World records in running are getting faster, and studies conducted at the University of Missouri at Columbia show why.
Thirty years ago, a top marathon runner would train with a workout of 40 quarter-mile runs, averaging 67 seconds each. Today, no knowledgeable marathoner would run that many quarter-mile repeats that slowly. They know that to run fast in competition, you need to run fast in practice. A more respectable workout would include only 12 quarters, run much faster and averaging fewer than 60 seconds each.
At the annual meeting of the American College of Sports Medicine, Dr. Ben Londeree explained why running fewer, faster intervals helps runners run more quickly in races.
Muscles are made up of white strength-and-speed fibers and red endurance fibers. The white fibers are further classified into type A, which use oxygen effectively, and the fast-twitch type B, which do not.
During very fast endurance running, most of the lactic acid that builds up in muscles comes from the fast-twitch type-B fibers. A buildup of lactic acid in muscles causes fatigue. But setting up a program in which you run progressively faster in practice once or twice a week will help you increase your time in a race. By running fast enough that you get into severe oxygen debt will cause the fast-twitch type-B fibers to convert into A fibers, which do not produce as much lactic acid. Therefore, your muscles won't become as fatigued and you'll be able to keep up your speed.
Q: My daughter has exercise-induced asthma and uses special medication to control it. She wants to try out for the school swim team. Will swimming trigger her asthma? Will her medication give her an edge?
A: Although most of them don't know it, 10 percent of all Americans suffer from exercise-induced asthma. They occasionally become short of breath 5 to 12 minutes after they
start to exercise.
When some people breathe rapidly and deeply during exercise, their bronchial tubes produce copious amounts of mucus, causing them to have difficulty moving air around the mucus. These people have exercise-induced asthma. It is most likely to occur when they breathe cool, dry air; running is a frequent cause. Breathing moist, warm air, on the other hand, rarely triggers an asthma attack. So swimming is the sport least likely to cause exercise-induced asthma.
Most asthma attacks can be prevented by using a special inhaler containing potent stimulants called beta 2 agonists. However, recent studies show that the stimulants in these inhalers do not give an asthma sufferer an unfair advantage over other athletes. Athletes with asthma are permitted to use the inhalers even in Olympic competition.
Q: Should I be worried about too much fat in my child's diet?
A: A panel of experts appointed by the National Heart, Lung andBlood Institute has recommended that children over the age of 2 follow the same low-fat, low-cholesterol diet recommended for adults -- less than 30 percent of calories from fat, less than 10 percent of calories from saturated fat and fewer than 300 milligrams of cholesterol each day.
These recommendations are very controversial, though.
First, there is no evidence that this minimal reduction in fat intake will significantly lower blood cholesterol.
Also, there are no data to show that a low-fat diet in childhood will prevent heart disease in adults.
Furthermore, 30 percent of girls and 50 percent of boys who have high cholesterol as children do not have high cholesterol as adults.
And, finally, fat restriction in childhood is associated with being smaller as an adult. The time to start restricting food and fat is after an individual stops growing.
Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.