title: Electromyographic analysis: shoulder muscle activity revisited.
abstract: BACKGROUND
  Restoring optimal strength and biomechanics of a pathologic shoulder knowledge of activity patterns of healthy glenohumeral muscles is mandatory. Yet, data on normal shoulder muscle activity are not always conclusive. The study was undertaken (a) to evaluate muscle activity patterns in the healthy shoulder using surface and fine-wire electromyography (EMG), and (b) to assess method's suitability in the clinical setting especially regarding painfulness and practicability.
  
  
  METHODS
  Surface and fine-wire EMG was performed on 11 healthy subjects (2f/9 m, Ø age 28 years) to assess 14 muscles including rotator cuff muscles during 8 planar standardised shoulder movements (abduction, forward flexion, internal and external rotation in neutral, 45° and 90° abduction). Pain was assessed using the visual analogue scale before testing, after inserting the fine-wire electrodes, after maximal voluntary contraction, before and after exercises, and after electrode removal.
  
  
  RESULTS
  The most important finding regarding EMG activity patterns in the healthy shoulder was that the subscapularis activity was found to play a major role in abduction and forward flexion. Furthermore, this study was able to show that EMG measurements, especially fine-wire EMG, is prone to high failure rates (up to 32%); however, pain was not a limiting factor.
  
  
  CONCLUSIONS
  The present study (1) revealed a new insight, especially finding the subscapularis activity playing a major role in abduction and forward flexion of the healthy shoulder; and (2) motion analysis system and the use of fine-wire electrodes were prone to failure; however, pain was not a limiting factor.
  
  
  METHODS
  Basic Science, Electrodiagnostic Study.
authors.affiliation: Department of Orthopaedics, St. Vincent Hospital Vienna, Stumpergasse 13, 1060, Vienna, Austria, philipp.heuberer@bhs.at.
authors.forename: Philipp
authors.initials: P
authors.lastname: Heuberer
authors.forename: Andreas
authors.initials: A
authors.lastname: Kranzl
authors.forename: Brenda
authors.initials: B
authors.lastname: Laky
authors.forename: Werner
authors.initials: W
authors.lastname: Anderl
authors.forename: Christian
authors.initials: C
authors.lastname: Wurnig
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D017006:Rotator Cuff / Q000502:physiology*; D012782:Shoulder / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology; D055815:Young Adult