Long-distance runners double "dilating" capacity of their coronary arteries

Long-distance runners have a greater capacity to "dilate" their coronary arteries and thus markedly increase blood flow to their heart muscle, according to the preliminary findings of California exercise researchers.

"This study is unique in that it provides the first evidence in living humans that prolonged endurance training may substantially affect coronary artery anatomy and physiology," says an editorial accompanying the new study. The research report and editorial are published in the American Heart Association's scientific journal Circulation.

Eleven men who underwent vigorous aerobic exercise training demonstrated a dilating capacity of their coronary arteries that was about twice as great as that of a group of 11 sedentary men, reports William L. Haskell, Ph.D., lead author of the study and professor of medicine at Stanford University School of Medicine, Palo Alto, Calif.

The 11 middle-aged runners in the study trained about 50 miles per week for an average of 13 years and during the past two years had participated in "ultradistance" running. All 11 had run the Western States 100-Mile Trail Run, an ultramarathon race from Squaw Valley, Calif. to Auburn, Calif. over some mountain trails, the scientists say. Among the group of 11, their average best time for running a 100-mile race was 19 hours and 55 minutes.

What about lesser mortals who run for only 30 to 60 minutes, at least three times a week, as the AHA recommends? Will that level of exercise improve the coronary arteries' dilating capacity?

"We don't know how much of a change in coronary artery dilating capacity is achievable with lower levels of exercise," says Haskell, an exercise physiologist. "So this study is really just a first step."

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