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友人John運動時不斷地流汗，而且覺得很熱，體溫很高；於是我就上網做了一些調查，－－運動時體溫的確會升高。

沒想到運動時身體將食物轉化為我們運動所需的能量，這當中竟然有80%是以熱量的形式釋放出來，而非貢獻於運動中。在較涼的環境中(攝氏十度)馬拉松選手的體溫可以升高到將近40度，曾有報告指出：一個馬拉松選手在完成比賽後，神智清醒的情況下，體溫高達近42度； 可是大部分的人體溫如果飆到42度都已經昏迷了。

台灣的夏天炎熱潮濕，預防中暑很重要。除了天候因素外，身體的狀況不好、生病、服用藥物、或脫水都是造成中暑的危險因子。因天候或運動等因素導致的發熱是無法以阿斯匹靈來降溫的，因為Asprin是以讓身體流汗的方式來降溫。


要注意水分的補充。

預防中暑的方法：

1. 循序漸進慢慢增加強度。

2. 在口渴之前就喝水：當覺得渴時，你已經流失近900克的水了，最好是每15分鐘喝一次水。並避免喝含有酒精與咖啡因的飲料，如果要運動超過一小時，最好喝運動飲料。

3. 注意自己體溫升高的情形：通常體溫在38.9度，時肌肉已經開始燃燒。40度就會有呼吸困難；40.5度以上則會有頭痛、視力模糊、耳鳴、噁心想吐等症狀。

4. 適當的穿著　基本上較寬鬆的衣服較有助於排熱　避免深色衣服

5. 避免在烈日下運動

6. 擦防曬油 曬傷會降低身體的排熱功能

注意身體的警訊：

 
High Body Temperature during Exercise

Gabe Mirkin, M.D.

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.

In the relatively cool environmental temperature of 50 F (10ºC), healthy marathon runners can have body temperatures as high as 103.8 F (39.89ºC). Weight lifters often have temperatures of 101 F (38.33ºC) during workouts in a warm gym. One runner who was still conscious is reported to have developed a temperature of 107.8 F (42.11ºC) after finishing a marathon, but most people cannot tolerate temperatures that high.

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 (38.9º C), your muscle often start to burn, when your temperature is over 104 (40º C) you will usually become short of breath and when your temperature rises above 105 (40.56ºC), you will often have signs of brain distress, such as a headache, blurred vision, ringing in your ears, dizziness, nausea and passing out.

http://www.drmirkin.com/fitness/9638.html


Hot-weather exercise: How to keep cool

Outdoor exercise can be challenging when the temperature soars. Stay safe during hot-weather exercise by drinking enough fluids, wearing proper clothing and timing your workout to avoid extreme heat.

In the excitement of a pickup basketball game or the relaxation of a friendly round of golf, you might not notice the temperature rising — but your body will. If you exercise outdoors in the heat, use caution and common sense to prevent heat-related illnesses.

How hot weather affects your body

Exercising in hot weather puts extra stress on your heart and lungs. Both the exercise itself and the air temperature increase your body temperature. To dissipate heat, more blood circulates through your skin. This leaves less blood for your muscles, which increases your heart rate. If the humidity is high, your body faces added stress because sweat doesn't readily evaporate from your skin — which only pushes your body temperature higher.

Under normal conditions, your skin, blood vessels and perspiration level adjust to the heat. But these natural cooling systems may fail if you're exposed to high temperatures and humidity for too long. The result may be a heat-related illness, such as heat cramps, heat exhaustion or heatstroke.

How to avoid heat-related illnesses

To keep it cool during hot-weather exercise, keep these basic precautions in mind:

Take it slow. If you're used to exercising indoors or in cooler weather, take it easy at first. As your body adapts to the heat, gradually increase the length and intensity of your workouts. If you have a chronic medical condition or take medication, ask your doctor if you need to take additional precautions.

Drink plenty of fluids. Your body's ability to sweat and cool down depends on adequate rehydration. Drink plenty of water while you're working out — even if you don't feel thirsty. If you're planning to exercise intensely or for longer than one hour, consider sports drinks instead. These drinks can replace the sodium, chloride and potassium you lose through sweating. Avoid drinks that contain caffeine or alcohol, which actually promote fluid loss.

Dress appropriately. Lightweight, loosefitting clothing promotes sweat evaporation and cooling by letting more air pass over your body. Avoid dark colors, which can absorb the heat. A light-colored hat can limit your exposure to the sun.

Avoid midday sun. Exercise in the morning or evening — when it's likely to be cooler outdoors — rather than the middle of the day. If possible, exercise in the shade or in a pool.

Wear sunscreen. A sunburn decreases your body's ability to cool itself.

Have a backup plan. If you're concerned about the heat or humidity, stay indoors. Work out at the gym, walk laps inside the mall or climb stairs inside an air-conditioned building.

Know when to call it quits

During hot-weather exercise, be on the lookout for heat-related illness. Signs and symptoms may include:

Weakness
Headache
Dizziness
Muscle cramps
Nausea or vomiting
Rapid heartbeat

If you suspect a heat-related illness, stop exercising and get out of the heat. Drink water, and wet and fan your skin. If you don't feel better within 60 minutes, contact your doctor. If you develop a fever higher than 102 F (38.9 C) or become faint or confused, seek immediate medical help.

Regular physical activity is important — but don't let hot-weather workouts put your health at risk.

http://www.mayoclinic.com/health/exercise/hq00316

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The articles were taken from webites of Dr.Mirkin.com and MayoClinic.com at the URL stated behind each article respectively.  The copyright remain with their original owners.  The Dr.Mirkin.com and MayoClinic are not involved with, nor endorse the production of this blog.