Marathon running appears to cause heart damage.  12% of asymptomatic marathon runners had evidence of myocardial damage.  Only 4% of the sedentary controls had damage.<p>This Breuckmann study repeatedly found about a 2.5 to 1 increased incidence of heart attack from marathon running over sedentarism.  The number of marathons run was an independent and significant predictor of the likelihood of myocardial damage.<p><a href="http://www.paleonu.com/panu-weblog/2009/11/1/cardio-causes-heart-disease.html" rel="nofollow">http://www.paleonu.com/panu-weblog/2009/11/1/cardio-causes-h...</a>