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How Sugar During Exercise Makes You Faster and Stronger

Just about everyone agrees that taking carbohydrates, particularly sugar, during exercise increases endurance in both humans and animals. For years, I have told everyone that eating sugar preserves stored muscle sugar called glycogen. However we have to find a new explanation because recent data show that taking sugar during exercise does not preserve muscle glycogen (Sports Medicine, September 2010). The NEW most likely explanation is that during prolonged, intense exercise, you become exhausted because you cannot keep up with your requirements for oxygen. This interferes with the sodium/potassium pumps, inside cell membranes, that pump potassium into cells and sodium out of cells.

Your brain sends electrical messages along nerves to tell your muscles to contract. When the electrical message that travels along nerves reaches its connection with muscles, other electrical messages travel along muscles to cause them to contract. The electricity comes from your cells' ability to keep sodium outside cells and potassium inside cells. This is done by "pumps" in the cell membranes.

During intense exercise, how fast you can move is limited by how long it takes to get oxygen into muscles. Anything that reduces your requirements for oxygen will help you to move faster. Sugar and other carbohydrates require less oxygen than fat and protein to supply energy to your "pumps", so sugar is a very efficient source of energy for the sodium/potassium pumps during exercise. When the sodium/potassium pumps lose their efficiency from lack of oxygen, potassium leaks from cells and you can't get enough electrical current to contract your muscles with the force you need to compete. So your muscles weaken and you have to slow down.

If you want to compete in sports that last more than 45 minutes, you will probably be faster and have greater endurance if you take in sugar while you exercise. Taking caffeine with sugar during prolonged exercise increases endurance even more. We drink sugared, caffeinated soft drinks when we race, and avoid them when we are not racing. When muscles contract, they remove sugar so rapidly from the bloodstream that you do not get a high rise in blood sugar. However when muscles are not contracting, you lose this benefit and can develop a high rise in blood sugar that can damage all of the cells in your body.


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Dear Dr. Mirkin: If vigorous exercise is good for you, why have so many former world-class athletes died of heart attacks?

The most likely cause is previous use of anabolic steroids and human growth hormone (HGH). Doctors at the Massachusetts General Hospital found that apparently healthy, older former long- term users of anabolic steroids have weaker left ventricles, the major pumping chamber of the heart. This markedly increases their risk for heart failure and heart attacks (Circulation: Heart Failure, July 2010).

Many world class athletes in sports requiring extreme strength took anabolic steroids from the early 1960s on. When these athletes were in competition, their training made their hearts stronger than those of other people their age, and available tests failed to show any heart muscle damage. With aging, the hearts of all people weaken because they lose muscle fibers. As these former users of anabolic steroids reach middle and older age, tests can detect the heart muscle weakening that increases their risk for sudden death from heart attacks.

Taking large amounts of HGH can cause sudden death from irregular heart beats. HGH causes heart muscle to grow far more than its nerves do, and everyone loses nerves with aging. The effect of former HGH use on the hearts of older athletes has not been documented, but we do know that people who have acromegaly, a brain tumor that produces large amounts of HGH, are at increased risk for sudden death from irregular heart beats.


Dear Dr. Mirkin: Does stretching help to prevent injuries?

There's no good evidence that stretching prevents injuries. A USA Track & Field-sponsored study involving 3,000 runners showed no difference in injury rate between those who stretched before running and those who did not ( USATF, published online August 23, 2010 ). They also found that similar injury rates occurred in women and men, runners performing high and low mileage, runners who were flexible or inflexible, high and low level runners, and those who were younger or older.

On the other hand, increased risk for injury occurred in heavier runners and those who had previously been injured. Increased risk occurred also in runners who had previously stretched and stopped stretching because they were put into a non-stretching group. The study's author, Dr. Alan Roth, recommends that runners who are already stretching should continue to stretch.


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June 21st, 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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