Muscle force transients from a dynamic distributed myocyte model

Muscle models to date comprise lumped descriptions based on the contractile element as well as crossbridge models based on bond attachment and detachment rate functions defined a priori. Both approaches are unable to describe a complete range of muscle's mechanical properties. As an alternative, a large-scale, distributed muscle model based on ultrastructural kinetics, possessing direct anatomic and physiologic relevance was developed. This model describes all of muscle's fundamental mechanical properties with a single set of assumptions, including force transients resulting from rapid changes in muscle length during contraction. Variations in muscle properties with current loading conditions arise from the dynamic model structure, rather than adaptation of a particular force-velocity curve to describe the contractile element, or of a particular bond attachment or detachment function as for previous models. This model shows how muscle's complex, nonlinear mechanical properties may arise from the sarcomere's ultrastructural dynamics.