Analysis of EMG signals in the Quadratus Lumborum muscle of healthy subject with functional leg length discrepancy

The purpose of this study was to analyze the electromyography (EMG) signals of the Quadratus Lumborum (QL) muscle activity on leg length discrepancy (LLD) and pelvic asymmetry. So we investigated whether pelvic asymmetry might cause injuries in lumbar spine and lower extremity. This was a randomized control experiment, total 50 (25 males and 25 females) datas were analyzed. All participants were right handed. Iliac crest levels were assessed by manually and LLD measurement was used with tape. EMG signals of the QL muscle were taken in the resting position without any activity intentionally in the prone position. Analysis of the data revealed that the QL muscles activity were higher at the pelvic elevation on the right side than on the left side. While there was a shortness in the lower extremity 27% of the cases on the right condition but it was statistically determined that 23% of the left side was short. At the same time, 100% of the cases in the lower extremity on the right side were found to be in the right iliac crest elevation position. Unilateral hyperactivity of the QL muscle leads to instability of the spine and pelvic muscles and causing pelvis asymmetry and functional LLD. As a result, unbalanced loading on the spine and lower extremities may result in injury.