GIRD and Medial Elbow Torque in High School Pitchers

Smith DG, Swantek AJ, Gulledge CM, et al. Relationship between glenohumeral internal rotation deficit and medial elbow torque in high school baseball pitchers. Am J Sports Med. 2019;47(12):2821-2826. doi:10.1177/0363546519868939

Background

In baseball players, glenohumeral internal rotation deficit (GIRD) has been defined as a 20° difference in passive internal rotation between the dominant and nondominant shoulders.  There is conflicting evidence about an association between GIRD and upper extremity injury in baseball players.  A recent meta-analysis showed no significant relationship between GIRD and upper extremity injury in a pooled sample of 2,195 overhead athletes1.  No studies have specifically looked at the relationship between GIRD and medial elbow torque in youth baseball pitchers.

Purpose

The purpose of this study was to investigate the association of GIRD with medial elbow torque in adolescent pitchers. The secondary purpose of the study was to determine if the GIRD was related to other measures of throwing kinematics.

Study Population

  • A sample of 23 male high school baseball players (14-18 years old).
  • Pitchers were not injured and were actively throwing.
  • Exclusion criteria included any pitcher with complaints of arm soreness or those who threw “sidearm”.

Research Methods

Shoulder range of motion (ROM) was measured in the supine position before any throwing.  Internal and external rotation was measured in 90° of abduction with the scapula stabilized at the acromion by a second examiner.   The Motus Global sleeve was fitted with the sensor placed approximately 1.5 inches distal to the medial epicondyle of the humerus.  Players were instructed to warm up with their preferred routine. The pitching protocol consisted of 5 fastball pitches, thrown at maximum effort.  All pitches were thrown from a mound to a catcher at 60 ft and 6 inches. Ball velocity was recorded using a radar gun.  Variables collected and analyzed were ball velocity, elbow torque, arm slot, arm speed, and shoulder rotation ROM.

Key Results

  • GIRD (defined as a 20° difference between sides) was measured in 35% (n = 8) of participants.
  • The mean ball velocity was 67.5 mph, and the mean elbow torque was 52.3 Nm.
  • The inter-rater reliability for the examiners was moderate with an ICC of 0.55 (P = .003).
  • No significant correlations between GIRD and ball velocity.
  • No significant correlations between GIRD and medial elbow torque.
  • Medial elbow torque significantly increased with ball velocity (r = 0.0467), age (r = 0.549), and height (r = 0417).
  • There was a strong positive correlation between ball velocity and age (P < 0.001), ball velocity and height (P = .001); and ball velocity and weight (P = .003).
  • There was no significant correlation between total ROM deficit and elbow torque, arm slot, arm speed, or shoulder rotation (P > 0.05).

Study Limitations 

  • A small sample size of 23 pitchers
  • No cause-and-effect relationship can be established based on study design
  • Results may not be generalizable to college or professional pitchers

Final Thoughts and Practical Implications

This study showed no association between GIRD and medial elbow torque in a small sample of high school baseball pitchers.  Also, GIRD did not show any correlation with ball velocity.  Medial elbow torque increased with increasing age, height, and weight of the pitcher.  These same variables were positively correlated with ball velocity.  This highlights the association of ball velocity as a key factor related to medial elbow torque and potentially ulnar collateral ligament injury.

During the pitching motion, the lower limbs and trunk are the main force generators.   As the forces successively transfer from the lower body to the upper the load is reduced at each joint.  Optimizing force generation and transfer in the lower body and trunk will minimize stress at the pitcher’s shoulder and elbow.  It is plausible that minimizing medial elbow torque during pitching is best achieved by optimizing lower body and trunk function.  Impairments at the shoulder and elbow, such as GIRD, may be less relevant.

Posterior shoulder tightness and GIRD is common immediately following a throwing session.  GIRD may also develop over the course of a long competitive season.  Therefore, addressing impairments in GIRD as part of a pitcher’s recovery program has face validity.  However, interventions aimed at correcting GIRD may not be a necessary component of elbow injury prevention programs.   It may be more beneficial to include interventions targeting the trunk and lower body in these types of programs.  Further research would be needed to support this hypothesis.

References

  1. Keller RA, De Giacomo AF, Neumann JA, Limpisvasti O, Tibone JE. Glenohumeral internal rotation deficit and risk of upper extremity injury in overhead athletes: A meta-analysis and systematic review. Sport Heal A Multidiscip Approach. 2018; Online:1-8. doi:10.1177/1941738118756577

 

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