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What Is Second Wind?

You are running at a brisk pace that makes you very short of breath and your muscles start to burn. After a while you feel better and pick up the pace. It's called the "second wind", but it really is caused by a combination of:
• slowing down, and
• using lactic acid as a major fuel for your muscles.

HOW MUSCLES GET THEIR ENERGY: Your muscles use carbohydrates, fats and proteins for energy. More than 80 percent of the energy used to power muscles is lost as heat, so burning fuel instantly for energy would produce so much heat that it would burn and destroy your muscles. Your muscles convert food to energy in a sequence of chemical reactions with each chemical reaction providing a little energy and a little heat. The main source of fuel for your muscles during exercise is called the Krebs Cycle and is located in the mitochondria, small chambers inside every cell in your body except red blood cells.

WHY MUSCLES BURN WHEN YOU RUN VERY FAST: Each chemical reaction is started by a different enzyme. Enzymes in muscles break down food in a series of reactions that release small amounts of energy at a time. Enzymes require oxygen to turn food into energy. When you exercise so hard that you can't get all the oxygen you need to break down food for energy, the reactions stop at a point where lactic acid accumulates in muscles and spills over into the bloodstream. This makes muscles acidic and it is the acidity that makes muscles burn and forces you to slow down.

HOW LACTIC ACID CAUSES SECOND WIND: The limiting factor to how fast you can run is the time it takes to move oxygen into your muscles. Muscles require less oxygen to turn lactic acid into energy compared to the amount of oxygen required to to use carbohydrates, fats or proteins (Sports Medicine, June 2006;36). So lactic acid is the most efficient fuel for muscles since it requires less oxygen even than sugar. When you exercise as hard as you can, lactic acid helps you to go harder. When muscles produce lots of lactic acid, they use this chemical for energy which requires less oxygen. As soon as you slow down, you catch up on your oxygen debt and recover. So lactic acid is good for you. It helps you to exercise with less available oxygen and helps you to move faster.


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Most Sore Throats Do Not Need Antibiotics

The Infectious Diseases Society of America issued new guidelines stating that most throat infections are caused by viruses and therefore should not be treated with antibiotics (Clinical Infectious Diseases, published online September 9, 2012). Almost 70 percent of North Americans with a sore throat receive antibiotics, even though bacteria are found in only about 15 percent of children and 10 percent of adults.

SYMPTOMS THAT INCREASE RISK FOR HAVING A STREP INFECTION: A sore throat is more likely to be caused by group A strep if there is:
• sudden onset of pain,
• pain on swallowing, and
• fever.

All viral infections can cause:
• coughing,
• running nose,
• hoarseness, and
• mouth ulcers.

WHO NEEDS A CULTURE? Children from age three to 18 are at increased risk for rheumatic fever and heart and kidney damage from beta strep, group A infections. They should get a throat swab for a rapid antigen test or culture. Children younger than three years and adults are far less likely to have a strep throat.

TREATMENT: The treatment of beta strep infections is a 10-day course of penicillin, amoxicillin or a cephalosporin. People allergic to penicillin can take erythromycin-type drugs such as azithromycin. (New England Journal of Medicine, Feb 17, 2011).

WHY TAKE ANTIBIOTICS FOR A STEP THROAT? Antibiotic treatment reduces risk for rheumatic fever, ear infections, and tonsil abscesses caused by strep and other bacteria.

WHY YOU SHOULD NOT TAKE ANTIBIOTICS UNLESS IT IS A BACTERIAL INFECTION: Antibiotics increase the number of bacteria that are resistant to that antibiotic. Also, your immunity depends on the types and numbers of many different bacteria in your body. Taking antibiotics decreases the diversity of bacteria in your body to decrease your immunity.


Antibacterial Ingredient May Harm Muscles

Triclosan, an antibacterial chemical found in many soaps, creams, deodorants, mouthwashes, toothpaste, bedding, clothes, carpets, toys and trash bags, weakens muscle contractions in mice and slows swimming fish (Proceedings of the National Academy of Sciences of the United States of America, September 2012). Other studies have shown that triclosan can prevent animals from becoming pregnant.

Triclosan, in doses similar to what humans receive from using soap containing the chemical, reduced the force of heart and skeletal muscle contractions. In mice, a single dose of triclosan caused a 25 percent reduction in heart muscle force and an 18 percent reduction in grip strength.

We do not yet have any studies showing that triclosan causes muscle damage in humans, but there are other concerns about this common chemical and the FDA is currently reviewing its safety; see FDA Consumer Update: Triclosan


Recipe of the Week:

Sweet Potato Curry

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


September 23rd, 2012
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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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