title: The initial effects of a sustained glenohumeral postero-lateral glide during elevation on shoulder muscle activity: A repeated measures study on asymptomatic shoulders.
abstract: BACKGROUND
  Manual therapy enhances pain-free range of motion and reduces pain levels, but its effect on shoulder muscle activity is unclear. This study aimed to assess the effects of a sustained glenohumeral postero-lateral glide during elevation on shoulder muscle activity.
  
  
  METHODS
  Thirty asymptomatic individuals participated in a repeated measures study of the electromyographic activity of the supraspinatus, infraspinatus, posterior deltoid, and middle deltoid. Participants performed four sets of 10 repetitions of shoulder scaption and abduction with and without a glide of the glenohumeral joint. Repeated-measures multivariate analysis of variance (MANOVA) was used to assess the effects of movement direction (scaption and abduction), and condition (with and without glide) (within-subject factors) on activity level of each muscle (dependent variables). Significant MANOVAs were followed-up with repeated-measures one-way analysis of variance.
  
  
  RESULTS
  During shoulder scaption with glide, the supraspinatus showed a reduction of 4.1% maximal isometric voluntary contraction (MVIC) (95% CI 2.4, 5.8); and infraspinatus 1.3% MVIC (95% CI 0.5, 2.1). During shoulder abduction with a glide, supraspinatus presented a reduction of 2.5% MVIC (95% CI 1.1, 4.0), infraspinatus 2.1% MVIC (95% CI 1.0, 3.2), middle deltoid 2.2% MVIC (95% CI = 0.4, 4.1), posterior deltoid 2.1% MVIC (95% CI 1.3, 2.8).
  
  
  CONCLUSIONS
  In asymptomatic individuals, sustained glide reduced shoulder muscle activity compared to control conditions. This might be useful in enhancing shoulder movement in clinical populations. Reductions in muscle activity might result from altered joint mechanics, including simply helping to lift the arm, and/or through changing afferent sensory input about the shoulder.
authors.affiliation: Centre for Health, Activity and Rehabilitation Research, School of Physiotherapy, University of Otago, New Zealand. Electronic address: Daniel.ribeiro@otago.ac.nz.
authors.forename: Daniel Cury
authors.initials: DC
authors.lastname: Ribeiro
authors.affiliation: School of Physical Education, University of Otago, New Zealand.
authors.forename: Marcelo Peduzzi
authors.initials: MP
authors.lastname: de Castro
authors.affiliation: Centre for Health, Activity and Rehabilitation Research, School of Physiotherapy, University of Otago, New Zealand.
authors.forename: Gisela
authors.initials: G
authors.lastname: Sole
authors.affiliation: School of Health and Rehab Sciences, The University of Queensland, Australia.
authors.forename: Bill
authors.initials: B
authors.lastname: Vicenzino
mesh_terms: D000328:Adult; D004576:Electromyography; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D012782:Shoulder / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D055815:Young Adult
keywords: Electromyography; Manual therapies; Musculoskeletal; Shoulder