Don't run over 30 miles per week, that's the new advice.
... mounting evidence that extraordinary doses of exercise may diminish the benefits of modest amounts,... That extra six years of longevity running has been shown to confer? That benefit may disappear beyond 30 miles of running a week, suggest recent research.
The improved blood pressure, cholesterol levels and robust cardiac health that exercise has been proven to bestow? Among extreme exercisers, those blessings may be offset partially by an increased vulnerability to atrial fibrillation and coronary-artery plaque, suggest other recent studies.