Relations of Bilateral Symmetry in the Cross-sectional Area of the Quadratus Lumborum Muscles to Posture in the Frontal Plane and Respiratory Function in Forced Breathing

Abstract

[Purpose] The purpose of this study was to investigate the relations of bilateral symmetry in the cross-sectional area of quadratus lumborum muscles with frontal posture and respiratory function. [Subjects and Methods] The subjects were 20 healthy males. Measurement items comprised the cross-sectional area of the quadratus lumborum muscles, frontal posture, thoracic extension rate, respiratory muscle strength, and pulmonary function. [Results] Bilateral asymmetry was observed in the cross-sectional area of quadratus lumborum muscles; the mass of the right quadratus lumborum muscle was larger than that of the left quadratus lumborum muscle. Significant positive correlations were found between bilateral symmetry of the cross-sectional area of the quadratus lumborum muscles and frontal posture, thoracic extension rate, and expiratory muscle strength; and there was a significant negative correlation with the pulmonary function index of residual volume. [Conclusion] The present study revealed relationships between bilateral symmetry in the cross-sectional area of the quadratus lumborum muscles and frontal posture and respiratory function.