What term describes the involuntary stiffness of the body after death?

Rigor mortis refers to the physiological process that occurs after death, characterized by the stiffening of the body's muscles. This stiffening results from biochemical changes in the muscle tissues that take place once the heart stops beating and oxygen supply ceases. After death, the body no longer produces adenosine triphosphate (ATP), which is necessary for muscle relaxation. Consequently, the muscles become rigid and remain in that state for a period, typically beginning a few hours after death and lasting up to several days, depending on environmental conditions.

This process is significant in forensic science, as it can help determine the time of death. Rigor mortis is a systematic and predictable progression of body stiffness, making it a key indicator for professionals in identifying postmortem changes.

In contrast, postmortem lividity involves the pooling of blood in the lowest parts of the body due to gravity, cadaveric spasm signifies an instantaneous stiffening of the muscles at the moment of death, often related to violent deaths, and algor mortis refers to the cooling of the body after death. Each of these terms describes different aspects of the changes that occur in a body postmortem, but rigor mortis specifically addresses muscle stiffness.