Background: Chronic low back pain (LBP) leads to long-term physical and psychological problems and may result in acute deterioration of the pain. It is hypothesized that size changes in selected limb and pelvis muscles during contracting movements are different between healthy individuals and LBP patients.
Materials and methods: A case-control study including two groups of 30 female participants with and without LBP symptoms was designed. Participants were 20-45 years old (36.7±6.7, healthy subjects; 34.6±6.2 LBP subjects). Ultrasonography was used to estimate the thicknesses of the quadratus lumborum (QL), gluteus medius (GMed), transversus abdominis (TrA) and lumbar multifidus (MF). Thickness changes of the muscles in a submaximal contracting position compared to the rest position were measured. Statistical analysis included an independent t-test to determine the significance of differences, and the Kolmogrov-Smirnov two-sample test to evaluate the normality and reliability.
Results: All muscles increased their thickness during contractions. The average increase in LBP subjects was lower than in the healthy subjects. The smaller increase in the muscle thickness of GMed in the LBP group may suggest a weakness because of imbalance in the GMed muscle of LBP patients.
Conclusions: 1. Ultrasonography of local and global muscles is an appropriate device for clinical diagnosis of LBP. 2. Strengthening TrA, MF, and GMed muscles for pain prevention is effective in the prevention and treatment of LBP.
Keywords: gluteus medius; lumbar multifidus muscle; quadratus lumbarum muscle; spinal stability; transversus abdominis muscle.