title: EMG biofeedback effectiveness to alter muscle activity pattern and scapular kinematics in subjects with and without shoulder impingement.
abstract: BACKGROUND
  Muscle imbalance between serratus anterior (SA), upper trapezius (UA), middle trapezius (MT), and lower trapezius (LT) muscles has been observed in subjects with subacromial impingement syndrome (SAIS).
  
  
  OBJECTIVE
  (1) To investigate the effect of electromyography (EMG) biofeedback training on muscle balance ratios and scapular kinematics in healthy adults and subjects with SAIS. (2) To investigate whether the effects of EMG biofeedback on muscle balance ratios are different between groups.
  
  
  METHODS
  Twelve healthy adults and 13 subjects with SAIS were recruited in this study. EMG was used to record the activity of scapular muscles. The ratios (UT/SA, UT/MT, and UT/LT) during exercises with/without EMG biofeedback were calculated. Scapular kinematics were recorded before and after exercises with/without EMG biofeedback.
  
  
  RESULTS
  For the subjects with SAIS, muscle balance ratios were lower during forward flexion with EMG biofeedback than during exercise only (UT/SA: 70.3-45.2; UT/LT: 124.8-94.6). Additionally, similar results were found during side-lying external rotation (UT/MT: 58.5-36.4). For the scapular upward rotation and tipping in both groups, there were no significant differences with and without EMG biofeedback.
  
  
  CONCLUSIONS
  EMG biofeedback improved the scapular muscular balance during training exercises in both groups. Further clinical trials should investigate the long-term effects of EMG biofeedback.
authors.affiliation: School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Han-Yi
authors.initials: HY
authors.lastname: Huang
authors.forename: Jiu-Jenq
authors.initials: JJ
authors.lastname: Lin
authors.forename: Yueliang Leon
authors.initials: YL
authors.lastname: Guo
authors.forename: Wendy Tzyy-Jiuan
authors.initials: WT
authors.lastname: Wang
authors.forename: Yu-Jen
authors.initials: YJ
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D058765:Neurofeedback / Q000379:methods*; D004856:Postural Balance; D012540:Scapula / Q000503:physiopathology*; D019534:Shoulder Impingement Syndrome / Q000175:diagnosis / Q000503:physiopathology* / Q000534:rehabilitation*; D012785:Shoulder Joint / Q000503:physiopathology; D016896:Treatment Outcome; D055815:Young Adult