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Intervals to Improve Endurance

Most coaches and researchers are convinced that you have to do a series of short bursts of very fast speed training to improve long-term endurance, but they do not know why. The most offered explanation is that muscle fatigue caused by many hours of cycling is associated with a reduction in muscle fibers’ ability to contract with force. Now a study from France shows that short bursts of very fast cycling improve endurance for cycling competitions that take many hours, because the stronger you are, the less of your maximal effort is needed to get the same pressure on the pedals (Medicine and Science in Sports and Exercise, January 2005.)

Muscles are made up of millions of individual fibers. Each fiber is a single muscular thread that functions independently. When you contract a muscle, you contract only a small percentage of these fibers at the same time. As each muscle fiber fatigues, you lose the ability to contract that fiber. When enough of these fibers stop contracting efficiently, you lose strength and your muscles feel tired. However, stronger fibers take longer to fatigue because they are being worked at a lower percentage of their capacity. So stronger muscles can be exercised for longer periods of time.

Making each muscle fiber stronger and bigger allows it to exert force for a longer period of time and therefore, increases endurance. The only way to make a muscle stronger is to exercise that muscle against progressively greater resistance, and that applies to each muscle fiber also. It is impossible to put great pressure on a muscle for a long time. When you do all-out fast bursts for a short time, you exert so much pressure that you have to back off after several seconds or a minute. All-out sprints for a short period followed by resting and then repeating the sprint is called interval training. It makes the entire muscle stronger and delays fatigue.

Athletes in all sports use long and short intervals. Short intervals take less than 30 seconds and because you do not build up significant amounts of lactic acid in that time, you can do hundreds of repeats in a single workout. Long intervals take two to three minutes and are very damaging to your muscles. Because you feel burning in your muscles and become very short of breath for a longer time, you can do only a few of these in a single workout. So athletes in all sports that require endurance do both long and short intervals to help them exercise longer.


Follow-up on frequent urination:
Many of you asked about the nasal spray treatment I mentioned last week. It’s an antidiuretic hormone that shuts down the kidneys temporarily and is effective for both men and women. It’s called desmopressin, brand name DDAVP, available by prescription. More information


Dear Dr. Mirkin: Does the warning about belly fat and heart attack risk apply to all ethnic groups?

Yes; a study reported in the November 5, 2005 issue of Lancet covered people from 52 countries and confirmed that storing fat primarily in your belly markedly increases chances of suffering a heart attack in all groups. Some regions and ethnic groups appear to be more disposed to this pattern of fat distribution and their heart attack rate is correspondingly higher. When you store fat primarily in your belly, you also store it in your liver. After insulin does its job of driving sugar from the bloodstream into your cells, it is supposed to be removed by your liver. Having a lot of fat in your liver prevents your liver from removing insulin, causing blood levels of insulin to rise too high. Insulin constricts arteries to cause heart attacks. It also acts on your brain to make you hungry so you eat more. It acts on your liver to manufacture more fat and it causes fat to be deposited in the fat cells in your belly.

Storing fat on your hips, or in both your belly and your hips, does not increase risk for suffering heart attacks. The researchers conclude that larger hips are often associated with greater muscle mass, and strong muscles help to protect you from heart attacks.


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Dear Dr. Mirkin: Is Helicobacter the only bacteria that causes stomach ulcers?

Barry Marshall won the 2005 Nobel Price in Medicine for proving that stomach ulcers are caused by bacteria called Helicobacter pylori. Several papers have shown that a type of stomach cancer called MALT is caused by the same bacteria that causes stomach ulcers and that many cases of MALT stomach cancers can be cured by taking antibiotics to kill Helicobacter. An exciting report from Austria shows that antibiotics can cure the stomach cancer even though it is not caused by Helicobacter (Gut, November 18, 2005.) So far, researchers have shown that more than 25 different bacteria can cause stomach ulcers, and doctors do not have the ability to test for all of these bacteria. Doctors cured this case of stomach cancer with metronidazole, clarithromycin and an antacid. I believe that anyone with symptoms of stomach distress should be given a trial with the triple therapy used to treat Helicobacter, even if the tests for Helicobacter are negative. More information


Recipe of the Week:
Quick Shrimp Curry

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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