The effects of lumbar extensor strength on disability and mobility in patients with persistent low back pain

BACKGROUND: It is assumed that low back pain patients who use pain-avoiding immobilizing strategies may benefit from specific back flexion and extension exercises aimed at reducing sagittal lumbar hypomobility. The aim of this study was to test this potential working mechanism in chronic low back pain patients undergoing lumbar extensor strengthening training. METHODS: A single-group prospective cohort design was used in this study. Patients with persistent low back complaints for at least 2 years were recruited at a specialized physical therapy clinics center. They participated in a progressive 11-week lumbar extensor strength training program, once a week. At baseline, sagittal lumbar mobility in flexion and extension was measured with a computer-assisted inclinometer. Self-rated pain intensity was measured using a visual analogue scale, back-specific functional status was assessed with the Quebec Back Pain Disability Scale and the Patient Specific Complains questionnaire. RESULTS: Statistically significant improvements were found in pain (28% decrease) and functional disability (23% to 36% decrease). Most progress was seen in the first 5 treatment weeks. Lumbar mobility in flexion showed non-significant increases over time (+ 12%). Pre-post treatment changes in flexion and extension mobility did not contribute significantly to the models. The retained factors together explained 15% to 48% of the variation in outcome. CONCLUSIONS: Specific lumbar strengthening showed clinically relevant improvements in pain and disability in patients with persistent chronic low back pain. These improvements did not necessarily relate to improvements in lumbar mobility. Parameters representing other domains of adaptations to exercise may be needed to evaluate the effects of back pain management.