Two-state fit. Simulations fitted to tension-recovery records measured with chemically permeabilized myocardial samples. The calculations used a two-state model similar to that shown in Fig 1 A but with a strain-dependent detachment rate function. The model parameters are listed in full in Table S2. Panels show (A) predicted force records, (B) the proportion of binding sites that are available (solid lines) and that are bound (dotted lines), and (C) the half-sarcomere lengths. The imposed length change is shown by the dotted line. The left-hand axes show the entire simulation. The right-hand axes show the response to the length perturbation on an expanded time scale. (D) The simulated force records overlaid on the experimental force records (black lines). The gray regions around each line show the standard error of the experimental data.