Relationship Between Glenohumeral Internal Rotation Deficit and Medial Elbow Torque in High School Baseball Pitchers

Abstract

Background: Alterations in throwing mechanics have been identified as a risk factor for overuse injuries in baseball players. Glenohumeral internal rotation deficit (GIRD) has been found to adversely affect throwing mechanics, but the effect of GIRD on medial elbow torque is unclear.

Purpose: To investigate the relationship between GIRD and medial elbow torque in high school-aged baseball pitchers.

Study design: Descriptive laboratory study.

Methods: High school baseball pitchers (14-18 years old) were recruited for participation in this study. Players' height, weight, body mass index, and arm measurements were recorded as well as shoulder and elbow range of motion measurements. GIRD was calculated from the difference between dominant and nondominant shoulder internal rotation. Participants then pitched 5 fastballs at maximum effort while wearing a wireless sensor that recorded elbow torque, arm slot, arm speed, shoulder rotation, and ball velocity. Principal component analysis was performed to determine which variables were associated with elbow torque or ball velocity.

Results: Twenty-three high school pitchers participated in this study; 35% (n = 8) of participants exhibited GIRD of at least 20°. The mean GIRD was 15.3°± 11.2° and was not a predictor of medial elbow torque (P = .205) or ball velocity (P = .333). Ball velocity, age, and height were predictors of medial elbow torque (P = .012, P = .003, and P = .024, respectively).

Conclusion: In high school baseball pitchers, GIRD was not associated with medial elbow torque during the pitching motion. Instead, ball velocity, player age, and player height carried greater significance.

Clinical relevance: This study suggests that high school pitchers with GIRD do not have an inherently greater risk for increased medial elbow torque during the throwing motion. It is recommended that pitchers instead assess their ball velocity to evaluate for relative differences in medial elbow torque.

Keywords: GIRD; Motus; UCL injury; baseball; elbow stress; elbow torque; pitchers.