What condition is indicated by muscle stiffening at extreme temperatures?

Muscle stiffening at extreme temperatures is primarily associated with rigor mortis. This phenomenon occurs after death, where the muscles become rigid due to biochemical changes in the muscle fibers, particularly the depletion of adenosine triphosphate (ATP). Without ATP, muscles cannot relax after contraction, leading to a state of stiffness.

Rigor mortis typically starts a few hours after death and can be influenced by environmental conditions, including temperature. In cooler temperatures, rigor mortis can appear later and may last for an extended period, while in warmer temperatures, it can onset more quickly and resolve sooner. This makes rigor mortis a critical factor to consider in forensic investigations when determining the time of death based on the condition of the body.

The other options delve into different biological processes or conditions: muscle atrophy pertains to the wasting away of muscle tissue, hypothermia is a dangerous drop in body temperature affecting metabolic processes, and laceration refers to a torn or ragged wound. None of these conditions specifically involve muscle stiffening as a direct and defining characteristic like rigor mortis does.