Gainor B J, Piotrowski G, Puhl J, Allen W C, Hagen R
Am J Sports Med. 1980 Mar-Apr;8(2):114-8. doi: 10.1177/036354658000800210.
The throw and its modifications are integral components of many sports. This study correlates case histories of acute injuries in throwing with a biomechanical analysis of the throwing mechanism. Comparisons are made with a similar analysis of the kick analyzed by the same film technique and computer program. Just prior to ball release, the pitching arm extends through an arc of about 73 degress in 40 msec, beginning with the elbow flexed at 80 degrees. This produces an axial load on the humerus and coincides with a pulse of external torque at the shoulder. This acts as stress protection to the humerus which is developing an internal torque of 14,000 inch-lb prior to ball release. The change in angular velocity, or the angular acceleration, during the throw is acquired in a much shorter time than in the kick. Torque is directly proportional to angular acceleration. This necessitates the development of substantially higher torques in the humerus during the throw than about the knee during a kick. The kinetic energy in the arm is 27,000 inch-lb during the throw. This is much higher than the kinetic energy in the kicking leg because the kinetic energy varies proportionally with the square of the angular velocity of the extremity. The angular velocity of the arm is about twice that of the leg. Thus, the pitching arm contains about four times as much kinetic energy as the kicking leg. These severe overloading conditions predispose the upper extremity to injury in the throwing mechanism.
投掷动作及其变体是许多体育运动的重要组成部分。本研究将投掷急性损伤的病例史与投掷机制的生物力学分析相关联。并采用相同的影片技术和计算机程序对踢腿动作进行类似分析，以作比较。在即将投出球之前，投球手臂在40毫秒内通过约73度的弧度伸展，起始时肘部弯曲80度。这会在肱骨上产生轴向负荷，同时在肩部出现一个外部扭矩脉冲。这对肱骨起到了应力保护作用，在投出球之前肱骨正在产生14,000英寸 - 磅的内部扭矩。投掷过程中角速度的变化，即角加速度，比踢腿动作在更短的时间内获得。扭矩与角加速度成正比。这就使得在投掷过程中肱骨所产生的扭矩要比踢腿时膝关节处的扭矩高得多。投掷过程中手臂的动能为27,000英寸 - 磅。这远高于踢腿腿部的动能，因为动能与肢体角速度的平方成正比。手臂的角速度约为腿部的两倍。因此，投球手臂所包含的动能约为踢腿腿部的四倍。这些严重的过载情况使上肢在投掷机制中容易受伤。
