Evan and Rob are runners of equal ability. Evan runs 100 miles a week at a fairly quick pace, but he doesn't do any special speed training. Rob runs 50 miles a week, but he runs very fast twice a week.
Rob will run a faster marathon, because running short distances very fast during practice will help the racer cover a longer distance in less time.
A runner slows down near the end of a marathon because of a build-up of lactic acid in the muscles. Lactic acid begins to break down as soon as it is exposed to oxygen. Anything that increases a runner's ability to break down lactic acid at a faster rate will help improve endurance.
study from the University of North Carolina-Greensboro has demonstrated that very fast running can break down lactic acid in the muscles -- even if it does not increase an individual's maximal ability to take in and use oxygen. While slower training markedly increases a runner's maximal ability to take in and use oxygen, it does not clear lactic acid as rapidly as faster running can. The difference is that slower running does not improve the ability of muscle fibers to break down lactic acid the way faster running does.
Good marathon runners have to run fast intervals at least twice a week. They should run a very short distance very quickly, rest by running at a slower pace and then run very fast again. A good routine is to run a 1/4 -mile 12 times, averaging less than a minute each, with 70-second rests between each fast spurt.
Simply stated, you can't run a very fast marathon without interval, or speed, training.
Q: My neighbor had a heart attack last year and walks every day for exercise. His doctor told him to cover his face when he's out in cold weather. Why?
A: All people who have heart disease should protect their faces from cold winds and rain. The cold can chill their faces and cause chest pain. It can even cause a heart attack.
Your heart muscle needs oxygen to pump blood throughout your body. The heart gets its own oxygen from the blood that is pumped to it through the vessels on its outside surface.
Even if fatty plaques, a symptom of heart disease, collect in the inner lining of the arteries leading to the heart, the heart may still get enough oxygen -- when your body is at rest. But when you exert yourself, your heart has to work even harder. You may develop chest pain because your heart is not able to get all the oxygen it needs.
When your face is cold, your heart beats at a much slower rate. As a result, the heart muscle may not get enough oxygen and you, in turn, develop chest pain.
Individuals with heart disease should cover their faces when they go out in cold weather. They may choose to wear hooded caps that cover the chin and forehead or they can raise their coat collars and wear scarves over their faces.
Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.