Three-state model predictions for transient velocities and cross-bridge distributions after quick release to isotonic force at F/F_o = T/T_o = 0.4 or at steady-state shortening velocity of 445 nm/s (i.e., 0.29 of v_max). (A) Evolution of velocities after quick release to isotonic force of F/F_o = 0.4 predicted by MUSICO (black line), Duke (green line), and Duke PL (red line). The displacements after release are the same because the SE components of Duke and Duke PL models match the effect of the myosin and actin filaments from MUSICO (right inset). The velocity transients during the first 20 ms after release are shown in the left inset. (B) Velocity evolution after release to the F/F_o values at which all models have the same steady-state shortening velocity of 445 nm/s. In the left inset are shown velocity transients during the first 20 ms after release and in the right inset the displacements after release. (C) Cross-bridge distributions and state probability density distribution functions at times t_QRel = 20 ms after release to F/F_o = T/T_o = 0.4 (left column) and to F/F_o = T/T_o, which have the same steady-state velocity of ∼445 nm/s (right column).