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Low Blood Sugar Causes Mental Fatigue During Competition

Athletes can expect to feel fatigued when their blood sugar levels drop. Researchers at Loughborough University, UK showed that athletes who did not take sugar during soccer competition lasting 90 minutes felt more tired, had less competitive desire, and had far lower blood sugar levels than athletes who took a sugared drink every 15 minutes during their game (Scandinavian Journal of Medicine & Science in Sports, October 2007).

Your brain gets more than 98 percent of its energy from sugar in the bloodstream. However there is only enough sugar in the bloodstream to last about three minutes. The liver must constantly release sugar into the bloodstream, but there is only enough sugar in the liver to last eight hours during rest and far less than that during exercise. So athletes who do not take a source of sugar during events lasting more than an hour can suffer the psychological effects of low blood sugar levels what include a mental feeling of fatigue and lowered competitive desire.

In another study, researchers at the University of Waterloo in Canada showed that taking sugar 30 minutes after starting to cycle and every 15 minutes afterwards increases strength, speed and endurance when exercising fairly intensely at 60 percent of maximal oxygen uptake (Journal of Applied Physiology, July 2007). Muscles burn carbohydrates, fats, and protein for energy. Carbohydrates (sugars) require the least amount of oxygen for conversion to energy, which allows you to move faster with less effort. Athletes use sugared drinks, power bars or candy bars, concentrated sugared gels, cookies and almost any other source of carbohydrates during prolonged competition. It is possible to take in too much sugar and get a high rise in blood sugar if you are not exercising intensely, but this is rarely a concern for competing athletes. Competition takes great concentration, and eating and drinking are distractions that most athletes limit as much as possible.


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Dear Dr. Mirkin: Why do so many of my swim team members use asthma inhalers?

Swimming may attract a larger number of asthmatics than other sports because the moist atmosphere created by the pool helps them to breathe comfortably and avoid asthma attacks. However, many swimmers who do not have asthma use the inhalers to give them a competitive advantage. At the Olympic Games in Sydney, Australia in 2000, 607 out of 10,300 competitors (approximately six percent) filed notifications that they needed to take beta-2 agonist asthma inhalers to prevent exercise-induced asthma.

Beta-2 agonists such as albuterol, salbutamol, salmeterol and terbutaline open the closed lungs of asthmatics and help them to breathe. They also increase the amount of fat in the bloodstream to increase energy sources of exercising muscles, help to preserve the muscles' store of sugar, and help muscles to contract with more force. Researchers from Orléans, France decided to test the effects of salbutamol inhalation on an athlete's endurance (British Journal of Sports Medicine, July 2007). They showed that inhaling salbutamol prior to competition made the athletes faster in endurance events and gave them greater muscle strength.


Dear Dr. Mirkin: Does coffee help or hurt the heart?

Some studies show that coffee increases risk for heart attacks, while others claim that it helps to prevent them. A report from the University of Toronto and Harvard School of Public Health suggests that this dilemma is caused by genetic differences in the way people metabolize caffeine (Current Opinion in Clinical Nutrition & Metabolic Care, November 2007). Coffee is a complex mixture of compounds that may be either beneficial or harmful. Previous studies have confirmed a cholesterol-raising effect from the diterpenes present in boiled coffee, which may contribute to the risk of coronary heart disease. However, several studies show that moderate coffee consumption is associated with reduced risk for heart attacks. Dipterines are removed by filtering, and other antioxidants that remain in filtered coffee may be protective. Most coffee consumed in North America is filtered.


Recipe of the Week

Easy Split Pea Soup

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June 25th, 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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