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Why Does the Body Temperature Increase When Exercise Is Done?

Every cell in your body that has a nucleus has a microscopic biological furnace system in it. Almost all your cells have at least one nucleus and skeletal muscle cells have several. Skeletal muscles are the ones you use in exercise -- the muscles that you can move as you choose. They have multiple nuclei and more than one furnace per cell to fuel the muscle fibers. Even though these cellular furnaces produce no flames, they do produce heat, which is why you may notice an increase in your body temperature after an intense workout.

All warm-blooded animals seek to maintain a body temperature that is normal for their species. According to “The Merck Manual Home Edition,” humans usually are within a degree or two of the traditional average of 98.6. F. This varies by individual and you can check your temperature in the morning before any activity to know your own normal temperature range. Men often have slightly higher temperatures than women of the same age because they tend to have a higher metabolic rate.

An area in the brain called the hypothalamus is responsible for temperature regulation and responds to chemical signals from the body. One of these is the response to an invader such as a virus: The hypothalamus turns up the heat to try to kill the invader. The fever builds until it reaches the point where it can damage the brain, then the fever typically breaks, you sweat profusely and your body cools down to near normal. If you are in danger from an outside source, the signal is to the adrenal glands for the fight or flight response. The surge of adrenaline makes your heart beat faster and pump more blood into the muscles so that you can react quickly. When the danger passes, you might feel as tired as if you had exercised.

When you exercise, you take your body by surprise in a sense. You are using the muscles and they require oxygen to function, and the body responds with more frequent and forceful heartbeats to supply it. You also begin to breathe more rapidly to take in more oxygen. Your pores are closed, so the heat builds up in your body. The hypothalamus will respond and turn down the heat by opening the pores so that you sweat. Your temperature will go back to normal, but for a time it might be above your normal right after you exercise. You will notice that your heart rate and blood pressure also rise after a strenuous workout.

A rapid return to a normal heart rate, blood pressure and temperature after exercise shows that your body conditioning is working. You might soon be ready for the next step in your program. Besides the muscle conditioning and cardiovascular benefits, there is an important thing to remember about exercise: All that heat produced by those tiny furnaces requires fuel. The fuel is glucose, which is produced by your liver from the foods you eat. You are burning calories. If you burn more calories than you take in, you will lose weight; if you exercise, you also will firm and tone your body.

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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.