Relationships between isometric and isotonic mechanical parameters and cross-bridge kinetics

1. Isometric and isotonic measures have been widely used both to characterize muscular contraction in striated muscle and to compare the mechanical properties of striated muscle types for a wide variety of species. The interrelationship of these measures and their interpretation, in terms of underlying cross-bridge mechanisms, requires clarification. 2. We demonstrate that a strain-dependent three-state model can simulate these isometric and isotonic mechanics and offer a unified explanation for these mechanics in terms of crossbridge kinetics. 3. Our exploration reveals the partial view each individual measure of mechanics provides and emphasizes the complementary insights the various isometric and isotonic measures give of the underlying cross-bridge kinetics.