title: Glenohumeral rotational range of motion in collegiate overhead-throwing athletes during an athletic season.
abstract: BACKGROUND
  Repetitive throwing at high velocities leads to altered range of motion (ROM) in the dominant shoulder compared with the nondominant shoulder in overhead-throwing athletes. Loss of glenohumeral internal rotation (IR), or glenohumeral internal-rotation deficit (GIRD), is associated with shoulder injuries. Therefore, GIRD should be evaluated during the clinical examination of the thrower's shoulder.
  
  
  OBJECTIVE
  To assess glenohumeral ROM in competitive baseball and softball athletes at 3 intervals over the course of an athletic season in order to (1) examine changes in ROM over time and (2) monitor the prevalence of GIRD.
  
  
  METHODS
  Observational, repeated-measures study.
  
  
  METHODS
  Collegiate athletic training room.
  
  
  METHODS
  Forty-eight healthy National Collegiate Athletic Association (NCAA) Division I or Division II athletes (age = 19 + or - 1 years, height = 174 + or - 14 cm, mass = 77.8 + or - 18.1 kg; 19 softball, 29 baseball players).
  
  
  METHODS
  We measured glenohumeral IR, external rotation (ER), total arc (ER + IR), and GIRD at 3 times: prefall, prespring, and postspring. We calculated GIRD in 2 ways: as the difference in IR between dominant and nondominant shoulders and as the percentage of the total arc.
  
  
  RESULTS
  In the dominant shoulder, ER increased during the season (F(2,96) = 17.433, P < .001), but IR remained the same (F(2,96) = 1.839, P = .17). The total arc in the dominant shoulder increased between time intervals (F(2,96) = 14.030, P < .001); the mean difference between prefall and postspring measurements was 9.694 degrees (P < .001), and the mean difference between prefall and postspring measurements was 10.990 degrees (P < .001). In the nondominant shoulder, ER increased over the season (F(2,96) = 23.395, P < .001), but IR did not change over the season (F(2,96) = 0.087, P = .90). The total arc in the nondominant shoulder increased between prefall and prespring measurements and between prefall and postspring measurements (F(2,96) = 18.552, P < .001). No changes were noted in GIRD over time. However, more athletes with GIRD were identified with the GIRD (IR difference) calculation in prefall (n = 6) than in prespring (n = 1) and postspring (n = 4) (Cochran Q = 5.2, P = .07). In addition, more athletes with GIRD were identified with the GIRD (% total arc) calculation in postspring (n = 6) than in prefall (n = 5) or prespring (n = 4) (Cochran Q = 2.6, P = .27).
  
  
  CONCLUSIONS
  Healthy NCAA Division I and Division II athletes did not display changes in glenohumeral IR over an athletic season. However, they gained in ER and total arc during the season in both shoulders. Future researchers should investigate changes over multiple seasons. The 2 methods of calculating GIRD identified different athletes as having GIRD, indicating that additional investigation is warranted to determine the clinical benefits of each method.
authors.affiliation: University of Arkansas, 1-University, HPER 308, Fayetteville, AR 72701, USA. pdwelly@gmail.com
authors.forename: Priscilla M
authors.initials: PM
authors.lastname: Dwelly
authors.forename: Brady L
authors.initials: BL
authors.lastname: Tripp
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Tripp
authors.forename: Lindsey E
authors.initials: LE
authors.lastname: Eberman
authors.forename: Steven
authors.initials: S
authors.lastname: Gorin
mesh_terms: D001265:Athletic Injuries / Q000453:epidemiology / Q000209:etiology; D001484:Baseball / Q000293:injuries / Q000502:physiology*; D001696:Biomechanical Phenomena; D012090:Cumulative Trauma Disorders / Q000453:epidemiology / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012399:Rotation; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000502:physiology*; D014481:United States / Q000453:epidemiology; D014495:Universities; D055815:Young Adult