Effects of Directional Change on Postural Adjustments during the Sit-to-walk Task.

[Purpose] The purpose of this study was to clarify the effects of directional change on postural adjustments during the sit-to-walk (STW) task. [Subjects] Fifteen healthy young men participated in this study. [Methods] Subjects were required to stand up from a chair and walk toward a target. The first step was limited to the right limb only. Three conditions of target direction (straight, ipsilateral and contralateral) were set. For the ipsilateral and contralateral conditions, the target was placed at an angle 45° clockwise and 45° counterclockwise from straight ahead, respectively. Trials were recorded by a motion capture system and force plates. The forward momentum of the body, time of events, center of pressure (COP) and center of gravity (COG) displacement were measured and compared between conditions. [Results] In the contralateral condition, the fluidity index was significantly lower than that in the straight condition. In the contralateral condition, COP displacement toward the swing limb was larger than in the other conditions. [Conclusion] The present results indicate that a directional change during the STW task affects fluidity and postural adjustments. When the STW direction was changed to diagonal, the lateral component of postural control became more important.