ALT Human β-cardiac myosin shifts in equilibrium between two states: an open-headed structure, or active state, available for actin cross-bridge formation and a folded back, or super-relaxed (SRX) state, not available for the interaction with actin filaments. Mavacamten and CK-274 shift this equilibrium toward the SRX state, ultimately reducing contractility, in the opposite way omecamtiv mecarbil stabilizes the active state, thereby increasing contractility.