Final answer:
The myosin head tightly bound to the actin molecule is referred to as the Rigor state. In this state, the myosin head is still bound to actin after the power stroke.
Step-by-step explanation:
The state in which the myosin head is tightly bound to the actin molecule is referred to as Rigor state. In this state, the myosin head is in a low-energy position and still bound to actin after the power stroke. ATP can then attach to myosin, allowing the cross-bridge cycle to start again and further muscle contraction can occur.