Gait asymmetry characteristics: relationship between lateral deviation of the thorax in the standing position and asymmetry indices during gait.

[Purpose] This study aimed to determine whether a common left-right asymmetry exists in frontal plane movement during gait and to explore its relationship with resting standing posture. [Participants and Methods] Twenty-five healthy adult male participants with no history of surgery were assessed during standing and gait using a three-dimensional motion analysis system. The maximum lateral movement of the trunk and center of mass, peak of the vertical ground reaction force, and lateral position of the center of pressure were compared between the left and right stance phases. The relationship between asymmetry in standing posture and gait was also evaluated. [Results] Most participants exhibited a leftward thoracic deviation relative to the pelvis while standing. During gait, lateral movement of the center of mass, first peak of the vertical ground reaction force, and lateral position of the center of pressure were all significantly greater during the left stance phase compared with the right. Additionally, greater leftward thoracic deviation in the standing posture was associated with larger asymmetry in lateral trunk and center of mass movement during gait. [Conclusion] A consistent left-right asymmetry was observed in both resting standing posture and gait. Leftward thoracic deviation in standing appears to shift the center of mass to the left during gait, potentially contributing to inefficient gait patterns.