Strong binding cross-bridges reduce the activation dependence of the rate of force redevelopment in murine ventricular myocardium. The rate constant of force redevelopment was determined in the permeabilized murine ventricular myocardium in the absence (filled circle) and presence (empty circle) of 1 μM NEM-S1. Data points are means and the error bars are the SEM. (A) The rate constant of force redevelopment was recorded as a function of relative steady-state force (P/P_o) measured at each pCa. Note the significant increase in the rate of force redevelopment at low levels of Ca²⁺ activation following NEM-S1 treatment. (B) Relative force–pCa (filled circle) and relative ktr–pCa (empty circle) relationships were determined in permeabilized myocardial preparations isolated from murine ventricular myocardium following treatment with 1 μM NEM-S1. Data points are means and the error bars are the SEM.