FIBER-TYPE CHARACTERISTICS OF THE LUMBAR PARASPINAL MUSCLES IN NORMALHEALTHY-SUBJECTS AND IN PATIENTS WITH LOW-BACK-PAIN

A knowledge of the alteration in the fibre type profile of paraspinal muscle associated with low back pain is essential for the design of su ccessful rehabilitation programmes. In attempting to compare the muscl es of patients with low back pain with those of controls, few previous studies have considered factors such as gender, age, and size of the subjects, each of which can potentially confound interpretation of the results. We obtained samples of lumbar paraspinal muscle during spina l surgery from 21 patients with low back pain and, using the percutane ous biopsy technique, from 21 control volunteers matched for gender, a ge, and body mass. The samples were subject to routine histochemical a nalysis to determine characteristics of muscle fibre type. Compared wi th controls, the muscle of the patients had a significantly higher pro portion of type-IIB (fast-twitch glycolytic) fibres than type-I (slow oxidative) fibres. The mean size of a given fibre type did not differ between the patients and the controls. Consequently, the relative area of the muscle occupied by type-IIB fibres was higher and that by type -I fibres was lower in the patients. The patients had a greater number of muscle samples with more than 1% type-IIC fibres, and abnormalitie s that could be described as pathological were more marked in the pati ents than in the controls. In conclusion, the paraspinal muscles of pa tients who have low back pain display a more glycolytic (faster) profi le; this can be expected to render them less resistant to fatigue.