Dapena J
J Biomech. 1986;19(2):147-58. doi: 10.1016/0021-9290(86)90144-2.
Eight highly-skilled hammer throwers were studied using film analysis procedures. The location and velocity of the center of mass (c.m.) of each thrower, hammer and thrower-hammer system were calculated. The vertical component of motion of all three c.m.s followed cyclic patterns with one fluctuation per turn. The fluctuation of the c.m. of the thrower was ahead of that of the hammer by approximately a third of a cycle, and this made the periods of upward vertical acceleration of the system c.m. coincide approximately with the double-support phases. In the horizontal direction, the c.m.s of the thrower and of the hammer followed roughly trochoid patterns as a result of the combination of rotation with forward displacement across the throwing circle. Their rotations were out of synchrony by approximate synchrony with the hammer, or an essentially straight trajectory. The results of this study suggest that the investigation of the hammer throw might be facilitated by the use of a quasi-inertial non-rotating reference frame that follows the general motion of the system c.m. while ignoring its fluctuations within each turn.
使用影片分析程序对8名技术高超的链球运动员进行了研究。计算了每位运动员、链球以及运动员-链球系统质心（c.m.）的位置和速度。所有三个质心的垂直运动分量均呈现出周期性模式，每旋转一圈有一次波动。运动员质心的波动比链球质心的波动提前约三分之一周期，这使得系统质心向上垂直加速的时间段大致与双支撑阶段重合。在水平方向上，由于旋转与在投掷圈内向前位移的结合，运动员和链球的质心大致呈次摆线模式运动。它们的旋转不同步，与链球的旋转近似同步，或者是基本呈直线轨迹。本研究结果表明，使用一个准惯性非旋转参考系可能有助于链球投掷的研究，该参考系跟随系统质心的总体运动，同时忽略其每一圈内的波动。
