Shoulder Muscle Firing Patterns During the Windmill Softball Pitch

Abstract

The purpose of this study was to describe the activity of eight shoulder muscles during the windmill fast-pitch softball throw. Ten collegiate female pitchers were analyzed with intramuscular electromyography, high-speed cinematography, and motion analysis. The supraspinatus muscle fired maximally during arm elevation from the 6 to 3 o'clock position phase, centralizing the humeral head within the glenoid. The posterior deltoid and teres minor muscles acted maximally from the 3 to 12 o'clock position phase to continue arm elevation and externally rotate the humerus. The pectoralis major muscle accelerated the arm from the 12 o'clock position to ball release phase. The serratus anterior muscle characteristically acted to position the scapula for optimal glenohumeral congruency, and the subscapularis muscle functioned as an internal rotator and to protect the anterior capsule. Although the windmill softball pitch is overtly different from the baseball pitch, several surprising similarities were revealed. The serratus anterior and pectoralis major muscles work in synchrony and seem to have similar functions in both pitches. Although the infraspinatus and teres minor muscles are both posterior cuff muscles, they are characteristically uncoupled during the 6 to 3 o'clock position phase, with the infraspinatus muscle acting more independently below 90 degrees. Subscapularis muscle activity seems important in dynamic anterior glenohumeral stabilization and as an internal rotator in both the baseball and softball throws.

Biomechanics of Windmill Softball Pitching With Implications About Injury Mechanisms at the Shoulder and Elbow

“…The resulting internal rotation velocity was over 4,000°/sec which, although smaller than overhand pitching, is a high magnitude (Table 1). Maffett et a1 (15) observed high levels of activity for the pectoralis major and subscap ularis, contributing to adduction and internal rotation of the humerus during windmill pitching.…”

“…The diagnosis of bicipital tendinitis is often made with little consideration to the possibility of subscapularis or pectoralis strain, which may occur as increased shoulder extension is followed by large forces and torques produced during the delivery motion (Figures 3 and 5). Maffett et al (15) concluded that the high levels of activity for the pectoralis major and subscapularis observed during early delivery also contribute to the stabilization of the anterior capsule of the shoulder. Despite the possibility of injury to these structures, pain in the anterior shoulder is often treated by injection of a steroid/analgesic mixture into the bicipital tendon area.…”

“…In the softball pitcher, forceful deceleration of the upper arm at or just prior to ball release, similar to baseball pitching, places a substantial burden on the posterior rotator cuff muscles (Figures 3 and 5). Maffett et al (15) have shown that, similar to baseball pitching, the teres minor is very active in decelerating the humerus. However, it was concluded that the stress on the teres minor is less during softball pitching because acceleration forces seem to be dissipated through contact of the arm against the lateral thigh.…”

Review of the Windmill Pitch: Biomechanics and Injuries

“…Despite increasing participation in fast-pitch among young women, historically little research has been done on the windmill pitching style. Initially, the consensus was that injury potential was low because the motion appeared seemingly effortless (2)(3)(4)(5)(6). Although recent literature suggests that overuse injuries are prevalent, controversy regarding this matter still exists.…”

“…Existing research has primarily focused on elite pitchers, illustrating that the forces produced with the windmill motion are similar to the overhand throw (3,5). Based on this correlation with the overhand throw, studies of baseball pitchers' delivery were investigated.…”