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Sugar Before Exercise

For more than 20 years, athletes were told to avoid sugary meals within three hours of a competition. In 1977, researchers found that eating sugar within three hours of exercising caused blood sugar levels to shoot sky high and then to fall to low levels. Eating sugar causes blood sugar levels to rise. Your pancreas responds by releasing large amounts of insulin which remain in your bloodstream when you start to exercise. The insulin already in your bloodstream plus muscles drawing large amounts of sugar from your bloodstream can cause your blood sugar to drop to very low levels. Since 99 percent of the energy for your brain comes from blood sugar, it was felt that your brain would suffer from lack of an energy source and you would feel terribly tired and pass out. Low blood sugar levels cause tiredness and passing out, but athletes are able to tolerate extremely low blood sugar levels during competitions without even slowing down.

More recent research has shown that eating sugar prior to competition can enhance performance. The extra calories are there to continue fueling your muscles. You should eat one to five hours prior to competition and you can eat sugary foods. Your only concern is that your stomach should be relatively empty when you start to exercise, so some athletes avoid fatty foods that stay in the stomach for a longer time. Easily-digestible pre-event foods include fruits and fruit juices, breakfast cereals with skim milk, muffins, bagels and so forth.


Dear Dr. Mirkin: Is it safe to use a hot tub in a hotel or health club?

It’s extremely unlikely that you will pick up a viral infection in the hot tub, but you can get folliculitis, a bacterial infection. Viruses such as herpes are killed almost immediately in chlorinated water. The herpes virus can survive for up to four or five hours on the edge or seats that are not underwater. However, even if you sit on the same spot that a person with active herpetic blisters has just left, you probably wouldn't be infected. To acquire herpes, you need to allow the virus to pass through broken skin.

Hot tubs that have not been adequately chlorinated can give you folliculitis, a condition that causes severe itching and red bumps on the skin. It can be cured with antibiotics, but often goes away by itself without treatment. If you use public hot tubs, pools and whirlpools, sit on a towel on the side of the tub or pool, and shower immediately after you leave the water. If you start to itch, check with your doctor.


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Dear Dr. Mirkin: What’s the best exercise to strengthen my heart and give me large muscles?

I can’t think of any single exercise that will do all that. To strengthen your heart muscle, you have to exercise vigorously enough to make your heart pump more blood. This means your exercise must speed up your heart rate and keep it elevated for a while. The formula for heart-lung fitness is to exercise vigorously enough to raise your heart rate at least 20 beats a minute above your resting rate, and try to work up to 30 minutes, 3 times a week. If you can't exercise continuously for thirty minutes, exercise, stop when you feel tired, and repeat the cycle.

To strengthen your skeletal muscles, you have to exercise against increasing resistance, such as lifting heavy weights or pushing against special strength-training machines. The greater the resistance without causing injury, the greater the gain in strength. However, when you exercise against resistance, your muscles fatigue very rapidly. If you exercise against resistance for more than 50 continuous seconds, you increase your risk of tearing your muscles. You cannot maintain resistance that is needed to increase skeletal muscle strength significantly for the longer periods needed for heart strength.

You could pick a sport such as cycling for heart muscle fitness, and then climb lots of steep hills to provide resistance to strengthen your muscles. However, cycling stresses primarily the upper legs, so you would still need another activity to strengthen your other skeletal muscles. It’s better to pick a sport you enjoy to strengthen your heart, such as running, fast walking, swimming, cycling, dancing or any other continuous exercise. To strengthen your skeletal muscles, use weights or special strength-training machines. A good program would include cycling or running on Mondays, Wednesdays and Fridays and using strength machines on Tuesdays and Thursdays.


This week we have three tasty RECIPES contributed by readers:
Michael’s Eggplant Sauce for Whole Grains
Ruth’s Quickest Rice Pudding Yet
Alan’s Faux Mueslix

If you have a healthful recipe you’d like to share, please send it to

List of Diana's Healthful Recipes

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

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