To study the force-velocity characteristics of human knee-hip extension movement, a dynamometer, in which force was controlled by a servo system, was developed. Seated subjects pressed either bilaterally or unilaterally a force plate, a horizontal position of which was servo-controlled so as to equalize the measured force and a force command generated by a computer at a time resolution of 2 ms (force clamp). The force command was based on the relation between maximum isometric force and foot position within the range between 70% and 90% of "leg length" (LL: longitudinal distance between the sole of the foot and the hip joint), so that the same force relative to the maximum isometric force was consistently applied regardless of the foot position. By regulating the force according to this function, the force-velocity relation was determined. The force-velocity relation obtained was described by a linear function (n=17, r=-0.986 for 80% LL, r=-0.968 for 85% LL) within a range of force between 0.1 and 0.8F(0) (maximum isometric force). The maximum force extrapolated from the linear regression (F(max)) coincided with F(0) (n=17, F(0)/F(max)=1.00+/-0.09 for 80% LL and 1.00+/-0.20 for 85% LL). Also, the velocity at zero force (V(max)) was obtained from the extrapolation. When compared to the bilateral movements, unilateral movements gave rise to a smaller F(max) but the same V(max), suggesting that V(max) is independent of force and therefore represents the proper unloaded velocity. It is suggested that some neural mechanisms may be involved in the force-velocity relation of the knee-hip extension movement, and make it exhibit a linear appearance rather than a hyperbola.

译文

为了研究人体膝关节-髋关节伸展运动的力-速度特性,开发了一种测力计,该测力计由伺服系统控制。就座的对象在两侧或一侧按压一个测力板,其水平位置受到伺服控制,以使测得的力和计算机以2 ms的时间分辨率 (力夹) 产生的力命令相等。力命令基于最大等距力和足部位置之间的关系,范围在 “腿长” 的70% 和90% 之间 (LL: 脚底和髋关节之间的纵向距离),因此,无论脚的位置如何,都始终施加相对于最大等距力的相同力。通过根据此函数调节力,确定了力-速度关系。在0.1和0.8F(0) (最大等距力) 之间的力范围内,通过线性函数 (n = 17,对于80% LL,r =-0.986,对于85% LL,r =-0.968) 描述获得的力-速度关系。从线性回归外推的最大力 (F(max)) 与F(0) 一致 (对于80% LL,n = 17,F(0)/F(max)= 1.00 +/-0.09,对于85% LL,1.00 +/-0.20)。此外,通过外推获得了零力 (V(max)) 的速度。与双边运动相比,单边运动产生的F(max) 较小,但V(max) 相同,这表明V(max) 与力无关,因此代表适当的空载速度。建议某些神经机制可能参与膝髋伸展运动的力-速度关系,并使其表现出线性外观而不是双曲线。

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