title: Changes in humeral torsion and shoulder rotation range of motion in high school baseball players over a 1-year period.
abstract: BACKGROUND
  The torsional stress on a baseball player's throwing limb has been theorized to affect humeral retrotosion during skeletal maturity. This study investigated 1) changes in humeral retrotorsion and shoulder rotation range of motion over a 1-year period in high school baseball players, and 2) relationship between a 1-year change in dominant limb retrotorsion and the number of seasons participants played on organized baseball teams.
  
  
  METHODS
  Humeral retrotorsion and shoulder range of motion were measured a year apart in a total of 138 high school baseball players. Baseball participation history over the year was captured using a questionnaire. Changes in bilateral humeral retrotorsion and range of motion over a year and effects of baseball participation on changes in humeral retrotorsion and range of motion were assessed using analysis of variance models.
  
  
  RESULTS
  Humeral retrotorsion did not significantly change over the year regardless of the number of seasons participants played baseball (P>0.05). The participants' dominant limb internal rotation range of motion decreased slightly over a year (2.0°, P=0.015), while external rotation (7.8°, P<0.01) and total rotation (11.9°, P<0.01) range of motion decreased bilaterally among the participants who only played baseball in 1 season.
  
  
  CONCLUSIONS
  Adaptation in humeral retrotorsion seems to occur prior to high school age. Our observations suggest that change in shoulder range of motion in high school baseball players are attributed to soft tissue contracture. This provides a support that stretching exercises should be implemented when significant changes in range of motion are identified in high school baseball players.
authors: Department of Health and Kinesiology, University of Texas at San Antonio, San Antonio, TX, San Antonio, TX, USA. Sakiko.Oyama@utsa.edu
authors: Sakiko
authors: S
authors: Oyama
authors: Elizabeth E
authors: EE
authors: Hibberd
authors: Joseph B
authors: JB
authors: Myers
mesh_terms: D000293:Adolescent; D001484:Baseball / Q000502:physiology*; D015331:Cohort Studies; D006801:Humans; D006811:Humerus / Q000502:physiology*; D008137:Longitudinal Studies; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D012782:Shoulder / Q000502:physiology*