FIGURE 2.

Analysis of degrees of freedom immediately following the end of stretch. A, 32 μmol/liter of Ca²⁺. B, 1 μmol/liter of Ca²⁺. Data are shown in black. The time axis was reset so that zero marks the time at which the stretch ends (0.7 s in Fig. 1). As in Fig. 1, the passive force in the presence of BDM has been subtracted from the observed force signal. At 32 μmol/liter of Ca²⁺ the force decay was fit by a single exponential with a rate constant of k = 58.9 ± 0.2 s⁻¹ and amplitude A = 12.30 ± 0.03 kN m⁻² (χ²/DoF = 0.0029; R² = 0.992), shown as the red line. At 1 μmol/liter of Ca²⁺, the force decay was fit by a double exponential, with one rate constant set at the same value as that seen at 32 μmol/liter of Ca²⁺, namely k₁ = 58.9 s⁻¹ with the fit parameters being A₁ = 8.09 ± 0.03 kN m⁻², k₂ = 10.00 ± 0.10 s⁻¹, A₂ = 5.16 ± 0.02 kN m⁻² (χ²/DoF = 0.016; R² = 0.997).