Study design: Trunk muscle strength and the effect of trunk muscle exercises on chronic low back pain were investigated in patients with chronic low back pain.
Objective: Patients with chronic low back pain include those with organic lumbar lesions and those without such lesions. This study analyzed the differences in trunk muscle strength and effect of trunk muscle exercises between these two groups of patients.
Summary of background data: Previous studies have reported lower trunk muscle strength in patients with chronic low back pain and higher efficacy of trunk muscle exercises for treating chronic low back pain. However, no analysis have yet been done of differences in these parameters between patients with chronic low back pain with and without organic lumbar lesions.
Methods: One-hundred-twenty-three patients with chronic low back pain and 126 healthy individuals without low back pain (control group) underwent trunk muscle strength evaluation. The patients were further divided into two groups-- those in group 1 had detectable organic lumbar lesions and those in group 2 had no detectable organic lesions. Seventy-two of these patients performed trunk muscle exercises and the correlation between improvement in low back pain and increase in trunk muscle strength was analyzed.
Results: Trunk flexor and extensor strengths were significantly lower in both groups. However, the flexor/extensor ratio of maximum torque was significantly higher in group 1 than in the control group, but was not significantly different between group 2 and the control group. Trunk muscle exercises reduced low back pain in both groups, but were more effective in group 2 than in group 1. The degree of correlation between increase in trunk muscle strength and improvement of low back pain also was higher in group 2 than in group 1.
Conclusion: This difference in flexor/extensor ratio may have been due to reduced extensor strength resulting from neurogenic muscle weakness induced by the organic lumbar lesions in group 1. The exercise-associated increase in trunk muscle strength did not completely eliminate the low back pain induced by the organic lumbar lesions in group 1. However, increasing trunk muscle strength was extremely effective in patients of Group 2, in which decreased trunk muscle strength was a major factor in chronic low back pain.