Mechanism for muscle force deactivation during quick length changes

Muscle exhibits complex viscoelastic properties. Neither lumped muscle models nor ultrastructural crossbridge models have been successful in satisfactorily describing these properties, or in proposing a mechanism for their origin. A recently developed large-scale distributed model of a single muscle fiber based on myofilament kinetics is shown capable of describing all four stages of force deactivation following a quick change in muscle length during isometric contraction. In essence, this model implicates muscle's viscoelastic bonds and distributed mechanical properties as the origin of its complex dynamic behavior.<>