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An athlete was filmed at high speed to anatomically plot the position of the vertebrae during several pole vaults. A computer analysis adapted from a previously described program (Gainor, BJ, et al: The kick: Biomechanics and collision injury. Am J Sports Med 6: 185-193, 1978) was used to quantify the kinematic data. The thoracic and lumbar vertebrae of the polevaulter began in a neutral position but rapidly hyperextended 40 degrees during pole plant. The spine subsequently flexed 130 degrees in 0.65 seconds as the pole uncoiled and the athlete was propelled towards the bar. Angular velocities of the spine reached a maximum of 6 radians/sec during both extension and flexion. More significantly, angular accelerations of 150 radians/sec2 occurred in hyperextension, and 180 radians/sec2 in hyperflexion. Torque about the spine was estimated to be 1,500 inch-pounds during extension and 1,800 inch-pounds during flexion. The maximum kinetic energy in the athlete's body was calculated to be 36,000 inch-pounds. We believe the magnitude of these torques and accelerations predispose the back to injury. These results were correlated with several cases of spondylolysis in competing polevaulters.

Twenty-six cases of waterskiing-related injuries, including four deaths, were studied and the case histories classified into four categories. Injury was caused by a fall into unobstructed water, by boat propeller blades, by collisions with obstacles or a boat, and by the tow rope. Injuries sustained in falls were comparable to trauma seen in vigorous contact sports. Boat propeller blades inflicted devastating battlefield-type wounds, and collisions produced trauma similar to that seen in motor vehicle accidents. The shearing action of an accelerating tow rope imparted trauma unique to this sporting activity. There is limited recognition of the potential for serious injury that attends this recreational sport, and it is concluded that the prevention of injury depends on the nuclear trio of participants: boat operator, operator, observer, and skier.

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.