The two-state A.F. Huxley 1957 model
The two-state A.F. Huxley 1957 model has only two states: detached when the heads can freely move and attached when a myosin head is attached to actin and can only move with actin. The state transition rates between the detached and the attached sate is defined as
and between attached and detached rate as:
where is the axial component of crossbridge strain, is the range for positive probability of attachment (Huxley, 1957), is the Zahalak factor (Zahalak, 1986) which accounts for higher detachment rates during lengthening for crossbridges stretched more than .