What is the term used for the stiffening of body muscles after death?

The term used for the stiffening of body muscles after death is rigor mortis. This physiological phenomenon occurs as the muscles' chemical processes change following the cessation of life, leading to stiffening and loss of elasticity. After death, the body experiences a depletion of ATP (adenosine triphosphate), which is essential for muscle relaxation. As ATP levels decline, the actin and myosin filaments within the muscle fibers remain in a contracted state, resulting in stiffness. Rigor mortis typically starts to become noticeable within a few hours after death and can last for up to 48 hours, after which the body begins to undergo decomposition.

Other terms such as postmortem relaxation refer more to the processes that occur after rigor mortis has passed, while necrosis is more associated with the death of living tissue due to injury or disease. Cadaveric spasm is a phenomenon that may occur immediately at the time of death, often associated with violent deaths, but it is distinct from the general stiffening described by rigor mortis. Understanding rigor mortis is crucial in forensic science and can assist in determining the time of death during an investigation.