其他摘要：The purpose of this study was to measure the degree of stability of Various standing postures when external force was applied to the body. The subjects (16 healthy adults) were asked to resist against an external force with a maximum effort in nine different defensive postures. These postures were divided into two groups: one in which the hip or knee joints or both were flexed and the other with the feet spread apart in different positions. A rope was wound to the chest of the standing subject. The other end of the rope was attached to a winch which was rotated electrically at the desired speed. The rope was pulled at speeds of 10.6, 32.3, 53.7, 76.8 and 105.4cm/sec, respectively. The rope was pulled continuously at a uniform rate until the subject could not maintain his initial position. The tensile force of the rope was measured with a semiconductive strainmeter. The maximum tensile force of the rope represents the maximum resistant force exertet by the subject against the external force. Quadratic equations between the maximum resistant force and the pulling speed were determined by the least squares method in the rigid body. Y = a_0 + a_1V + a_2V^2 (Y : the maximum resistant force; kg., V: the pulling speed; cm/sec) (0 < V < 105.4). The same relationship was found in an erect posture with a closed stride position for each subject. Although a relationship was found in the other postures in which the higher the pulling speed, the greater the resistant force, the quadratic equations could not be obtained. The most stable posture was a crouching one with one foot in front of the other and the least stable posture was an erect one with a closed stride position at all speed. For the most stable posture, (make the resistant force greatest) the position with the knee and hip joints flexed was more effective than that with the feet spread. As a conclusion, the muscular activity has a large influence on the stability in the human standing posture in addition to the mechanical principles.
