April 20, 2009

‘Windmill’ pitching linked to bicep injury

The windmill pitching motion may explain the high incidence of anterior shoulder pain seen in female softball players, U.S. researchers said.

The conventional belief has been that the underhand throwing motion of softball places little stress on the arm, lead author Dr. Nikhil Verma of the Rush University Medical Center in Chicago said in a statement. But that is not the case.

The study involved seven women -- three collegiate and four professional pitchers -- who underwent motion analysis and surface electromyography to evaluate the muscle firing pattern of their biceps in the course of a windmill pitch. Electromyography detects electrical potential generated by muscle cells when they contract.

The study, published in the American Journal of Sports Medicine, found that even though the upper arm movement in both baseball and fast-pitch softball gives the ball about the same velocity, muscle force during the windmill pitch was much higher.

Moreover, the maximum force, or maximum contraction, occurred not when the arm was cocked, as in baseball's overhand pitching, but when the arm circled around from the 9 o'clock position, almost fully extended back, to the 6 o'clock position, perpendicular with the ground, completing its windmill motion to release the ball. Consequently, the biceps, not the elbow, took the majority of the stress, Verma said.