<a href="http://eurheartj.oxfordjournals.org/cgi/content/full/29/15/1903" rel="nofollow">http://eurheartj.oxfordjournals.org/cgi/content/full/29/15/1...</a><p>"The more marathons run, the higher the likelihood of heart disease. The number of marathons run was an independent and significant predictor of the likelihood of myocardial damage.<p>The runners had about the same prevalence of non-zero coronary calcium compared to age matched controls randomly assigned from a survey population."