ABSTRACT
Adenosine triphosphate is required to power muscle contraction, but it also functions to dissociate the myosin and actin bonds after a contraction. Therefore, resting muscle is easily stretchable and extensible. However, if the ATP supply is depleted, myosin and actin form tight bonds so that the muscle filaments no longer slide over one another.[3] This inextensibility is referred to as rigor mortis (Latin for the stiffness of death). The time course of rigor mortis is directly related to the muscle ATP content (see Fig. 2). It also varies with species (beef, 12-24 hr; lamb, 8-12 hr; pig, 4-6 hr; chicken and turkey, 2-3 hr). The time course is also related to the muscle temperature, with glycolysis generally more rapid at higher temperatures.
