title: Alternative methods for measuring scapular muscles protraction and retraction maximal isometric forces.
abstract: BACKGROUND
  The importance of the scapular stabilizing muscles has led to an increased interest in quantitative measurements of their strength. Few studies have measured isometric or concentric isokinetic forces. Additionally, limited reports exist on the reliability of objective measures for testing scapular protraction and retraction muscle strength or scapular testing that does not involve the glenohumeral joint.
  
  
  OBJECTIVE
  To determine the reliability of four new methods of measuring the maximal isometric strength of key scapular stabilizing muscles for the actions of protraction and retraction, both with and without the involvement of the glenohumeral (GH) joint.
  
  
  METHODS
  The Isobex® stationary tension dynamometer was used to measure the maximal isometric force (kg) on thirty healthy females (ages 22-26 years). Three measures were taken for each method that was sequentially randomized for three separate testing sessions on three nonconsecutive days.
  
  
  RESULTS
  Intraclass correlations (ICC2,3) for intrasession reliability and (ICC3,3) for intersession reliability ranged from 0.95 to 0.98, and 0.94 to 0.96 respectively. The standard errors of measurement (95% confidence interval [CI]) were narrow. Scatter grams for both protraction and retraction testing methods demonstrated a significant relationship, 0.92 for protraction (95% CI 0.83 to 0.96) and 0.93 for retraction (95% CI 0.87 to 0.97). Bland-Altman plots indicated good agreement between the two methods for measuring protraction strength but a weaker agreement for the two methods measuring retraction strength.
  
  
  CONCLUSIONS
  The four new methods assessed in this study indicate reliable options for measuring scapular protraction or retraction isometric strength with or without involving the GH joint for young healthy females.
authors.forename: Duane A
authors.initials: DA
authors.lastname: Williams
authors.forename: James R
authors.initials: JR
authors.lastname: Roush
authors.forename: George J
authors.initials: GJ
authors.lastname: Davies
authors.forename: Todd S
authors.initials: TS
authors.lastname: Ellenbecker
authors.forename: Mitchell J
authors.initials: MJ
authors.lastname: Rauh