|LETTER TO EDITOR
|Year : 2017 | Volume
| Issue : 2 | Page : 81
Marathon Running for Amateurs: Benefits and Risks
Department of Medicine and Intensive Care, Hinduja Hospital, Mumbai, Maharashtra, India
|Date of Web Publication||31-Mar-2017|
Hinduja Hospital, Veer Savarkar Marg, Mumbai - 400 036, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kapadia F. Marathon Running for Amateurs: Benefits and Risks. J Clin Prev Cardiol 2017;6:81
I really enjoyed the well-researched review by Burkule  on the risks and benefits of marathon running for amateurs. While I generally concur with most statements, I feel some clarification is required. The bottom line is that a hypothesis generated (J-shaped mortality effect) in the review is presented more like a conclusion in the abstract.
The hypothesis was generated mainly from the Scandinavian trial  in which the definitions and reporting of exercise intensity were fairly vague. The relative risk for mortality for strenuous joggers was 1.97, but the 95% confidence interval was 0.48–8.14. These data are close to random and can be interpreted either way. Mainly from this, the author has stated in the abstract “The epidemiological studies suggest a 'reverse J-shaped' relationship between running intensity and cardiovascular (CV) mortality. The highest benefits of reduction in CV and all-cause mortality are achieved at a lower intensity of running while the benefits tend to get blunted at a higher intensity of running.” It may not have been the author's intention to convey this as scientific proof, but all my colleagues who cite this paper believe this to be proven causation rather than association. They mistake a hypothesis for a conclusion.
The author looked at surrogate data, such as raised biomarkers or imaging changes, but the relation of these to clinically meaningful outcomes is completely unknown. They could equally be part of an adaptive strengthening physiology or be the forerunner to an exhausted response leading to clinical disease. We really have no outcome data that reliably points to which surrogate changes are associated with poor outcomes. It is a mistake to assume that all physiological parameters outside the normal range necessarily imply impending disease.
The author stated that fewer deaths occur in half than in full marathons. It may be that intensity not distance is the main risk. On June 11, 2014, the Mumbai police competitive recruitment process included a 5 km run in which there were 4 deaths. Similarly, in South Africa on December 2012, there were 6 deaths among 30,000 applicants in a 4 km fitness test. This far exceeds the known sudden death rates in half or full marathons. Medical advice relating to sudden death may be more relevant when directed at intensity of effort rather than distance.
Based on the above, I feel the best advice a physician can give a potential runner is that we do not really know the risks of increasing the distances of running, and the best we can is state that more may not necessarily be better. The official evidence-free guidelines on this topic are merely guesses that reflect the biases of the authors rather than any robust data.
One unrelated clarification, the author states that Homo sapiens have been around 2.5 million years. All the combined humans (H.) species have existed for this long, but H. sapiens have only been around for ~200,000 years.
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Conflicts of interest
P. S Intellectual Conflict of Interest: As a marathoner, I declare a strong bias toward the overwhelming medical benefits of liberal exercise.
| References|| |
Burkule N. Marathon running for amateurs: Benefits and risks. J Clin Prev Cardiol 2016;5:113-24. [Full text]
Schnohr P, O'Keefe JH, Marott JL, Lange P, Jensen GB. Dose of jogging and long-term mortality: the Copenhagen City Heart Study. J Am Coll Cardiol 2015;65:411-9.
Harari YN. Sapiens: A Brief History of Humankind. Harper, USA: HarperCollins; 2014.