Dapena J, McDonald C
Department of Physical Education, Indiana University, Bloomington 47405.
Med Sci Sports Exerc. 1989 Apr;21(2):206-20.
Eight hammer throwers were studied using three-dimensional cinematography. The local term of angular momentum of each thrower (HTL) followed a wide conical path, while the remote term (HTR) and the hammer angular momentum (HH) followed much narrower conical paths. HT, the sum of HTL and HTR, followed a conical path similar to that of HTL, although with smaller amplitude. HH was half of a cycle out of phase with HT. It was also larger but followed a narrower conical path. As a result, the conical paths of HH and HT counteracted each other, and HS, the total angular momentum vector of the thrower-hammer system, had little conical motion. The paths of the angular momentum vectors, the trunk tilt, and the height of the hammer plane relative to the system center of mass were interrelated. Some throwers kept the hammer plane high and the trunk tilting back in all the turns; other throwers kept the hammer plane low and the trunk tilting forward in the early turns, but the hammer plane rose in their late turns and the trunk tilted back. Two theories were proposed to explain why the athletes who had forward trunk tilt in the early turns tilted backward in the final part of the throw.
使用三维摄影技术对8名链球运动员进行了研究。每个运动员的局部角动量（HTL）遵循一条宽阔的锥形路径，而远端角动量（HTR）和链球角动量（HH）遵循的锥形路径则窄得多。HT是HTL和HTR之和，遵循与HTL相似的锥形路径，尽管幅度较小。HH与HT相差半个周期。它也更大，但遵循的锥形路径更窄。结果，HH和HT的锥形路径相互抵消，运动员-链球系统的总角动量矢量HS几乎没有锥形运动。角动量矢量的路径、躯干倾斜度以及链球平面相对于系统质心的高度是相互关联的。一些运动员在所有旋转过程中都保持链球平面较高且躯干向后倾斜；其他运动员在早期旋转中保持链球平面较低且躯干向前倾斜，但在后期旋转中链球平面上升且躯干向后倾斜。提出了两种理论来解释为什么在早期旋转中躯干向前倾斜的运动员在投掷的最后部分会向后倾斜。
