title: Visual scapular dyskinesis: kinematics and muscle activity alterations in patients with subacromial impingement syndrome.
abstract: OBJECTIVE
  To characterize scapular kinematics and shoulder muscle activity in patients with subacromial impingement syndrome, with and without visually identified scapular dyskinesis.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  Participants with subacromial impingement syndrome (N=38) were visually classified using a scapular dyskinesis test with obvious scapular dyskinesis (n=19) or normal scapular motion (n=19).
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  An electromagnetic motion capture system measured 3-dimensional kinematics of the thorax, humerus, and scapula. Simultaneously, surface electromyography was used to measure muscle activity of the upper, middle, and lower trapezius; serratus anterior; and infraspinatus during ascending and descending phases of weighted shoulder flexion. Separate mixed-model analyses of variance for the ascending and descending phases of shoulder flexion compared kinematics and muscle activity between the 2 groups. Shoulder disability was assessed with the Pennsylvania Shoulder Score (Penn).
  
  
  RESULTS
  The group with obvious dyskinesis reported 6 points lower on Penn shoulder function (0-60 points), exhibited a main group effect of less scapular external rotation of 2.1° during ascent and 2.5° during descent, and had 12.0% higher upper trapezius muscle activity during ascent in the 30° to 60° interval.
  
  
  CONCLUSIONS
  Patients with obvious dyskinesis and subacromial impingement syndrome have reduced scapular external rotation and increased upper trapezius muscle activity, along with a greater loss of shoulder function compared with those without dyskinesis. These biomechanical alterations can lead to or be caused by scapular dyskinesis. Future studies should determine if correction of these deficits will eliminate scapular dyskinesis and improve patient-rated shoulder use.
authors.affiliation: Translational Medicine Program, Department of Medicine, Federal University of Sao Paulo, Sao Paulo, SP, Brazil; Research Support, Center for Clinical Outcomes Studies, A.T. Still University, Mesa, AZ; Department of Physical Therapy, Clinical Biomechanics, Orthopedic and Sports Outcomes Research Laboratory, Virginia Commonwealth University, Richmond, VA. Electronic address: alopes@atsu.edu.
authors.forename: Andrea Diniz
authors.initials: AD
authors.lastname: Lopes
authors.affiliation: School of Kinesiology, Marshall University, Huntington, WV.
authors.forename: Mark K
authors.initials: MK
authors.lastname: Timmons
authors.affiliation: Department of Physical Therapy, Clinical Biomechanics, Orthopedic and Sports Outcomes Research Laboratory, Virginia Commonwealth University, Richmond, VA.
authors.forename: Molly
authors.initials: M
authors.lastname: Grover
authors.affiliation: Translational Medicine Program, Department of Medicine, Federal University of Sao Paulo, Sao Paulo, SP, Brazil.
authors.forename: Rozana Mesquita
authors.initials: RM
authors.lastname: Ciconelli
authors.affiliation: Department of Physical Therapy, Clinical Biomechanics, Orthopedic and Sports Outcomes Research Laboratory, Virginia Commonwealth University, Richmond, VA; Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA. Electronic address: lmichene@usc.edu.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Michener
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D020820:Dyskinesias / Q000209:etiology / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D006811:Humerus / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D017006:Rotator Cuff / Q000503:physiopathology; D012540:Scapula / Q000503:physiopathology*; D019534:Shoulder Impingement Syndrome / Q000150:complications / Q000503:physiopathology*; D012785:Shoulder Joint / Q000503:physiopathology*; D064171:Superficial Back Muscles / Q000503:physiopathology; D013909:Thorax / Q000503:physiopathology
keywords: Electromyography; Rehabilitation; Scapula; Shoulder impingement syndrome