Saturday, January 14, 2006

Body Temperature During Exercise

Heat stroke is a concern primarily during hot weather, but in the relatively cool environmental temperature of 50 F, healthy marathon runners can have body temperatures as high as 103.8 F. Weight lifters often have temperatures of 101 F during workouts in a warm gym. One runner who was still conscious is reported to have developed a temperature of 107.8 F after finishing a marathon, but most people cannot tolerate temperatures that high.

You suffer heat stroke when your body temperature rises so high that it cooks your brain, causing you to pass out. This is particularly likely to happen when you exercise, particularly in hot weather, because food is converted to energy by a series of chemical reactions, each of which release heat. The sum of the reactions convert more than 80 percent of the energy into heat, while less than 20 percent is actually used to drive your muscles. That means that the harder you exercise, the higher your temperature can rise, and your body has to work very hard to keep your body from overheating. During exercise, not only must your heart work extra to pump oxygen from blood in your lungs to your muscles, it must also pump heat in blood from your muscles to your skin where you sweat and it evaporates to cool you off.

Several factors increase our chances of developing a heat stroke such as when the outside temperature and humidity are high, you are not in shape, you take certain medications or are sick or dehydrated. Aspirin does not keep your temperature from rising during exercise because aspirin lowers fever by making you sweat and it when your body temperature rises during exercise, you sweat, and aspirin does not make you sweat more.

To protect yourself from heat stroke when you exercise, start out slowly and gradually increase your pace. This gives your body time to circulate the heat to the skin where heat can be dissipated. Drink fluids long before you are thirsty. Once you are thirsty, you are already dehydrated, having lost at least 2 pounds of fluids. Drink whatever you like best at least every 15 minutes and know the symptoms of rising body temperature. When your temperature rises above 102, your muscle often start to burn, when your temperature is over 104 you will usually become short of breath and when your temperature rises above 105, you will often have signs of brain distress, such as a headache, blurred vision, ringing in your ears, dizziness, nausea and passing out.

Dr. Gabe Mirkin has been a radio talk show host for 25 years and practicing physician for more than 40 years; he is board certified in four specialties, including sports medicine. Read or listen to hundreds of his fitness and health reports at

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