Jogging is it harmful or great according to this article by WebMD it all depends on your state of health.

Exercise that raisesheart rates clearly lowers the risk ofstroke and heart attack. But what about those reports of joggers who die suddenly while trying to do their body good? Danish researchers have shown that joggers who stick with it have a lower risk of death than non-joggers or those who throw in the towel, according to a report in the Sept. 9 issue of the British Medical Journal. Butdoctors do urge caution for joggers who are inactive or overweight or who haveheart disease or diabetes.

"Many studies have shown that physical activity has a positive effect on health, but the optimum frequency, intensity, and duration of exercise haven't yet been established," says lead author (and jogger) Peter Schnohr, MD, chief cardiologist of the Copenhagen City Heart Study. "Still, vigorous exercise like jogging is thought to be most beneficial."

Due to the public concern about deaths during jogging, researchers followed over 4,600 Danish men from 20 to 79 years of age for 10 years. Along with their medical and smoking history, participants were polled about jogging.After accounting for high blood pressure, high cholesterol, and other risk factors for heart disease, death rates were significantly lower among regular joggers than non-joggers or those who fell out of the habit.

In fact, the American College of Sports Medicine recommends moderate aerobic exercise for 30-50 minutes three times a week or more. "But that doesn't mean you should cram it all in between Friday and Sunday," says exercise physiologist Jim Hagberg, PhD, a professor of kinesiology at the University of Maryland, in Baltimore. "Because there's not any training adaptation, weekend warriors are putting themselves at risk, especially if they've got high blood pressure."

Even well-trained athletes can run into problems, but it's much rarer. In July, a 38-year-old man died of an irregular heartbeat during Atlanta's Peachtree Road Race, a popular 10 kilometer event. It was later found that he had significant --- but undiagnosed -- heart disease.

"Cases like this tend to stay on our minds, but more people die [this type of death] when resting at home than they do during exercise," says cardiologist and veteran marathon runner Paul Robinson, MD, a 67-year-old associate professor of medicine at Atlanta's Emory University. "For most joggers, the benefit of chronic disease prevention far outweighs any risk of sudden death."

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