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Hypothermia and Frostbite

Hypothermia is a sudden drop in body temperature that can kill you. If you dress properly and exercise vigorously enough, it should never happen to you. Your body sends you signals as your temperature starts to drop. With a one-degree drop in temperature, your speech becomes slurred. This, in itself, is not dangerous, and occurs when people stay out in temperatures below 35 degrees, but it serves as a warning that you are losing more heat than your body is producing. To protect yourself, you can produce more heat by exercising harder or you can conserve heat by adding more layers of clothes. With a drop of three degrees, you'll find it difficult to coordinate your fingers. Seek shelter immediately. When your temperature drops five degrees, you won't be able to walk and you'll stumble and fall and not be able to get up. Then you may not be able to get out of the cold and your body temperature can continue to drop rapidly and you can die. If your clothes are wet, your temperature will drop even faster. Take the warning signals seriously; if you have slurred speech or difficulty using your hands, take action or you may not get another chance.

Frostbite means that your skin is frozen. You have plenty of warning before that happens. Your normal skin temperature is around 90 degrees. As your skin temperature starts to drop, blood vessels close and your skin turns white. When the temperature reaches 59 degrees, your body attempts to rewarm your skin by opening the blood vessels, causing your skin to tingle, itch, burn and turn red. When this happens, get out of the cold. If you don't, the blood vessels in your skin will close down again and your skin temperature can drop below 30 degrees and start to freeze.


Dear Dr. Mirkin: I’ve started to exercise, but so far I haven’t lost any weight. What am I doing wrong?

When people start an exercise program, some lose a lot of weight, while others lose nothing. An effective exercise program for weight loss should be 1) continuous, 2) use all of your major muscle groups, 3) include one intense workout a week for each muscle group, and 4) be done on land, rather than in the water. Stop-and-start exercises, such as lifting weights, do not require that you use your muscles continuously enough to burn a lot of calories. Those that use just one muscle group, such as doing situps or pushups, won't help you to lose a lot of weight because the stressed muscle groups tire quickly so you can't exercise very long.

Exercising at a leisurely pace won't help you lose a lot of weight either. You burn calories while you exercise and after you finish exercising. Intense exercise raises body temperature which continues to be elevated and burn more calories for several hours after you finish exercising. This also explains why swimming is not the best exercise for weight loss, because water conducts heat away from your body so fast that your temperature does not rise. When you exercise on land, air insulates your body so your temperature rises.

Pick sports in which you can exercise intensely, but don't exercise very hard in one sport more often than once a week. Every time that you exercise, you muscles’ fibers are torn slightly. You can tell this has happened to you when you muscles feel sore on the day after you have exercised. If you exercise intensely on days when your muscles feel sore, you are at increased risk for injuring them. Instead, alternate two sports, one that stresses your upper body and one that stresses your lower body.


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Dear Dr. Mirkin: Will fasting before a big race improve my endurance?

No. Fasting became popular because of a study that showed rats can run further after fasting than after eating. But rats are different from people. In rats, fasting increased the rate that a rat's muscles use fat, to preserve stored muscle sugar. In humans, fasting does not cause muscles to burn more fat. After fasting, human muscles continue to burn primarily their own sugar. Fasting for 24 hours uses up the same amount of muscle sugar as running for 90 minutes.

How long you can exercise a muscle depends on how much sugar, called glycogen, you can store and how long you can keep glycogen in that muscle. When a muscle runs out of its stored glycogen, it hurts and you will have difficulty coordinating it. Every time that you move a muscle, some of the stored glycogen is used up. Every time that you eat, some of the food can be stored as glycogen in that muscle. When you go for a long time without eating, you use up glycogen without replacing it. If you fast before a race, you will start that race with reduced stores of glycogen in your muscles and you will not be able to compete at your best.

It is nonsensical to claim that fasting increases endurance by causing muscles to burn more fat and less glycogen so that muscles can retain their stored glycogen longer. When you start with less glycogen, you still use it up faster and run out of fuel earlier. You can increase your endurance by markedly cutting back on exercise four days before your competition and eating as much or more than usual. If the competition lasts more than two hours, you should also eat and drink during the event.


Last Minute Recipe
Make up a plate of my favorite holiday confection:
Fruity Pebbles

List of Diana's Healthful Recipes

June 26th, 2013
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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