Analysis of the quadratus lumborum muscle activity on leg length discrepancy: A randomized controlled trial

BACKGROUND: Quadratus lumborum (QL) discrete region extensions might change depending on whether leg length discrepancy (LLD) individually has any extra erector spinae action in the lumbar spine, which can result in serious injury to the lower extremities and lumbar vertebrae. OBJECTIVE: This study aims to investigate the effect of QL muscle activity on LLD by using electromyography (EMG) signals. METHODS: The study employed a randomized controlled design. A total of 100 right-handed volunteers were included in this study. All participants were assessed manually by tape measurement for LLD. EMG signals were recorded during the resting and maximal isometric contraction positions to determine QL muscle activity. The power spectral density (PSD) methods were applied to compute EMG signals. RESULTS: In maximal isometric contraction position, comparing the short right LLD (Right side = 0.00064 +/- 0.00001, Left side = 0.00033 +/- 0.0006) and short left LLD (Right side = 0.00001 +/- 0.00008, Left side = 0.00017 +/- 0.0001), it was found that the short right LLD group had significantly increased PSD of EMG values. In resting position, the short right LLD (Right side = 0.0002 +/- 0.0073, Left side = -0.00016 +/- 0.0065) had significantly increased PSD of EMG compared to the short left LLD (Right side = 0.00004 +/- 0.0003, Left side = 0.0001 +/- 0.0008) values of the QL muscle activity. The results of both groups were also statistically significant (p < 0.05). CONCLUSIONS: The present study showed that it is possible to determine effective experimental interventions for functional LLD using EMG signal analysis of QL muscle activity on an asymptomatic normal population.