Runners can reduce their mileage and still maintain their racing sharpness


August 31, 1993|By Dr. Gabe Mirkin | Dr. Gabe Mirkin,Contributing Writer/United Feature Syndicate

All runners reach a period when they need to back off from hard training. Even if they are still in racing season, they can cut back on their mileage as long as they continue to run very fast some of the time.

Most runners are afraid to reduce their mileage because they know it takes years to reach a high level of fitness and they don't want to lose what they've worked so hard to attain. When runners take several days off, they lose fitness. Marathon runners who take three weeks off lose 7 percent of their racing sharpness. That translates into 11 minutes for a 3-hour &r marathoner.

It takes years to increase the levels of muscle chemicals that process oxygen and sugar. But in just three weeks of rest, these enzyme levels drop significantly and blood volume drops as much as 10 percent. Reduced blood volume decreases the amount of blood that supplies oxygen to the muscles.

One study showed that running slow for just a few weeks markedly slows race times. However, running fewer miles will not slow race times if you run very fast in practice. If you reduce the amount of miles that you run by two-thirds and still run fast, you can maintain race speed for up to 10 weeks. To maintain your competitive edge, you must run fast, even if you run fewer miles.

Should I be taking vitamin E to prevent heart attacks?

A recent report from Harvard showed that women who took more than 100 international units of vitamin E supplements had a 40 percent lower incidence of heart attacks (New England Journal of Medicine, May 20, 1993). Vitamin E is an antioxidant that helps to prevent the bad LDL cholesterol from being converted to oxidized LDL, which causes plaques to form in arteries.

The authors did an excellent job of removing other confounding factors from the study. For example, people who take vitamin E supplements could have been less likely to smoke, a habit that causes heart attacks. The study showed that smokers who take vitamin E pills were also less likely to suffer heart attacks than other smokers. The data also showed that people who took vitamin E for fewer than two years and those who took less than 400 international units per day were not less likely to get heart attacks. There was no additional benefit from taking more than ++ 400 international units. When you try to eat less fat, you avoid the rich fat sources of vitamin E, such as vegetable oils, egg yolks, milk fat, butter, liver and nuts. If you plan to be on a low-fat diet and still get enough vitamin E from the foods that you eat, you should eat lots of other sources of vitamin E, such as vegetables and cereals.

My 9-year-old son wants to lift weights with me, but my wife thinks he could hurt himself. Should children do weight lifting?

Young children can become very strong by lifting weights and they are not more likely than adults to injure themselves.

Children can be protected from injury by being supervised by experienced lifters. They should do only two-handed barbell exercises, rather than using single-handed dumbbells. They should never lift a weight that is heavier than they can lift 10 times in a row, and they should stop lifting immediately when they start to hurt or lose their form.

There are two ways to become stronger: One is to make your muscles larger, and the other is to simultaneously contract a greater percent age of the fibers in a muscle. Weight lifting does not make young children's muscles very large. Instead, it develops their ability to contract a greater percentage of their fibers together.

Muscles are made up of thousands of individual fibers. When you lift a heavy weight, you contract only around 3 percent to 5 percent of your muscle fibers at the same time.

Lifting weights does not affect a child's growth rate. Bones grow only from the growth centers, which are located near their ends and are weaker than normal bone. These centers solidify and become as strong as bone when a person stops growing.

EDr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.

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