title: Skeletal muscle contraction. The thorough definition of the contractile event requires both load acceleration and load mass to be known.
abstract: BACKGROUND
  The scope of this work is to show that the correct and complete definition of the system of muscle contraction requires the knowledge of both the mass and the acceleration of the load.
  
  
  RESULTS
  The aim is achieved by making use of a model of muscle contraction that operates into two phases. The first phase considers the effects of the power stroke in the absence of any hindrance. In the second phase viscous hindrance is introduced to match the experimental speed and yield of the contraction. It is shown that, at constant force of the load, changing load acceleration changes the time course of the pre-steady state of myofibril contraction. The decrease of the acceleration of the load from 9.8 m.s(-2) to 1 m.s(-2) increases the time length of the pre-steady state of the contraction from a few microseconds to many hundreds of microseconds and decreases the stiffness of the active fibre.
  
  
  CONCLUSIONS
  We urge that in the study of muscle contraction both the mass and the acceleration of the load are specified.
authors.affiliation: Dipartimento di Biochimica e Biologia Molecolare, Università di Ferrara, Via Borsari 46, 44100, Ferrara, Italy. enrico.grazi@unife.it
authors.forename: Enrico
authors.initials: E
authors.lastname: Grazi
authors.forename: Sara
authors.initials: S
authors.lastname: Pozzati
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D007700:Kinetics; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000201:enzymology / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D012518:Sarcomeres / Q000502:physiology; D016474:Weight-Bearing
chemical_list: D000251:Adenosine Triphosphatases