Is marathon running bad for your heart? Sigh...

I spotted a news story on the BBC News website this morning which claims that Marathon training 'may pose a heart risk'. This story has since caused a bit of a buzz on the interwebs, cropping up in various tabloids and on various discussion forums and blogs. Being a runner and a scientist, this of course piqued my interest. Is this something that I should be concerned about, or is this another case of sensationalism by the media? Take a guess...

First things first. The study in question is a paper published yesterday (6th December 2011) in the European Heart Journal by a group in Belgium entitled  "Exercise-induced right ventricular dysfunction and structural remodelling in endurance athletes". Unfortunately, it requires a subscription, but you can see the abstract here. Being a scientist myself, I have looked over the paper and thought that I would share my thoughts on the implications.

The study measures various aspects of cardiac function for 40 endurance athletes, each a specialist in one of 4 events which are, in order of duration; marathon, endurance triathlon (possibly Olympic length?), alpine cycling, or ultra-triathlon (Ironman distance). Measurements of cardiac function were taken using cardiac magnetic resonance imaging (cMRI) and echocardiograms, as well as analysis of biochemical markers of function such as B-type natriuretic peptide (BNP) and cardiac troponin I (cTnI), both proteins involved with contractions of muscle cells in the heart and hence good predictors of cardiac risk. For each athlete, three measurements were taken; the first was taken as a baseline 2-3 weeks prior to the event, the second was taken within an hour of crossing the finishing line at the event, and the final 'delayed' measurement was taken 6-11 days after the event.

Broadly speaking, they found the following key results: