title: The effect of cyclic loading simulating oscillatory joint mobilization on the posterior capsule of the glenohumeral joint: a cadaveric study.
abstract: METHODS
  Experimental laboratory design.
  
  
  OBJECTIVE
  To examine the effect of force and repetition during oscillatory joint mobilizations on the posterior capsule of the glenohumeral joint.
  
  
  BACKGROUND
  The optimal external force and frequency to be used during joint mobilization to elongate the posterior capsule of the glenohumeral joint has yet to be identified.
  
  
  METHODS
  Twenty-one posterior capsules were harvested from fresh-frozen shoulders. A cyclic loading test simulating oscillatory posterior joint mobilization on the shoulder specimens was performed with a material testing machine. The specimens were assigned to 3 different loading groups simulating joint mobilization in the toe (5 N), transition (20 N), and beginning of the linear regions (40 N) of the load displacement curve. Displacement of the humeral head at an applied load of 5 N was recorded at the 1st, 100th, 200th, 300th, 400th, 500th, and 600th cycles and at 1 hour after completion of the cyclic loading. Furthermore, stiffness was calculated after the 1st and 600th cycles and 1 hour after testing.
  
  
  RESULTS
  Humeral head displacement was significantly greater for the 100th to 600th cycle, compared to the 1st cycle, for all 3 loading groups. Significant increases in displacement and stiffness were observed between the 1st cycle and 1 hour after completion of the cyclic tests for both the 20-N and 40-N loading groups.
  
  
  CONCLUSIONS
  While oscillatory joint mobilization to a force of 5 N resulted in temporary elongation of the posterior capsule, mobilization to loads of 20 and 40 N resulted in sustained elongation of the capsule for up to 1 hour. Our findings also suggest that mobilization up to loads that represent the beginning of the linear region of the load displacement curve could be performed without serious damage to the posterior capsule.
authors.affiliation: Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic College of Medicine, 200 First Street, SW, Rochester, MN 55905, USA.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Muraki
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamamoto
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: Berglund
authors.forename: John W
authors.initials: JW
authors.lastname: Sperling
authors.forename: Scott P
authors.initials: SP
authors.lastname: Steinmann
authors.forename: Robert H
authors.initials: RH
authors.lastname: Cofield
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
mesh_terms: D002102:Cadaver; D006801:Humans; D017746:Joint Capsule / Q000502:physiology*; D009038:Motion; D016059:Range of Motion, Articular / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*