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Journal of Orthopedic Science
2000 Volume 5, Number 3
Department of Orthopaedic Surgery, Kochi Medical School, Kohasu, Oko-cho, Nankoku, Kochi 783, Japan

Previous studies of trunk muscle strength in patients with chronic low back pain (CLBP) have mainly reported on patients aged younger than 40 years. However, no such investigation has yet been done in middle-aged patients. Trunk muscle strength and the effect of trunk muscle exercises were investigated in patients with CLBP aged more than 40 years. Trunk muscle strengths were measured in a LBP group (52 patients) and a control group (60 volunteers) and the results for the two groups were compared. The LBP group was divided into three subgroups. Group A had only age-related spondylosis and group B had disk herniation and spondylolisthesis with age-related spondylotic change. Both these groups were able to continue exercises. Group C was made up of patients who had abandoned the exercise program. Trunk muscle strength and symptoms were assessed in each group. Both flexion and extension strength were decreased in the LBP group compared with the control group, with the reduction in extension strength being most marked. In both groups A and B, muscle strength increased and clinical symptoms improved. In contrast, no change was seen in group C. In older patients with CLBP, reduction of muscle strength was more marked in the spinal extensors than in the spinal flexors. It was confirmed that trunk muscle strengthening exercises are useful for increasing muscle strength and improving symptoms in such patients.

Study Outcomes & Clinical Relevance: Like many other recent studies, this study confirms the importance of strengthening the lumbar extensors to improve symptoms in patients with chronic low back pain. Rectus abdominis strength is not compromised to the same degree in such patients and thus should be prioritized accordingly. Other contemporary studies fail to support the outdated notion that weak abdominals are of primary concern in the cause or treatment of low back pain.