title: Importance of contraction history on muscle force of porcine urinary bladder smooth muscle.
abstract: BACKGROUND
  The purpose of this study was to provide a comprehensive dataset of porcine urinary bladder smooth muscle properties. Particularly, the history dependence of force production, namely force depression (FD) following shortening and force enhancement (FE) following stretch, was analysed. During active micturition, the circumference of the urinary bladder changes enormously. Thus, FD might be an important phenomenon during smooth muscle contraction.
  
  
  METHODS
  Electrically stimulated, intact urinary bladder strips from pigs (n = 10) were suspended in an aerated-filled organ bath, and different isometric, isotonic, and isokinetic contraction protocols were performed to determine the force-length and the force-velocity relation. FD and FE were assessed in concentric and eccentric contractions with different ramp lengths and ramp velocities.
  
  
  RESULTS
  Bladder smooth muscles exhibit considerable amounts of FD and FE. The amount of FD increased significantly with ramp length, while FE did not change. However, FE and FD were independent of ramp velocity.
  
  
  CONCLUSIONS
  The results imply that smooth muscle bladder strips exhibit similar muscle properties and history-dependent behaviour compared to striated muscles. The provided dataset of muscle properties is important for bladder modelling as well as for the analyses and interpretation of dynamic bladder filling and voiding.
authors.affiliation: Institute of Sport- and Movement Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Baden-Württemberg, Germany. robin.menzel@inspo.uni-stuttgart.de.
authors.forename: Robin
authors.initials: R
authors.lastname: Menzel
authors.affiliation: Institute of Solid Mechanics, Technische Universität Braunschweig, 38106, Braunschweig, Niedersachsen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Böl
authors.affiliation: Institute of Sport- and Movement Science, University of Stuttgart, Allmandring 28, 70569, Stuttgart, Baden-Württemberg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Siebert
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004558:Electric Stimulation / Q000379:methods; D023421:Models, Animal; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000502:physiology*; D013552:Swine; D001743:Urinary Bladder / Q000473:pathology / Q000502:physiology*; D014554:Urination / Q000502:physiology*
keywords: Force depression; Force enhancement; Force–length relation; Force–velocity relation; Muscle properties; Pig