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Increase Endurance with Carbohydrates

A study from The University of Bern in Switzerland shows that a high carbohydrate, high-fat diet for three days before competition can help athletes store more fat in their muscles and use much more muscle fat for energy during exercise (European Journal of Applied Physiology, November, 2006). Endurance-trained athletes exercised for three hours to empty sugar and fat reserves from their muscles. Then they ate a high-carbohydrate, low-fat diet for 2.5 days or the same diet with lots of added fat for the last 1.5 days. Athletes who ate the high-carbohydrate, high-fat diet stored 55 percent more fat in their muscles and used more than three times as much of that fat during exercise.

The data on fat storage may have no practical value for endurance athletes because the authors were not able to show that the extra fat stored in muscles increased endurance. This is probably because there is almost an unlimited amount of energy available from a person’s own body fat. Changing the percentage of fat use from body fat to muscle fat would not increase energy sources and therefore would not increase endurance.

Carbohydrates are another story. Normally there is only a small amount of carbohydrates stored in the muscles, liver and bloodstream. Storing extra carbohydrates in muscles is beneficial because when a person runs out of stored muscle sugar, his muscles hurt and are more difficult to control. In the 1940s, Per Olaf Ostrand showed that a high carbohydrate diet for several days before athletic competitions helps a person store more sugar in muscles, which does increase endurance. Since then athletes have eaten high-carbohydrate diets before competition and often have pre-race pasta parties. Subsequent studies showed that highly-conditioned endurance-trained athletes can maximally fill their muscles with sugar just by eating their usual meals and cutting back on their heavy workloads for a few days before competition.


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Dear Dr. Mirkin: Why do foods such as prunes prevent constipation?

At last, scientists at the Medical College of Georgia have explained why high-fiber foods keep you regular (PloS Biology, September 2006). Rough and bulky foods brush against the inner linings of your intestinal tract and break the membranes that surround each cell. Immediately, calcium in the outside fluid moves inside the cell to signal mucous-filled compartments inside the cell to come together and form a patch to heal the breaks in the surface membranes. The cells release mucous to keep bulky stool moving along your intestinal tract. Cells lining your intestinal tract live only around 48 hours anyway, so this damage is not harmful as long as you don’t also take a lot of aspirin or alcohol which cause even more damage. If you suffer from irregularity, eat more whole grains and vegetables and drink lots of fluids. More on constipation:


Dear Dr. Mirkin: My calves hurt when I walk. Should I exercise?

If your legs don't hurt at rest and you develop pain in your calves after walking for a short time, you may have intermittent claudication, a partial obstruction of the blood flow to your legs. When you walk, your leg muscles require a large amount of blood and a partial obstruction of the arteries carrying blood to your legs can prevent extra blood from getting through, causing your calf muscles to hurt. Several weeks exercise program can triple the distance you can walk without pain, but people with intermittent claudication have blocked arteries in other areas, so check with your doctor. You need to find out why your arteries are blocked, and you may need a supervised exercise program.

A study from Australia shows that a regular program of walking, but not cycling, can markedly prolong the distances patients with intermittent claudication can walk before they develop pain (Journal of Vascular Surgery, July 2006). This study shows that training is specific. World-class triathletes who compete in swimming, running and cycling are never world-class in any of these sports. You use your leg muscles much differently in walking, running and cycling. Running and walking stress primarily the muscles in your lower legs, while cycling stresses primarily the muscle in your upper legs. If you want to be the best you can be in any sport, spend your time training in that sport, rather than cross-training.


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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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