This sounded like a warning, but Wannamethee and Shaper continued working on their data, and in 1994 reported that all the deaths in the highly active men were in a sub group with high blood pressure. The risk of heart attack for men with high blood pressure was twice as high for vigorously active men compared to moderately active men. But there was no increase in risk for the most active men compared to moderately active men in the normal blood pressure subgroup. Summing up, there is no reliable and consistent evidence that the health benefits of moderate physical activities begin to head downhill if you step up to vigorous levels, as long as your blood pressure is normal. In a new study, in which Blair is collaborating with other laboratories, a comparison between runners consistently logging more than 40 miles a week, and those completing 20 to 40 miles a week, so far has found no increase in cancer and heart disease in the highest mileage group.
Some people die during vigorous activity.
But heart attacks triggered by heavy exertion are more likely in people who are normally sedentary, according to studies led by Murray Mittleman, M.D.C.M., M.P.H., at Harvard Medical School, and by Stefan Willich, M.D., M.P.H., at Free University of Berlin, Germany. The incidence of sudden death is very small, one death per 7,620 joggers, says a review from Paul Thompson, M.D., and colleagues at the Miriam Hospital in Providence, Rhode Island. But if you are going to have a heart attack, you are more likely to have it during or shortly after working out. However, this doesn't change the fact that moderate and vigorous exercise reduces risk of heart disease in healthy folks. A small part of the oxygen you breath in is converted to very active compounds called free radicals.