title: Contribution of pelvic floor muscles to stiffness of the pelvic ring.
abstract: METHODS
  A biomechanical study in embalmed specimens, on the relation between applied tension in the pelvic floor muscles, stiffness of the pelvic ring and generation of movement in the sacroiliac joints.
  
  
  OBJECTIVE
  To gain insight into the effect of tension in the pelvic floor muscles on stiffness of the pelvic ring. Background. According to a model on selfbracing pelvic floor muscles have the capacity to stiffen the sacroiliac joints. However, this capacity has not been demonstrated in vitro yet.
  
  
  METHODS
  In 18 embalmed specimens an incremental moment was applied to the sacroiliac joints to induce rotation of the innominate bones in the sagittal plane. After assessment of the relationship between rotation angle and moment, springs were applied to the pelvis to simulate tension in the pelvic floor muscles. During the simulated tension the measurements were repeated. Differences in stiffness before and after applying springs were tested for significance.
  
  
  RESULTS
  In females, simulated tension in the pelvic floor muscles stiffened the sacroiliac joints with 8.5% (P < 0.05). In males no significant changes occurred. In both sexes a backward rotation of the sacrum occurred due to simulated tension in the pelvic floor muscles (P < 0.05). The sacroiliac joints of female specimens were more mobile in comparison to male specimens (P < 0.05).
  
  
  CONCLUSIONS
  In females, pelvic floor muscles have the capacity to increase stiffness of the pelvic ring. In addition, these muscles can generate a backward rotation of the sacrum in both sexes.
  
  
  CONCLUSIONS
  The ability of pelvic floor muscles to increase stiffness of the pelvic ring is of importance in patients with impairment of pelvic stability, especially in pelvic pain patients. Increased activity of these pelvic floor muscles might compensate for loss of pelvic stability by stiffening the pelvic ring and restoring proper load transfer through the lumbopelvic region.
authors.affiliation: Department of Biomedical Physics and Technology, Faculty of Medicine and Allied Health Sciences, Erasmus Medical Center, Postbus 1738, 3000 DR Rotterdam, The Netherlands. a.goudzwaard@erasmusmc.nl
authors.forename: Annelies
authors.initials: A
authors.lastname: Pool-Goudzwaard
authors.forename: Gilbert Hoek
authors.initials: GH
authors.lastname: van Dijke
authors.forename: Marcel
authors.initials: M
authors.lastname: van Gurp
authors.forename: Paul
authors.initials: P
authors.lastname: Mulder
authors.forename: Chris
authors.initials: C
authors.lastname: Snijders
authors.forename: Rob
authors.initials: R
authors.lastname: Stoeckart
mesh_terms: D000368:Aged; D002102:Cadaver; D004548:Elasticity; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D010384:Pelvic Bones / Q000502:physiology*; D017773:Pelvic Floor / Q000502:physiology; D010812:Physical Stimulation / Q000379:methods; D004856:Postural Balance / Q000502:physiology*; D012446:Sacroiliac Joint / Q000502:physiology*; D012737:Sex Factors; D013314:Stress, Mechanical; D019415:Torque