Tight versus loose coupling in a DM model of calcium activation dynamics

Previous representations of calcium activation (or active state) in muscle models have assumed that the time course of activation is independent of the time course of contraction. In constructing a calcium-activation model for the distribution-moment (DM) model of muscle, the authors developed two versions: loose coupling between calcium-troponin and actin-myosin interactions, or tight coupling between these interactions. Only under loose coupling is activation independent of contraction. Both direct experimental evidence and simulation results indicate that the tight-coupling version is to be preferred.<>