is ultrarunning unhealthy

Is Ultrarunning Bad for Long-Term Health?

By Jason Koop,
Head Coach of CTS Ultrarunning

Every few years, a narrative emerges that some particular level of exercise is bad for long term health. Sometimes the stories focus on the amount total volume, or the peak of intensity, or some combination thereof. And when those narratives come around, the collective athletic community takes a pause to review the research and what we know to date, evaluates case studies of athletes who have tragically died on the field of play, and tries to make sense of it all. So, when this narrative review titled ‘Potential Long-Term Health Problems Associated with Ultra-Endurance Running: A Narrative Review’ was published in the journal Sports Medicine, I took note (and a deep breath).

Piquing my interest further were two of the review’s authors, Vokler Scheer, MD and Nick Tiller, PhD. If you are unaware of Dr. Scheer’s previous research and work, he is a founding member of Ultra-Endurance Sports Science, a non-profit organization dedicated to scientific and medical advancement in ultra-endurance events. For the last several years, they have contributed immensely to what we know about some of the risks associated with ultramarathon running, such as hyponatremia and acute kidney injury, and they have produced or contributed to many of the medical guidelines that races around the world follow in order to keep runners safe. Mr. Tiller is the author of ‘The Skeptic’s Guide to Sports Science, a scientific advisor to the upcoming second edition of my book (Training Essentials for Ultrarunning, 2nd Ed), and I have always appreciated his no BS, pragmatic approach to controversial topics. So, when these two heavy hitters have something to say, particularly when it pertains to long term health and potential negative consequences of any activity I participate in, I take note.

A system by system look

To examine the issue of long-term health consequences of ultramarathon running in a systematic fashion, the review team decided to take a system-by-system approach. They compartmentalized the body into segments, such as the cardiovascular, musculoskeletal, immune, renal systems, and so forth. They then examined the potential mechanisms for damage within each system, and then reviewed the existing literature. While the body is not merely a grouping of unrelated organs, this approach gave some order to the chaos in this big-picture problem.

Throughout each section, one word stands out: “potential”. The descriptor is in the article a total of 22 times, leaving readers to wonder if the authors are being deliberate or simply without a thesaurus (it’s the former, I assure you).

Potentially, some individuals with large increases in myocardial mass may also exhibit some fibrosis scars.”

Translation: endurance athletes tend to have bigger hearts and those bigger hearts are susceptible to scarring, which is bad.

“Endurance athletes are potentially at a greater risk of EIB (Exercise Induced Bronchoconstriction) owing to high levels of pulmonary ventilation sustained in training”

 Translation: Endurance athletes breath a lot during training and are more susceptible to bronchoconstriction as a consequence.

You can read the whole paper and easily come to the conclusion that the title is merely provocative and the text intentionally ambivalent. But it’s not. It was a deliberate choice by the authors to keep including the word ‘potentially’ because of a) the wide range of responses by each individual to ultramarathon stress and b) the overall lack of research on ultramarathon runners.

is ultrarunning unhealthy

Figure 1-Adapted from Scheer et al 2021

So where does this leave average Jane and Joe Ultrarunner? If you are concerned about your long-term health, should you forego ultrarunning entirely and take up cross-stitching instead? Despite the ambivalence, all of the ‘potentially’ and ‘it depends’ riddled throughout the paper I do think there are some takeaways ultrarunners of all ages should take to heart (pun intended).

Racing might be the biggest problem

Late in the paper, the authors present an intriguing model of what repeated racing potentially (there’s that word again) might to do affect systems over time. As shown below, one bout of race-type stress might have a short-term negative effect on any one system. The research demonstrates this across a number of different areas, as demonstrated in the paper. However, what is unknown (shown by the shaded area in grey) is the time required for that system to repair itself before the next race-type bout so that the associated recovery and compensation makes that system functionally better or the same as the first bout. There simply is no research in this area. However, given how big the ultramarathon overload is compared to day-to-day training, we would be well served to view this information cautiously, particularly considering that ultrarunners race far more frequently than their marathon, half marathon and 10k/5k counterparts.

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Is ultrarunning unhealthy

Physical health is an incomplete view of health

One of the long-standing issues I have had with extrapolation of research to long-term health outcomes is that typically there is excessive focus in one area at the expense of the bigger picture. Take for example the book, “The Haywire Heart”. The subtitle says it all: “How too much exercise can kill you, and what you can do to protect your heart”. Sounds super scary and it would be easy to look at the book and its title and assume that too much exercise is bad for overall health. After all, the main protagonist of the book (the human heart) is one of the most important organs for overall health. And if you compromise the heart in any way, surely you are compromising overall health in the process (note, this is not what the authors convey in the book. It’s just an easy assumption to make).

And we make this leap of faith all the time, unnecessarily correlating narrow physiological aspects like resting heart rate, blood biomarkers, and levels of liver enzymes with ‘good health’.

Ultimately, it is the amalgamation of physical attributes, as well as mental and psychological attributes, that should better fit our definition of ‘good health’.

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With all that being said, I think here’s what we can take away from the state of ultrarunning training and racing as it pertains to long-term health:

  1. There is currently little compelling evidence that normal ultramarathon training is deleterious to one’s physical health.
  2. If you are concerned about the role ultramarathon running plays in your physical health, considering limiting your training to 12 hours per week during peak weeks and racing only once or twice per year. While you’d be hard pressed to find a concrete scientific guideline in this area, both recommendations seem to be safe as well as practical.
  3. Your relationship with ultrarunning should extend beyond the physical. Ultrarunning and training for ultramarathon events should fulfill your psychological and emotional needs as well!

Author’s note- I interviewed one of the co-authors of this paper, Nick Tiller, for my podcast here. 


Scheer V, Tiller NB, Doutreleau S, et al. Potential Long-Term Health Problems Associated with Ultra-Endurance Running: A Narrative Review [published online ahead of print, 2021 Sep 20]. Sports Med. 2021;1-16. doi:10.1007/s40279-021-01561-3

Comments 1

  1. Great insights. Ironic to be reading this while watching three runners go over 300 miles at Big Dog’s Backyard Ultra world championship.

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