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Exercise Lowers Salt Sensitivity

Excessive intake of salt causes high blood pressure in some, but not all, people. High blood pressure increases risk for heart attacks, strokes, and kidney damage. Why do some people develop high blood pressure when they take in a lot of salt, while others do not? A recent study from the University of Minnesota shows that middle-aged people who start an exercise program lose their tendency to develop high blood pressure when they take in extra salt (Journal of Human Hypertension, May 2006).

All people who exercise frequently and hard need to take in extra salt. During World War II, Dr. James Gamble of Harvard Medical School showed that the only mineral that exercisers need in large quantities is salt. If heavy exercisers don’t take in enough salt, they will eventually run low on salt and suffer fatigue, muscle aches and cramps, and be at increased risk for injuring themselves.

The Minnesota study measured blood pressure in people when they followed a high-salt diet and again when they went on a low-salt diet. The salt-sensitive people who developed high blood pressure on a high-salt diet were started on an exercise program. After six months, many of these people did not develop high blood pressure when they again ate a high-salt diet. This shows that regular exercise can control high blood pressure caused by a high-salt diet. Previous studies show that it is very bad advice to tell most exercisers to restrict their intake of salt. This new study shows that many people who develop high blood pressure from a high salt diet when they are sedentary, will not develop high blood pressure on the same diet when they exercise.


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Dear Dr. Mirkin: I’m sixty; is it too late to strengthen my bones with exercise?

Every American woman, and most men, will suffer from osteoporosis if they live long enough. Hip bones broken by osteoporosis do not heal, and must be replaced immediately. A study from Australia shows that regular exercise helps to keep bones strong and exercising into later life protects bones of older people even more (Journal Osteoporosis International, August 2006). An earlier study from Sweden showed that men who were highly competitive soccer players in their youth and then gave up active sports did not have bigger and stronger bones and did not have fewer fractures than people who never exercised at all. On the other hand, people who did not exercise in their youth, but started and continued their exercise programs into later life did have larger and stronger bones.

A person has the strongest bones at ages 20 to 30. After that people lose bone continuously for the rest of their lives. Any activity helps keep bones strong, but exercises that put extra pressure on specific bones offer greater benefit. That is why weightlifting is a much better exercise for strengthening bones than swimming. The bones in the arm that hold the racquet in tennis players are much stronger than the other arm. Pick any sport that keeps you active and try to do it daily for the rest of your life. Take off only when you are tired or sick or your muscles are sore.


Dear Dr. Mirkin: Will taking longer steps help me run faster?

You cannot run faster by consciously trying to increase your stride length. When you try to take longer strides that feel unnatural, you lose energy and run more slowly. Your most efficient stride length is determined by what feels most comfortable to you. Your heel hits the ground with great force. The tendons in your legs absorb some of this energy and then contract forcibly after your heel hits the ground so you regain about 60 to 75 percent of that stored energy. When you try to take a stride that is longer than your natural one, you lose a great deal of this stored energy, tire much earlier and move your legs at a slower rate.

When most athletes run as fast as they can, they run at close to the same stride rate. For example, a video at the New York City Marathon showed that the top 150 runners had the same cadence, taking 92 to 94 steps a minute. The difference between the top runners and the others is that the best runners took longer strides. The key to running faster in races is to make your leg muscles stronger so you can contract them with greater force so they drive you forward with a longer stride. Competitive runners strengthen their legs by running very fast in practice two or three times a week and by running up and down hills once or twice a week.


Recipe of the Week

It’s time to make a batch of my favorite holiday treat:
Fruity Pebbles

You'll find lots of recipes and helpful tips in
The Good Food Book - it's FREE

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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