Figure 1.

Assessment of myofilament Ca²⁺ response variability. Top: Force-pCa²⁺ relationship curves showing variations in myofilament Ca²⁺ sensitivity. The solid line represents the baseline force-Ca²⁺ relationship. Curve (A) demonstrates increased Ca²⁺ sensitivity, indicated by a leftward shift, where a given steady-state force is achieved at lower Ca²⁺ concentrations. Curve (B) demonstrates decreased Ca²⁺ sensitivity, indicated by a rightward shift, requiring higher Ca²⁺ concentrations to generate the same steady-state force. Bottom: This panel shows a biochemical representation of the Ca²⁺ binding dynamics to Troponin C (TnC). It includes the calcium association rate (k_on) and dissociation rate (k_off) from TnC, alongside a formula illustrating the relationship between the equilibrium dissociation constant (Kd), k_on, and k_off.