THE EFFECT OF CHRONIC LOW BACK PAIN ON THE SIZE AND ACTIVATION OF THE LUMBAR MULTIFIDUS MUSCLE

The lack of control of lumbar stability is thought to be a major factor in the aetiology and chronicity of low back pain. The lumbar multifidus muscle is considered to play a significant role in maintaining lumbar stability and stiffness. The aim of this study was to use clinical measures to compare lumbar multifidus muscle in chronic low back pain patients and unimpaired subjects. Sixteen subjects with chronic low back pain and 16 unimpaired subjects were assessed in the study. Cross-sectional area (CSA) and contraction size of multifidus were measured on both sides and at individual vertebral levels, from L2 L5, using realtime ultrasound. The differences between the chronic back pain and unimpaired groups were statistically significant for both cross-sectional area and contraction size measures. In the unimpaired group, the contraction size of multifidus was greatest at the L5 segmental level, and then decreased in size at higher lumbar levels. In the chronic low back pain group, the contraction size was the same at L4 and L5 levels and contractions were less at these levels than those at L2 and L3. Three way interactions showed a significant interaction (