Chronic Long-Distance Training May Harm the Heart;
Can Too Much Exercise Be Harmful? Chronic Long-Distance Training May Harm the Heart; Moderate Running Linked With Lower Death Risk, Studies Find June 4, 2012 -- Exercisers who train chronically to compete in marathons, triathlons, and other long-distance events may be hurting their heart health, according to a new report. "Chronic extreme endurance efforts, like marathons, ult..