Heat stiffening occurs when person exposed at a temp of (AIIMS May 2012)
All muscle Proteins in the body get coagulated at temperature above 1490F (650C). Therefore, whenever a body is subjected to intense heat as by burning or exposure to high voltage current or immersion in a hot liquid, a rigidity develops due to coagulation of muscle proteins, which is usually more intense than the rigor mortis. Changes in the posture, particularly of the limbs, may occur due to contraction of the muscles (Pugilistic or Boxer’s attitude). This heat stiffening cannot be broken down by extending the limbs as in rigor mortis and will persist until disintegration supervenes. Further, unlike rigor, heat-stiffening is associated with considerable shortening of muscle Fibres . These changes have nothing to do with the life or the cause or manner of death in any way.