An alternative mechano-chemical model of muscle contraction is proposed. The model combines interaction among four elements: chemical kinetics of the acto-myosin ATPase pathway, Ca2+ binding kinetics, mechanical coupling during Pi release, and working stroke motion to constitute simultaneous relations among mechanical and chemical variables. The model proposes that ADP can be released from both a high strain and a low strain state, though at different rates for the two cases. The model is derived from a different basis than the classical Huxley model. Force developed from strongly attached cross-bridges is related to chemical component concentrations, chemical equilibrium and rate constants for the ATPase activity, and velocity of contraction. The chemical dynamics of the ATPase activity is also related to the velocity of contraction. A model for Pi release during force generation and a model for chemical-mechanical coupling transition during a working stroke are also proposed and are the important keys of the mechano-chemical linkage in energy transduction and muscle dynamics. The steady force-velocity relation is predicted by only one dimensionless parameter, and it provides an excellent fit to the Hill force-velocity equation. The model is able to simultaneously predict the peak in the ATPase activity as a function of the velocity of contraction and supports the argument of multiple cycles of cross-bridge attachment per one ATP molecule hydrolysis. Also the relation between the amount of Ca2+ and the force development can be predicted from this model.

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