Editing Marathon (section)

===Cardiac health===
[[File:VVM 2007 foto 0284.JPG|thumb|Officers patrolling a marathon course in [[Ukraine]]]]
In 2016, a systematic medical review found that the risk of [[Sudden cardiac death of athletes|sudden cardiac death]] during or immediately after a marathon was between 0.6 and 1.9 deaths per 100,000 participants, varying across the specific studies and the methods used, and not controlling for age or gender.<ref>{{cite journal |journal=The Physician and Sportsmedicine |volume=44 |issue=1 |date=January 2016 |title=Sudden cardiac death in marathons: a systematic review |vauthors=Waite O, Smith A, Madge L, Spring H, Noret N |pages=79–84 |doi=10.1080/00913847.2016.1135036 |pmid=26765272 |s2cid=36458482 |url=http://ray.yorksj.ac.uk/id/eprint/1282/1/Waite%20et%20al%202016.pdf |access-date=19 March 2018 |archive-url=https://web.archive.org/web/20170921225307/https://ray.yorksj.ac.uk/id/eprint/1282/1/Waite%20et%20al%202016.pdf |archive-date=21 September 2017 |url-status=live}}</ref> Since the risk is small, cardiac screening programs for marathons are uncommon. However, this review was not an attempt to assess the overall cardiac health impact of marathon running.

A 2006 study of non-elite Boston Marathon participants tested runners for certain proteins that indicate heart damage or dysfunction (see [[Troponin]]) and gave them [[echocardiogram]] scans, before and after the marathon. The study revealed that, in that sample of 60 people, runners who had averaged fewer than {{convert|56|km|abbr=on}} of weekly training in the 4 months before the race were most likely to show some heart damage or dysfunction, while runners who had done more than {{convert|72|km|abbr=on}} of weekly training showed few or no heart problems.<ref>{{cite journal |journal=Circulation |date=28 November 2006 |volume=114 |issue=22 |pages=2325–2533 |title=Myocardial injury and ventricular dysfunction related to training levels among non-elite participants in the Boston Marathon |vauthors=Neilan TG, etal |pmid=17101848 |doi=10.1161/CIRCULATIONAHA.106.647461|doi-access=free }}</ref>

According to a Canadian study presented in 2010, running a marathon can temporarily result in decreased function of more than half the muscle segments in the heart's main pumping chamber, but neighboring segments are generally able to compensate. Full recovery is reached within three months. The fitter the runner, the less the effect. The runners with decreased left ventricle function had an average peak weekly training distance of {{convert|55.1|km|abbr=on}}, while those who did not averaged {{convert|69.1|km|abbr=on}}. The marathon was held in {{convert|35|C}} weather. According to one of the researchers: "Regular exercise reduces cardiovascular risk by a factor of two or three in the long run, but while we're doing vigorous exercise such as marathon running, our cardiac risk increases by seven."<ref>{{cite news |url=http://www.livescience.com/10211-temporary-heart-damage-explain-marathon-deaths.html |title=Temporary Heart Damage May Explain Marathon Deaths |first=Stephanie |last=Pappas |publisher=Live Science |date=25 October 2010 |access-date=15 May 2017 |archive-url=https://web.archive.org/web/20170417185619/http://www.livescience.com/10211-temporary-heart-damage-explain-marathon-deaths.html |archive-date=17 April 2017 |url-status=live}}</ref><ref>{{cite journal |journal=Canadian Journal of Cardiology |date=October 2013 |volume=29 |issue=10 |pages=1269–1276 |title=Transient Myocardial Tissue and Function Changes During a Marathon in Less Fit Marathon Runners |vauthors=Gaudreault V, etal |doi=10.1016/j.cjca.2013.04.022|pmid=23910227 }}</ref>