title: Scapulothoracic muscle activity and recruitment timing in patients with shoulder impingement symptoms and glenohumeral instability.
abstract: BACKGROUND
  Various studies have investigated scapulothoracic muscle activity and recruitment patterns in relation to shoulder complaints in different populations, but a consensus review is lacking.
  
  
  OBJECTIVE
  To systematically review the state of the art regarding scapulothoracic muscle activity and recruitment timing in subjects with shoulder pain compared to pain free controls.
  
  
  METHODS
  Systematic review.
  
  
  METHODS
  The search for relevant articles was performed in Pubmed and Web of Science, including Web of Knowledge, using key words related to shoulder pain, scapulothoracic muscle activity or recruitment timing. Articles were included till November 2012. Case-control studies concerning the scapulothoracic region and muscle recruitment using electromyography (EMG) were included. Articles regarding rotator cuff muscles or neck-shoulder pathologies or studies handling a treatment outcome, were excluded. The methodological quality of the articles was assessed using appropriate risk of bias criteria for case-control studies.
  
  
  RESULTS
  A total of 12 articles were included in the systematic review, containing patients with Shoulder Impingement Syndrome (SIS) or glenohumeral instability. In patients with SIS 3 out of 6 articles showed increased upper trapezius muscle (UT) activity, 3 out of 5 studies showed decreased lower trapezius muscle (LT) activity and 3 out of 5 articles showed decreased serratus anterior muscle (SA) activity. Patients with glenohumeral instability showed contradictory results on scapulothoracic muscle activity patterns. In both SIS and glenohumeral instability patients, no consensus was found on muscle recruitment timing.
  
  
  CONCLUSIONS
  Patients with SIS and glenohumeral instability display numerous variations in scapulothoracic muscle activity compared to healthy controls. In the SIS-group, the LT and SA muscle activity is decreased. In addition, the UT muscle activity is increased among the SIS patients, whereas no clear change is seen among patients with glenohumeral instability. Although the scapulothoracic muscle activity changed, no consensus could be made regarding muscle recruitment timing.
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium; "Pain in Motion" Research Group(1). Electronic address: Filip.struyf@Uantwerpen.be.
authors.forename: Filip
authors.initials: F
authors.lastname: Struyf
authors.affiliation: Rehabilitation Sciences and Physiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cagnie
authors.affiliation: Rehabilitation Sciences and Physiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Ann
authors.initials: A
authors.lastname: Cools
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium; "Pain in Motion" Research Group(1).
authors.forename: Isabel
authors.initials: I
authors.lastname: Baert
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium.
authors.forename: Jolien Van
authors.initials: JV
authors.lastname: Brempt
authors.affiliation: Department of Rehabilitation Medicine, Orbis Medical Centre, Sittard, The Netherlands.
authors.forename: Pieter
authors.initials: P
authors.lastname: Struyf
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Belgium; "Pain in Motion" Research Group(1); Rehabilitation Sciences and Physiotherapy, Ghent University, Ghent, Belgium.
authors.forename: Mira
authors.initials: M
authors.lastname: Meeus
mesh_terms: D004576:Electromyography; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009135:Muscular Diseases / Q000503:physiopathology; D017006:Rotator Cuff; D012782:Shoulder / Q000502:physiology*; D019534:Shoulder Impingement Syndrome / Q000503:physiopathology*; D012785:Shoulder Joint / Q000502:physiology*
keywords: EMG; Glenohumeral instability; Muscle activity; Muscle recruitment timing; Scapula; Shoulder Impingement Syndrome; Shoulder pain