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Intervals Teach Your Muscles to Use Lactic Acid

You exercise so intensely that your muscles burn and you gasp for breath. Then you slow down for a minute or two, catch your breath, and then go very fast again. This training technique has been used in all endurance sports since the 1920's. Now George Brooks of the University of California at Berkeley has shown why interval training makes you a better athlete (American Journal of Physiology-Endocrinology and Metabolism, June 2006).

Inside each muscle cell are mitochondria, the little furnaces that burn fuel for energy. A major fuel for your muscles during exercise is the sugar, glucose. In a series of chemical reactions, glucose is broken down step by step, with each step releasing energy. When enough oxygen is available, the glucose releases all of its energy until only carbon dioxide and water remain; these are blown off through your lungs. However, if not enough oxygen is available, the chemical reactions stop at lactic acid which accumulates in the muscles and spills over into the bloodstream. Lactic acid makes muscles acidic and causes a burning feeling. This recent research shows that lactic acid is the most efficient source of energy for muscles. Anything that helps muscles to break down lactic acid faster will make you a better athlete because it will increase your endurance and allow you to move faster when you are tired.

Since lactic acid is burned for energy in the mitochondria, anything that enlarges the mitochondria builds a bigger furnace and helps to increase endurance. Lactic acid is carried from the cells into the mitochondria by special proteins called lactate transporter molecules, so anything that increases these molecules will build endurance. An enzyme called lactic acid dehydrogenase is needed to start the reaction, so anything that increases this enzyme will also help. Interval training does all three: it enlarges the furnace (mitochondria), increases lactic acid transporter molecules, and increases the amount of lactic acid dehydrogenase.


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Dear Dr. Mirkin: Does having Metabolic Syndrome mean I should avoid all fats?

Metabolic syndrome, or syndrome X, means you have any three of the following: abdominal obesity, high triglycerides, low HDL cholesterol, high blood sugar or high blood pressure. Researchers in Brussels, Belgium found that people who suffer from the metabolic syndrome should increase their intake of omega-3 fatty acids found in seafood, seeds and many vegetables. (American Journal of Clinical Nutrition, June 2006).

Omega-3 fatty acids help to reduce the amount of fat in the liver and muscles. Excess fat in the liver prevents the liver from removing insulin from your bloodstream, causing high blood insulin levels and leading to diabetes. Omega-3 fatty acids lower blood levels of triglycerides, and lowering triglycerides raises blood levels of the good HDL cholesterol. Omega-3s also lower the fraction of heart attack causing small, dense LDL cholesterol. They also reduce inflammation and clotting, widen arteries and lower high blood pressure. That’s why most doctors recommend a Mediterranean type of diet that includes plenty of fish, vegetables, beans, nuts and other seeds.


Dear Dr. Mirkin: Does exercise strengthen bones?

When you strengthen your muscles, you also strengthen your bones. If you’re not exercising, regardless of your age, you are setting your bones up for osteoporosis. A study from Deakin University in Melbourne, Australia shows that lifetime sports and leisure activity participation is associated with greater bone size, quality and strength in older men. The older men who exercised regularly when they were younger have stronger, bigger and tougher bones that are harder to break. (Osteoporosis International, June 2006).

Weight-bearing exercise in early life helps strengthen bones for later life, and exercising to strengthen muscles also strengthens the bones on which these same muscles attach. Another study showed that professional tennis players’ bones in the arm that holds the racquet are much larger and stronger than the bones in the other arm. The arm bones are bigger, denser and stronger in athletes who whose activities involve upper body strength, such as rugby, rock climbing, kayaking, and weight lifting, while leg bone mineral density was highest in athletes whose activities included both running and strength training.


More Ready-to-Eat Whole Grains

Many of you wrote to tell me about Uncle Ben’s cooked brown rice, apparently available in many supermarkets. Try the ready- to-eat whole grains, or cook your own, for . . .

Spanish Rice (good hot, at room temperature or chilled)

You'll find lots of whole grain recipes, cooking instructions, helpful diet tips and more in The Good Food Book - it's FREE

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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