Softball

Softball

Biomechanics and Injury Rates in Windmill Softball Pitching

Barrentine SW, Fleisig GS, Whiteside JA, Escamilla RF, Andrews JR. Biomechanics of Windmill Softball Pitching With Implications About Injury Mechanisms at the Shoulder and Elbow. Journal of Orthopaedic & Sports Physical Therapy 28(6):405-414, 1998.

Fleisig GS, Milliron K, Kempf C, Wolforth J. Special Delivery: exploring the mechanics of softball pitching. Sports Medicine Update 16(4):16-18, 2002.

Methods

Dr. Glenn Fleisig of ASMI and others studied the windmill pitching motion via questionnaires and biomechanical analysis. The questionnaires were used collect information on demographics, pitch counts, injuries, and other problems over a one-year period. 321 female pitchers, ranging in age from 8.0 to 23.2 years of age (mean = 13.8), completed the questionnaire. Biomechanical analysis was achieved by using four high-speed (200 frames per second) infrared cameras that recorded the pitching motion of eight college windmill pitchers. The pitching motions were digitized, and the kinematic (angle and velocity) and kinetic (torques and forces) data was analyzed.

Results

During the pitching motion, the windmill pitcher first pushes off the rubber with the shoulder in a hyperextended position. The shoulder is flexed forward and beyond 180° into an extended position. From this position, the ball is accelerated forward by rotation of the trunk, arm, and shoulder and flexion of the elbow. The shoulder adducts and internally rotates as forward flexion of the shoulder reaches a maximum velocity of approximately 5000°/sec. Maximum rotational velocity of the pelvis and upper torso are also achieved at this point. As the arm flexes forward, the elbow extends fully and then flexes with maximum elbow flexion torque occurring at the time of ball release. Maximum internal rotation (4000°/sec) also occurs just before ball release. Deceleration then occurs after ball release with extension torque at the shoulder slowing down arm movement.

Throughout this 485° circumduction, significant stresses are placed on the elbow, shoulder, and other parts of the body. Distraction of the arm, which peaks during the acceleration phase of windmill pitching, is resisted by the shoulder and elbow with forces equal to 98% and 67-69% of body weight respectively. This force along with elbow flexion may make the bicep tendon labrum complex susceptible to overuse injury. The loads created during acceleration and deceleration of the arm may also produce overuse injuries.

Questionnaires examined in the study by Fleisig and others further indicate that overuse injury of the windmill pitcher is a real concern. 30% (90 of 321) of pitchers surveyed suffered an injury causing them to modify their play or miss time. The most commonly reported injury areas were the shoulder (11.2%) and back (7.8%), followed by the upper arm/biceps and the knee (3.4% each). About 30% (96 of 321) reported that pain affected or limited their pitching. Medical care was sought by 19.3% of the athletes, but only 2% required surgery. Over 50% (164 of 321) of the pitchers estimated that they threw an average of 4300 pitches a year.

The forces and torques generated by the windmill pitching motion are significant, and when performed at the high pitch counts reported by these pitchers, they can cause overuse injury. Physical conditioning programs specific to softball help to reduce injury risk. Further attention should also be given to pitching biomechanics, pitch counts, and the number of pitching appearances made by an athlete.