Changes in passive range of motion and development of glenohumeral internal rotation deficit (GIRD) in the professional pitching shoulder between spring training in two consecutive years

Background: Pitching causes increased mechanical stress to the arm and is thought to result in alterations in range of motion (ROM) as a result of osseous and soft tissue adaptations. Understanding the factors that contribute to alterations in ROM will allow for improved understanding of the pitching shoulder. This study examined humeral torsion (HT) and shoulder mobility over 2 consecutive years.

Methods: Bilateral shoulder mobility and HT were assessed in 33 asymptomatic professional pitchers over 2 spring trainings. A repeated-measures analysis of covariance was used to assess the change in motion of the dominant side/nondominant side across seasons while quantifying pre-existing HT. Prevalence of glenohumeral internal rotation deficit (GIRD) between seasons was compared with χ(2) analysis, and GIRD and non-GIRD pitchers were compared with the independent t test.

Results: The dominant shoulder displayed increased external rotation (11.5° ± 0.1°, P = .02) and decreased internal rotation (-8.4° ± 11.0°, P = .03) and horizontal adduction (-17.6° ± 13.8°, P = .01). The nondominant shoulder remained the same. Mean HT was significantly different (P = .001) in the dominant (10° ± 11°) arm than in the nondominant arm (23° ± 11°). A significant number of pitchers had with GIRD (P < .01) at each assessment.

Conclusions: ROM was significantly altered between seasons of pitching. These changes likely resulted from soft tissue adaptations because we accounted for humeral retrotorsion. Pitchers who developed GIRD displayed a 7° increase in retrotorsion on the dominant shoulder. Changes in the pitching shoulder over time accounting for humeral retrotorsion may suggest pitching ROM is transient and should be monitored.