It is important to quantify the postural stability. The frame subtraction method can calculate the motions of a subject, and might be easier to implement, with lower costs. However, validity of the evaluation of postural stability using this method have not been validated yet. Therefore, the purpose of this study was to verify criterion-related validity of the frame subtraction scores and the COP parameters during maintenance of single leg standing.

Twenty two healthy young subjects participated in this study. Motion tasks comprised right leg standing with eyes open and closed. The total length of COP displacements (LNG), Root mean square (RMS) area, AP (anterior - posterior) range , ML (medial - lateral) range were recorded using the force plate. Simultaneously, the motion images were acquired with digital video cameras from the front and right sides. After the motion images were analyzed using the frame subtraction method, the frame subtraction scores (maximum / sum of the frame subtraction score on each plane / the frontal and sagittal planes) were measured. To confirm the validity, Spearman’s rank correlation coefficient between the frame subtraction scores and the COP parameters was calculated.

The sum of the frame subtraction score on the frontal plane was significantly correlated with all COP displacements in the single leg standing. The result of this study indicated that the frame subtraction method could be applied to the evaluation of balance task with postural sway such as maintenance of single leg standing. The frame subtraction method is low cost and easy owing to its marker-less systems.

量化姿势稳定性很重要。帧减法可以计算对象的运动，并且可能更容易实现且成本更低。但是，使用这种方法评估姿势稳定性的有效性尚未得到验证。因此，本研究的目的是验证单腿站立维持过程中框架减分得分和COP参数与标准相关的有效性。

22名健康的年轻受试者参加了这项研究。运动任务包括右腿站立时睁开和闭上眼睛。使用测力板记录COP位移（LNG）的总长度，均方根（RMS）面积，AP（前后）范围，ML（内侧-外侧）范围。同时，使用数码摄像机从正面和右侧采集运动图像。在使用帧减法分析运动图像之后，测量帧减法分数（每个平面/额叶和矢状平面上的帧减法分数的最大值/总和）。为了确认有效性，计算了帧减分和COP参数之间的Spearman秩相关系数。

额叶上框架减分的总和与单腿站立时所有COP位移均显着相关。研究结果表明，框架减影法可用于姿势摆姿势的平衡任务评估，如保持单腿站立。帧减法由于其无标记系统而成本低且容易。