title: The passive properties of muscle fibers are velocity dependent.
abstract: The passive properties of skeletal muscle play an important role in muscle function. While the passive quasi-static elastic properties of muscle fibers have been well characterized, the dynamic visco-elastic passive behavior of fibers has garnered less attention. In particular, it is unclear how the visco-elastic properties are influenced by lengthening velocity, in particular for the range of physiologically relevant velocities. The goals of this work were to: (i) measure the effects of lengthening velocity on the peak stresses within single muscle fibers to determine how passive behavior changes over a range of physiologically relevant lengthening rates (0.1-10Lo/s), and (ii) develop a mathematical model of fiber viscoelasticity based on these measurements. We found that passive properties depend on strain rate, in particular at the low loading rates (0.1-3Lo/s), and that the measured behavior can be predicted across a range of loading rates and time histories with a quasi-linear viscoelastic model. In the future, these results can be used to determine the impact of viscoelastic behavior on intramuscular stresses and forces during a variety of dynamic movements.
authors.affiliation: Biomedical Engineering, University of Virginia, PO Box 800759, Health system, Charlottesville, VA 22908, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Rehorn
authors.affiliation: Biomedical Engineering, University of Virginia, PO Box 800759, Health system, Charlottesville, VA 22908, United States.
authors.forename: Alison K
authors.initials: AK
authors.lastname: Schroer
authors.affiliation: Biomedical Engineering, University of Virginia, PO Box 800759, Health system, Charlottesville, VA 22908, United States; Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA 22908, United States. Electronic address: ssblemker@virginia.edu.
authors.forename: Silvia S
authors.initials: SS
authors.lastname: Blemker
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D004548:Elasticity / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology*; D017711:Nonlinear Dynamics; D013314:Stress, Mechanical; D014783:Viscosity; D016474:Weight-Bearing / Q000502:physiology
keywords: Muscle fiber mechanics; QLV model; Viscoelasticity