FIGURE 9.

Elastic and viscous moduli measured at maximum calcium activation and varying free Mg²⁺ concentrations. A and B, characteristic dips and peaks of the elastic and viscous moduli were shifted to lower frequencies as free Mg²⁺ concentration was elevated. The repeat measurement at 2 mm free Mg²⁺ indicates that these effects were reversible. C, myosin cross-bridge detachment rate was detected by analysis of the frequency characteristics of the elastic and viscous moduli and was found to be reduced with increasing free Mg²⁺ concentrations. D, corresponding cross-bridge time-on was prolonged with increasing free Mg²⁺ concentrations. E, developed isometric tension was not significantly affected by Mg²⁺. One-way analysis of variance demonstrated significance at p < 0.01 level for detachment rate and time on. rep = repeat. *, p < 0.05; **, p < 0.01 compared with 1 mm condition, and †,p < 0.01 compared with 8 mm condition by paired t test. n = 4 strips.