Report to the Coaches: Softball Pitching at the 1996 Olympic Games

The time interval from the instant the ball leaves the glove until one-half second after ball release was analyzed. Over fifty parameters related to pitching mechanics were calculated, as were the stresses on the throwing arm. In addition, ball speed was divided into its contributions from the trunk, upper arm, forearm and hand.

RESULTS

It is beyond the scope of this report to document all of the research results, therefore the following section is limited to the most relevant findings. Two main concepts are reviewed, one dealing with injury potential and the other with pitching performance.

Injury Potential

Average data from the 24 Olympic pitchers provided insight into the relationship between pitching mechanics and stress on the throwing shoulder. At the shoulder joint, where most pitching injuries occur, a potentially harmful distraction force occurs as the ball is released. A distraction force is a pull directed along the upper arm pointing toward the elbow joint. This type of force tends to pull the arm away from the shoulder joint. For the Olympic pitchers studied, this force ranged in magnitude from 50 to 150 percent of body weight at ball release. This range is equivalent to 80 to 290 pounds of force (350 to 1275 Newtons). To put this in perspective, in baseball pitching, a skill known to result in many shoulder injuries, a similar distraction force equal to a pitcher's body weight is also found near ball release.

It appears that the distraction force at the shoulder joint is greatly affected by pitching mechanics. Trunk rotation, position of the throwing arm as the stride foot comes into contact with the ground, stride length and position, and throwing arm position at the instant of ball release are important. Seven specific parameters related to pitching mechanics are depicted graphically in the following pages. These seven measurements: 1) shoulder extension at stride foot contact, 2) shoulder abduction at stride foot contact, 3) knee angle at stride foot contact, 4) stride length, 5) stride angle, 6) elbow angle at release and 7) hip angle at release are important predictors of shoulder stress.

Two terms used throughout this report that may be unfamiliar to some readers are shoulder extension and shoulder abduction. The following figure depicts these shoulder angles:

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