Measured parameters of Cross-bridges. *P value ≤ .05 compared to nfTm; ^**P value ≤.01 compared to nfTm; else, P value > .05. Other than rigor stiffness, all parameters were measured in the standard activating solution. is the steady-state active tension. Tension and stiffness were normalized against the actin filament tension in the standard activating solution at 25°C ( = 9.0 ± 0.9 kPa, ±SEM, N = 52). To deduce , 5 frequency points around the minimum are fitted to the cubic equation with 4 constants. corresponds to the rate constant of phase 3, and corresponds to that of phase 2 of step analysis [32]. In all experiments, temperature was 25°C, ionic strength 200 mM, and pH 7.00. The rigor stiffness was measured at 100 Hz. The data were individually fitted to respective equations, averaged, and tabulated with ±SEM. ^†Data based on Lu et al. [13].