Heat is the most severe physiological stress placed on the body during exercise. The entire paradigm of athletic performance and athletic injury prevention centers on warming the body in preparation for exercise. This means that athletes are intentionally placing their body into hyperthermia each time they exercise. Heat stroke occurs when the body loses its ability to cool itself when placed into hyperthermia. There is not a single cause of heat stroke likewise there can obviously not be a single determination of when it is safe to resume exercise after heat stroke. Heat stroke does not just affect the brain it also affects the other life sustaining vital organs.
What is known is that it is not necessary how hot the body gets during heat stroke, but how long it stays over heated. During this period of hyperthermia, blood is directed towards the skin in an attempt to cool. This deprives the internal organs of oxygenated blood which may or may not result in permanent damage. In many ways, this may be considered a metabolic cascading injury similar to cerebral concussions. Various medical organizations including the American College of Sports Medicine and the National Athletic Trainers’ Association have position statements concerning heat stroke, but there still is not a definitive answer to when an athlete can “return to play”.