Heat stiffening occurs at temperature above:

Heat stiffening occur when a body is exposed to temperatures above 65 degree celsius. In this condition, rigidity is produced which is more marked than rigor mois. Heat stiffening occur because of denaturation of muscle proteins. Degree and depth of stiffening depend on the intensity of heat and the time for which it was applied. It is seen in death from burning, high voltage electric shock and from falling into hot liquid.