at baseline and deep abdominal muscle activation after exercise therapy. As in study 3, the cohort of patients enrolled in the clinical trial was studied longitudinally. Associations between baseline fear-avoidance beliefs and deep abdominal muscle activation after exercises were analyzed with multiple linear regression methods. Some negative association between fear-avoidance beliefs for physical activity before intervention and transversus abdominis recruitment measured by slide after intervention was found. No other significant associations between fear-avoidance beliefs and abdominal muscle activation were found.

This study gave no basis to recommend any of the studied exercise interventions over the others in the treatment of persons with chronic nonspecific low back pain. The observation of a long-term relation between transversus abdominis recruitment and low back pain is new and should be sought reproduced. If replicated, results from study 4 might mean that for apprehensive patients, intervention should aim at reducing fear before, or in parallel with, improving neuromuscular control.