title: Effects of muscle fatigue on 3-dimensional scapular kinematics.
abstract: OBJECTIVE
  To determine the effects of fatigue during an external rotation task on 3-dimensional scapular kinematics.
  
  
  METHODS
  A single-group, pretest-posttest measurement design.
  
  
  METHODS
  Research laboratory.
  
  
  METHODS
  Thirty healthy subjects.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Three-dimensional scapular kinematics were recorded with a Polhemus magnetic tracking device during arm elevation in the scapular plane.
  
  
  RESULTS
  There was a significant fatigue effect for all scapular rotations in the early to middle phases of humeral elevation. Significantly less posterior tilting (up to 90 degrees of elevation), external rotation (up to 120 degrees of elevation), and upward rotation (up to 60 degrees of elevation) were observed. Additionally, there were fair to good correlations (r range,.39-.60) between the changes in scapular posterior tilting and the amount of muscle fatigue.
  
  
  CONCLUSIONS
  Fatigue in shoulder external rotation altered the scapular resting position and the movement of posterior tilting in the early range during arm elevation in the scapular plane. Observed changes in scapular kinematics may affect the amount of area in the subacromial space and facilitate impingement. Data regarding changes produced by fatigue of the external rotators may also help with the development of a model of diminished rotator cuff function.
authors.affiliation: Department of Rehabilitation Sciences, Biomechanics Laboratory, Drexel University, Philadelphia, PA 97403, USA.
authors.forename: Nian-Tuen
authors.initials: NT
authors.lastname: Tsai
authors.forename: Phil W
authors.initials: PW
authors.lastname: McClure
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Karduna
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology / Q000503:physiopathology; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008280:Magnetics; D008297:Male; D008954:Models, Biological; D018763:Muscle Fatigue / Q000502:physiology*; D010865:Pilot Projects; D016059:Range of Motion, Articular; D012146:Rest; D012399:Rotation; D017006:Rotator Cuff / Q000502:physiology* / Q000503:physiopathology; D012540:Scapula / Q000502:physiology* / Q000503:physiopathology; D012785:Shoulder Joint / Q000502:physiology / Q000503:physiopathology; D019415:Torque