Pitcher’s Leg Motion Alters Elbow Force

Drive-leg kinematics during the windup and push off may affect the intensity of the forces on the pitcher’s throwing elbow, a new study finds.

In the study, “Drive-Leg Kinematics During the Windup and Push off Is Associated With Pitching Kinetics at Later Phases of the Pitch,” which was published on March 3, 2022 in The American Journal of Sports Medicine, the researchers analyzed the relationship between drive-leg knee valgus angle during the windup and subsequent pitching mechanics.

“Inconsistent findings exist between drive-leg ground-reaction forces and pitching mechanics. Previous literature has largely reported drive-leg mechanics and ground-reaction forces at the start of the push off phase for their role in initiating force development. Little research has assessed drive-leg kinematics that includes a pitcher’s windup motion to determine its effects on subsequent phases in the pitching motion,” the researchers wrote.

“We hypothesized that the drive-leg knee valgus angle during the early portion of the pitching motion would alter later phases’ pitching mechanics. A secondary aim was to assess ground-reaction forces to determine if the drive-leg knee valgus angle was associated with changes in force. We hypothesized that an increased drive-leg knee valgus angle would increase ground-reaction forces during the pitching motion.”

The study included 17 high school baseball pitchers (mean age, 16.1 ± 0.9 years; mean height, 180.0 ± 4.8 cm; mean weight, 75.5 ± 7.5 kg). The researchers collected kinematic data and ground-reaction forces using an electromagnetic tracking system and force plates. The pitchers were asked to throw maximal-effort fastballs during the windup and push off phases of the pitch.

The data showed a strong relationship between drive-leg knee valgus angle during the windup (Fchange 1,12) = 16.13; P = .002; R² = 0.695) and lateral ground-reaction forces in the arm-cocking phase. The researchers also found a significant relationship between drive-leg knee valgus angle during push off (Fchange 2,11) = 10.21; P = .003; R² = 0.716) and lateral ground-reaction forces in the arm-cocking phase and pitching-elbow valgus moment in the acceleration phase.

“Drive-leg knee valgus angle during the windup and push off had a significant relationship with drive-leg ground-reaction forces and pitching-elbow valgus moment at later stages of the pitching cycle,” the researchers wrote.

“Assessments of drive-leg kinematics during the windup and push off may be useful in identifying inefficient movement patterns that can have an effect on the direction of a pitcher’s drive-leg force contribution, which can lead to increased forces on the throwing elbow.”

Study authors include Anthony Favia, M.A. Jessica L. Downs Talmage, Ph.D., and Gretchen D. Oliver, Ph.D. all of Auburn University in Alabama. Hillary A. Plummer, Ph.D. of the United States Army Aeromedical Research Laboratory at Fort Rucker in Alabama and the Oak Ridge Institute for Science and Education in Tennessee also contributed to the study.