@B, Perhaps, to an extent, it depends on what you consider "fringe". The "Cardio Causes Heart Disease" blog entry seems pretty "fringe" to me, but perhaps it isn't to some others.
The concept that vigorous physical exertion increases the short-term risk of sudden cardiac death isn't surprising, new, or unsubstantiated elsewhere in the medical literature. The presentation of additional data to this, or similar, effect doesn't strike me as "fringe".
What makes it "fringe" to me is that it is the thoughts of a neuroradiologist posted on a personal blog, and the thrust of the blog entry seems to be that this article offers greater support for a number of other premises outside of the scope of the article. By presenting these thoughts on a blog, it strikes me as more of a personal thought process, rather than a formal medical opinion. Perhaps if his thoughts were more fully refined, he would present such an argument is in a journal, to allow for a bit more thorough scrutiny. If it matters, I cannot find any record of him previously publishing any thoughts on cardiac disease in the past.
"Fringe" doesn't mean that his comments are invalid or unworthy of consideration-- he could be entirely right. I do find it noteworthy that he doesn't mention that in the same journal issue an article entitled "Is Marathon Running Hazardous
to Your Cardiovascular Health?
The Jury Is Still Out" was presented. Lastly the choice of blog entry title strikes me as a very far-reaching conclusion based on a study of about 100 German men, all over the age of 50, with an average age of 57, who ran at least 5 marathons over a 3 year period.