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[Purpose] To investigate whether postures of the head and trunk in the frontal plane affect the subjective visual vertical (SVV). [Subjects] Nineteen healthy adults were enrolled. [Methods] We measured SVV under five sitting conditions: upright, inclining the head, inclining the trunk, inclining the trunk with the head upright, inclining both the head and trunk. Subjects were instructed to stop a moving line on a PC monitor when they thought that the line was vertical. The values of SVV, and the differences in degree between the true vertical and subjective vertical, were compared among the five conditions. [Results] The absolute values of SVV in the upright and inclining the trunk with the head upright conditions were significantly smaller than those in the three other conditions. The values of SVV in the inclining the trunk condition was significantly smaller than those in the inclining the head or in inclining the head and trunk conditions. [Conclusions] The effects of posture on SVV measurement must be considered. [ABSTRACT FROM AUTHOR]

[Purpose] The aim of this study was to investigate whether exploratory factor analysis could classify the patterns of joint motions during a task of lateral dynamic sitting balance. [Subjects] Forty-eight healthy adults (29 males and 19 females) were recruited for this study. [Method] We measured the center of pressure (COP) and joint motions during maximal lateral weight shift in sitting. The joint motions were classified with exploratory factor analysis. Furthermore, we used multiple regression analysis to examine which factors were significantly related to the amount of COP displacement. [Results] We found that the joint motions were classified into 4 types of pattern by the exploratory factor analysis (accumulated contribution ratio=42.5%). The main factors extracted by multiple regression were factors that were related to postural reaction. [Conclusion] Exploratory factor analysis could classify joint motions and could objectively evaluate movement patterns during a task of lateral dynamic sitting balance. [ABSTRACT FROM AUTHOR]