Single-Leg Squat and Upper Extremity Kinetics during Windmill Softball Pitching

The high volume of pitches in softball generates substantial shoulder forces, making it a common injury site. Effective proximal-to-distal energy transfer through the lower extremities and lumbopelvic-hip complex is critical for force distribution, although this relationship has not been well examined in youth. The purpose of this study was to assess the relationship between single-leg squat compensatory mechanics and upper extremity kinetics in youth softball pitchers. A total of 72 youth softball pitchers participated. Participants performed isometric hip strength testing, bilateral single-leg squats, and pitched 3-10 fastballs. Separate ordinary least squares regression models were conducted for each pitch kinetic variable, with all single-leg squat variables entered together as predictors for each separate pitch kinetic dependent variable. Drive knee valgus and hip strength ratio, along with pitch velocity, were associated with relative peak shoulder distraction force, while stride trunk lean and age were associated with relative peak EDF. Drive trunk rotation was the only variable associated with shoulder resultant force and shoulder extension torque, and no variables were associated with shoulder or elbow flexion torque. The current findings support the concept that proximal trunk control and lower extremity stability during single-leg tasks may be related to distal joint loading during the pitching motion in softball.