The four steps of muscle contraction are EXCITATION, COUPLING, CONTRACTION AND RELAXATION.
Muscle excitation involves the generation of action potential in the muscle cell membrane as a result of stimulation. Coupling refers to the linking of the action potential to the myofilament in readiness for contraction. During contraction, the muscle fibers experience tension and usually become shorten. Relaxation refers to the resting stage of the muscle fiber.