Figure 7. Force trajectories predicted by the simulation model during release from isometric contraction to isovelocity shortening early in a tetanus (Aa and b; release when force = 5 %F_o), during the plateau of the tetanus (Ba and b) and early in relaxation (Ca and b; release when force = 90 %F_o).

The right column shows the shortening part of the response on an expanded time base. The activation time constant (τ_on) was 20 ms, the inactivation time constant (τ_off) was 50 ms. The dahsed line in A is the rise of isometric force predicted by the model for instantaneous activation of cross-bridge binding sites.