Heat stroke, which reportedly led to the death of Vikings lineman Korey Stringer, occurs when major organs shut down from limited blood supply. People think of strokes as cerebral hemorrhages, when a certain part of the brain loses blood and produces a weakness or paralysis on one side of the body or another. But heat stroke can affect organs aside from the brain.

People think conditioned athletes may be more resistant to heat stroke, but in reality they may be more susceptible because they have to serve a larger mass.

Although people confuse heat stroke and heat exhaustion, there is a huge difference between the two. Heat exhaustion is associated with dehydration. The body can perspire and lose enough fluid to increase the heart rate and result in light-headedness. Although a person can get heat exhaustion on the way to heat stroke, heat stroke is related to elevated core temperatures in the body and the body's inability to cool itself through perspiration. When someone perspires, the body shunts blood away from major organs toward the skin as a cooling mechanism.

The warning signs for heat stroke would be the same general things associated with hypothermia: vomiting, nausea, shortness of breath, light-headedness, weakness and cramps. The key to avoiding heat stroke is hydration and monitoring core temperature. In many hospital operating rooms, core temperature can be controlled through the temperature of both IV fluids being administered and the air being ventilated to the patient.

For a football player wearing a uniform and pads, the core temperature can elevate when the humidity and the heat index are high enough to prevent proper bodily ventilation. Depending on the athlete's age and physical condition, major organs can stop functioning if the body temperature gets above 104.5-105 degrees.

Most athletes are in great condition, but they also have larger muscles -- including the heart. Because the organs are so well-developed from conditioning programs, they require more blood supply and oxygen to keep them functioning. People think conditioned athletes may be more resistant, but in reality they may be more susceptible because they have to serve a larger mass.

A large man like the 330-pound Stringer would be more likely to suffer heat stroke than a slighter person because his body has to cool a greater mass. Covering the surface area with a uniform, pads or sweats further limits the body's ability to cool down.

The most important thing a trainer can do during preseason workouts is to monitor the heat index. On hot, humid football fields at Florida, Auburn and Mississippi, I have seen trainers use hand-held devices. When the heat index rises to a certain point, college trainers will often go to the head coach and tell him the heat index is too high to practice. The coach can then either stop practice, move the practice indoors or give the players a break to cool down and rehydrate.

Unfortunately, there are places where people think athletes may not be subjected to the same level of heat and humidity as they are in the South. Like believing you won't get sunburned on an overcast day at the beach, the heat index can sneak up and be more harmful when it's not anticipated. At the same time athletes push their bodies to the limits during training camp, and the body can only take so much.

Medically, everybody's body is wired differently. At medical school, when students go to the anatomy labs and look at the cadavers, the medical books tell them where the organs are. But in reality, one body is not like another. That's why predicting what happened to Hank Gathers or Stringer is next to impossible.

People want to point fingers at trainers and doctors to say they should have seen it coming, but there is no way of knowing Stringer's body would react the way it did. It's called "the practice of medicine" because a doctor is practicing and doing the best he can to take all the information and variables from person to person and estimate the best course of action. But there is no perfect recipe, for Stringer or anyone else.

Dr. Jerry Punch, a pit reporter for ESPN's auto-racing coverage since 1984 and a college football sideline reporter, serves as the director of emergency-room services at Memorial Hospital-Flagler in Bunnell, Fla.