Biomechanics Related to Increased Softball Pitcher Shoulder Stress: Implications for Injury Prevention

Am J Sports Med. 2022 Jan;50(1):216-223. doi: 10.1177/03635465211055141. Epub 2021 Nov 15.

Abstract

Background: Softball pitchers exhibit high throwing shoulder distraction force, which is a theorized mechanism of throwing shoulder overuse injury. Windmill pitching involves a variety of highly individualistic pitching styles, and certain kinematics preceding ball release likely influence the amount of shoulder stress that a pitcher accrues.

Purpose: To examine the association of trunk and throwing arm kinematics, kinetics, and timing variables with peak throwing shoulder distraction force in high school softball pitchers.

Study design: Descriptive laboratory study.

Methods: A total of 37 high school pitchers (mean ± SD; height, 1.71 ± 0.06 m; weight, 75.53 ± 16.12 kg; age, 16 ± 2 years) threw 10 fastball pitches at regulation distance (43 ft [13.1 m]) and with maximum effort. Kinematic data were collected at 240 Hz using an electromagnetic motion capture system synced with motion analysis software. The 3 fastest pitches were averaged and analyzed. Kinematic, kinetic, and timing variables were entered into a stepwise linear regression analysis.

Results: Four variables were included in the significant model (F4,39 = 147.51; P < .001) and explained peak shoulder distraction force (R2 = 0.944; adjusted R2 = 0.938; SE = 0.036): increased peak elbow distraction force (t = 19.90; P < .001) and extension moment (t = 3.63; P = .001), as well as decreased elbow flexion velocity (t = -2.37; P = .023) and trunk flexion at foot contact of the pitch (t = -3.00; P = .005).

Conclusion: Elbow kinetics and angular velocity, as well as trunk positioning at foot contact, are associated with peak throwing shoulder distraction force in high school softball pitchers.

Clinical relevance: Variables associated with peak throwing shoulder distraction force provide information regarding injury mechanism and coachable cues that might reduce shoulder injury risk among pitchers.

Keywords: biceps stress; shoulder distraction force; shoulder injury mechanism; softball pitching; sports medicine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Baseball*
  • Biomechanical Phenomena
  • Elbow
  • Elbow Joint*
  • Humans
  • Shoulder Joint*