This study investigated the relationships among thoracic lateral deviation, asymmetry of the thoracic shape, and asymmetry of the lateral tilt angle of the shank in the stance phase of gait. [Participants and Methods] The participants were 18 healthy males. The measurement items were the thoracic lateral deviation and asymmetry of the thoracic shape at standing rest, and the change of the outer tilt angle of the shank in the stance phase of gait. The cohort was divided into an all subjects group (n=18), a left deviation group (n=15), and a right deviation group (n=3) based on the degree of thoracic lateral deviation. [Results] In the all subjects group, the change of the outer tilt angle of the shank was significantly larger on the right side than on the left side in the early stance phase, and the same significant difference was observed in the left deviation group in both the early and late stance phases. In the late stance phase, the change of the outer tilt angle of the shank negatively correlated with the thoracic lateral deviation and positively correlated with the asymmetry of the lower thoracic shape. [Conclusion] These results suggest that increases of thoracic lateral deviation and asymmetry of the lower thoracic shape elicit greater outward movement of the shank on the right side.

This study investigated the relationships among the lateral deviation of the thorax, crosssectional area of the psoas major muscle, and left-right asymmetry of the pelvic rotation angle. [Participants and Methods] The participants were 17 healthy males. The cross-sectional area of the psoas major muscle and change in pelvic rotation angle during isometric hip flexion were measured. [Results] The cross-sectional area of the psoas major muscle was significantly larger on the right and the change in the pelvic rotation angle to the ipsilateral side was significantly larger on the left. Furthermore, there was a significant negative correlation of the amount of lateral deviation of the thorax with the ratio of the left and right psoas major muscle cross-sectional areas, and a significant positive correlation with the ratio of the left and right pelvic rotation angles. [Conclusion] The results suggest that it is important to assess lateral deviation of the thorax in the upright position to evaluate changes in the cross-sectional area of the psoas major muscle during isometric hip flexion.

[Purpose] This study aimed to determine the relationship between thoracic lateral deviation, the bilateral ratio of the thoracic shape, and the bilateral ratio of the thoracic and lumbar iliocostalis muscles during resting sitting and thoracic lateral translation. [Participants and Methods] We included 23 healthy adult males in the study. The measurement tasks were resting sitting and thoracic lateral translation relative to the pelvis. The thoracic lateral deviation and bilateral ratio of the upper and lower thoracic shapes were measured using three-dimensional motion capture. The bilateral ratio of the thoracic and lumbar iliocostalis muscles were measured using the surface electromyographic recording. [Results] The bilateral ratio of the lower thoracic shape was significantly positively correlated with the thoracic translation distance and the bilateral ratio of the thoracic and iliocostalis muscles. In addition, the bilateral ratio of the thoracic iliocostalis muscles was significantly negatively correlated with the bilateral ratios of the lower thoracic shape and lumbar iliocostalis muscles. [Conclusion] Our findings showed that the asymmetry of the lower thoracic shape is associated with left lateral deviation of the thorax at rest and thoracic translation distance. In addition, the thoracic and lumbar iliocostalis muscle activity differed between the left and right translations.

We aimed to investigate the relationship of thoracic asymmetry in standing position with asymmetry of the internal ankle moment in the frontal plane during gait. [Participants and Methods] The following measurements were recorded in 22 healthy adult males using a 3D motion analyzer and force plates: thoracic lateral deviation, asymmetrical ratios of the upper and lower thoracic shape, internal ankle moment in the frontal plane, mediolateral deviations of the center of mass and center of pressure. [Results] In the standing position, the thorax was deviated to the left relative to the pelvis, and the upper and lower thoracic shapes were asymmetrical. During gait, significant lateralities were observed in the internal ankle moment in the frontal plane, mediolateral deviations of the center of mass and the center of pressure. Significant positive correlations were observed between the asymmetrical ratio of the lower thoracic shape and both the asymmetry of the internal ankle moment in the frontal plane and the mediolateral deviation of the center of pressure. [Conclusion] These results suggest that thoracic asymmetry is associated with mediolateral control of the ankle during gait.