Figure S23.

Effect of changes in baseline calcium level on resting and twitch tension. In all simulations with cross-bridge cycle without PS (i.e., five-state model), the calcium transient (dashed pink line) with baseline [Ca²⁺] levels was reduced from observed values of 0.143 µM to 0.05 µM. MUSICO simulations with the observed [Ca²⁺] transient (dark pink line) with the same model parameters as shown in Fig. S22 predicted significantly elevated resting tension, slightly higher peak tension, and slower tension relaxation rate (dark green line). After returning to low [Ca²⁺] levels (i.e., at time >0.4 s), tension remains about the same as the resting tension. For reference, the twitch tension response to [Ca²⁺] transients with reduced baseline [Ca²⁺] level is shown as a green line.