Cycling Wed Exercise inflammation

CW: Is marathon running really that safe?


Imagine the inflammation that the endurance-athletic community would have been spared?

If only Pheidippides had lived. I mean, what was the rush? The battle had already been won. Athenians could have waited another few hours (or days) for the good word on the battle of Marathon. It’s not like someone was tweeting in 490 B.C.

Dang it. For if Mr Pheidippides had not suffered sudden death after that long run, the notion that enduring 26.2 miles be so defining might never have stuck. Runners could have hung their 10K times on the self-esteem peg. And those crazies in Hawaii might have decided 112 miles of riding after swimming 2.4-miles was enough.

But I don’t have a time machine. There were no AED’s in 490 B.C. (And Mr P would not likely have met NCD guidelines for an ICD anyways.)

So humanity is stuck with marathons—an arbitrary, excessive and I believe, dubious way of proving one’s mettle. But I’ve been outvoted. More and more, just running, getting fit, being fast, isn’t enough; one must finish a marathon.

Coronary Calcium

This, despite mounting evidence that the inflammation that comes with the slog—and yes, for the majority of marathoners, it is a slog—may confer a not so healthy outlook. Why all the calcium in coronary arteries, scars in the right ventricle and those Marathon rats—you know, the Canadian rodent equivalents of endurance athletes? (Dear athletes, research Marathon rat studies at your own risk; it’s scary.)

These are just the studies. You should ask a regular heart doctor. Each of us can recall vivid cases of seemingly healthy athletes felled by heart attack–in spite of their athletic prowess. Or…is it because of their quest for excess fitness? Could exercise have an upper limit? More may not be better. One would think these concerns, bolstered by emotionally-wrenching reports of runners dying suddenly during competition (or training) would limit the sport’s appeal. But this has not been the case; participation in marathons continues to grow.

In fact, one wonders whether press reports on the dangers of marathoning only enhance the mystique?

So large has grown the controversy surrounding the health concerns of marathon running, that Medicine’s most prominent journal, the New England Journal of Medicine felt the need to publish an uncharacteristically weak study in last week’s edition. In the Cardiac Arrest during Long-Distance Running Races study, researchers from Boston used a registry to compile statistics on cardiac arrests during running events in the US over the past decade.

The five major findings were not that surprising:

  • Of 10.9 million runners included in the registry, only 59 suffered cardiac arrest. That translates into a miniscule 0.5 per 100,000-runner incidence. Pretty small risk here.
  • Of the 59 cardiac arrests, 42 people (71%) died. Though this sounds bad, the 29% survival rate is significantly higher than established rates of out-of-hospital cardiac arrest.
  • Cardiac arrest occurred seven-times more frequently in men. And more events occurred in the latter half of the event.
  • Medical records were available in only 31 of 59 cases. The causes of cardiac arrest followed well-established patterns: over age 35, there were significant coronary blockages present, and for those under 35, the most common abnormality was thickening of heart muscle (hypertrophic cardiomyopathy).
  • Most bothersome were 4 unusual causes of death: In 2, low sodium levels were cited, in 1, hyperthermia, and 1 woman’s death was presumed related to an anorexic BMI of 14. One thesis here would be that these poor souls ran themselves to death.

The researchers concluded that long-distance running is associated with a low overall risk of cardiac arrest. To highlight the safety of marathon running they smartly made the point that it was twice as safe as college athletics, triathlon and more than ten-times less risky than middle-aged people in the 1970s who started a jogging program. They also emphasized the importance of early CPR–an important finding.

The problem with the study came with its spin:

Like any study published in the NEJM, this one generated a great deal of press, some of which was misleading. For instance, the usually reliable NPR Shots blog began their coverage with this over-reaching sentence

“Running long-distance races isn’t going to hurt your heart any more than other vigorous sports,” researchers say. Just make sure you’re fit enough to attempt the feat in the first place.

Senior researcher, Dr Aaron Baggish provocatively said to, “one of the big take-homes is that marathon running is safe and appears to be very well tolerated.”

My take is different:

As the researchers acknowledge, the study had flaws. They admit that the registry may have not captured all the events. For instance, just Googling around for a few minutes turned up 4 sudden deaths in the Detroit Marathon alone. Hmm.

No worries, let’s spot the registry a little underestimation. Even if you quadrupled the number of events, given a 10.9 million denominator, the percentage risk remains low. But looking at only race-day events greatly underestimates the inflammation incurred in being a marathoner. People don’t just show up and run a marathon; they train, and slog, and inflame, and slog some more… and…so on. As stated, but not spun in press releases, were the limits of what the results could say. From the ‘conclusions’ section:

“We cannot comment on the risk or outcomes of cardiac arrest in specific populations, such as elite athletes, first-time race participants, or runners with preexisting medical conditions.”

Limitations of provocative studies rarely get emphasized in the spin. Readers hear that marathon running is as safe as any other vigorous activity. That’s not what the results say to me. What I hear is that when one looks only at the hours of the actual marathon, the number of cardiac arrest events don’t look too awful. What these events don’t speak to, however, are the cases of catastrophes that occur in the hours marathoners live without a number pinned on, which is 99.99% of their lives. The study didn’t look at the weeks and years of prepping for a marathon. Nor did it look at the long-term effects of running many marathons.

Just because we now know that people aren’t dying in droves during races, doesn’t mean we are any closer to understanding how much exercise is too much. Many questions remain, and I find them interesting–from an inflammation standpoint. Think: some stress is good; too much leads to premature disease.

But…and this is a big but…

As a minimalist cardiologist who believes exercise, not pills or procedures, is the best medicine, it pains me to write anything even remotely negative about exercise. People should exercise regularly. This I believe.

For the idea that marathons need be so defining; that to achieve, we have to inflame so.

For this, I’ll blame Pheidippides.

If only he had a bike!


Two postscripts:

One is some advice: If you are over 35 or have risks of heart disease, it makes sense to see your doctor before embarking on the journey of finishing a marathon. You probably don’t need to be radiated by expensive imaging tests. A simple history, exam, ECG, and perhaps a regular treadmill may be reassuring. The data that doing Coronary Calcium scans will prevent death from excessive exercise = Zero.

The second: In the interest of full disclosure, I too was swept up in the allure of the marathon. Chicago 1995—a pedestrian and sufficiently-inflamed 3:08. Qualified to run the 100th Boston Marathon, but never again felt the pull to race that distance. No, I’m not bitter. Just curious.

15 replies on “CW: Is marathon running really that safe?”

Good post. I find the physiologic effects of endurance racing and training on the human body fascinating. The scientific evidence against running marathons won’t deter me though. I’ll take my chances…running my 3rd marathon on Sunday actually. I’d rather go out doing what I love than die from sitting on the couch. Thanks for pulling in the Greek history and a 3:08 isn’t too shabby for somebody simply allures by the 26.2 miles.


You know I love your stuff, but I’m going to have to chime in on this one. After taking on the triathletes, you’ve now gone after us.

Nothing in your post above refutes the general notion that marathon running is safe. No doubt, if you gather 20,000 people and put them through a high physical stress event simultaneously, you’re going to see some tragedies. I suspect most of those cardiac arrests would have happened another time in the near future when less emergency personnel are around to help the victim. Recall, most of these people had underlying heart disease (CAD or HCM) that predated the race. As for hyperthermia and hyponatremia, race organizers have gone to great extremes to prevent these rare problems.

I agree training is also stressful, but for most of us, the stress and subsequent inflammation of the actual race far exceeds the stress of training. I think for most of us competition means going on when your body tells you otherwise. Therein lies the danger.

The mental benefits of approaching a goal that initially seem unattainable and then succeeding are probably not measurable. I have felt these, and I’m sure this has done me worlds of good. Running a 10K, while pretty cool, doesn’t really approach this. Best proof I can offer of this is a documentary “The Spirit of the Marathon” available free on Hulu at
If you can watch that all the way through and not want to pin on a bib again, you’re a stronger man than I am.


BTW: I suspect in a parallell internet there is another Dr. John M, the trauma surgeon, marathon runner who writes about the dangers of cycling: 85,000 traumatic head injuries and 600 deaths a year in the US. Gee, that sounds dangerous, doesn’t it?

Beautiful Jay.

Thank you. I appreciate your comments.

The folly of competitive cycling does indeed make runners look smart.

But the fact that cyclists wrap ourselves around trees, bump our heads on pavement, and duel with cars, does not make coronary calcium and heart fibrosis any less problematic.

I don’t mean to imply one particular sport bests another.

And so I appreciate the clarifying opportunity your comment affords me. To say again, I love exercise. That’s why I’m so interested in these intriguing studies.

I have to disqualify myself from opining on the good and bad physiology about marathons (both ‘training for’, as you wisely include here, as well as ‘participating in’!) because a half-marathon is the longest I’ve run personally. But hanging out with distance runners for almost 20 years has been invariably an exercise in hanging out with a bunch of obsessive-compulsive types who appear quite happily addicted to the activity. They run when they’re injured, they run when they’re sick, they run instead of going to their kids’ school plays, soccer games or birthday parties. (Perhaps you see the same in cycling circles?)

But as a person who’s spent 37+ years in the field of public relations, I’m interested in the spin that the NEJM article has prompted. Until we get studies (GOOD studies, I mean) that differentiate between multi-marathoners, newbies, and cardiac arrest data from the weeks before or after marathon target dates, this one seems a questionable inclusion in the NEJM table of contents.

The NEJM study is important. Regardless of potential weaknesses, it’s the most complete look at run race-related sudden cardiac death that we have.

The 29% rate of surviving cardiac arrest is remarkable. If you’re a runner, your chances of surviving an episode of cardiac arrest may be greater at a running race than in any other out-of-hospital setting.

Most victims had an identifiable, underlying cardiac condition. This isn’t surprising. Those conditions are only identifiable (before death) with medical evaluation. Interestingly, the survivors of cardiac arrest were much more likely than non-survivors to have a primary physician and to have had previous assessment of their risk factors for coronary artery disease (CAD). My take: important to see the doctor before participating.

My last comments relate to “how much is too much?”. No doubt, the runners at a marathon are a diverse group in terms of preparation and training. But I know from surveying my group of athlete friends that even the most avid recreational runners only train a few hours per week. So my question for Dr. John is this…. How do you advocate for routine exercise of 3.5 to 7 hours per week (to maximize the healthy benefits of exercise), yet question the advisability of participation in a marathon on an occasional basis?


“…How do you advocate for routine exercise of 3.5 to 7 hours per week (to maximize the healthy benefits of exercise), yet question the advisability of participation in a marathon on an occasional basis?”

Because no marathoner trains for just seven hours a week.

Larry…Great comment.

First, I concur; there’s no data suggesting that doing one (or an occasional) marathon is harmful. Nor do I believe working up to an occasional 3-4 hour effort once in awhile is detrimental. In fact, it’s probably good.

My reasoning for highlighting the study was that it was spun into an inoculation of sorts. The low event rate during races, however, does not negate the interesting and sobering data on long-term endurance slogging.

What’s more, and maybe it’s just my age and accompanying loss of fast-twitch, but I can’t help question the philosophy of running that long. Remember, for the pros, the marathon can be completed in a couple hours, but for the masses, it’s often more than four. (What’s the point after 4 hours?)

For the record, I think the length of Tour stages is equally dumb. Some of the best racing happens during shorter stages. And maybe riders would feel less compelled to enhance themselves if the distances were more reasonable.

Thanks again.

Wow, what an informative article! I hadnt thought about the negative aspects of marathon running. I am personally a advocate for bike riding, and running a couple of miles. Sad to say that a type of exercise is bad 🙁

Dr.M, curious are there any studies on elite marathoners or long distance runners such as the Ethiopians/native American?

I can’t quote anything off-hand. But I love where you are going with this question.
How much do genes contribute to one’s susceptibility or resilience to endurance exercise?

Good inquiry.

Good article. Reading between the lines, it seems like you don’t think much of coronary calcium scans. Can you say more about that in another article? My father had his first heart attack at 53 and his last and fatal one at 77. Since I’m now 53, I was considering having a scan done. Note that I’ve been doing triathlons (Oly/HIM distance) for 3 years and am likely in better physical condition than when I was 20.

The blogosphere lights up every time one of these reports are published with quotes of “studies suggest” or “according to the latest research”. It just brings up more questions for me than answers. You, Dr. John (as I am sure you are aware) were quoted on Dr Mercola’s blog where he basically condemns Marathons in favor of his “Peak 8’s and buying a recumbent bike or elliptical trainer from his site ( and uses a “recent study” to do so, .

In cycling, you have one of the most notable coaches in the world writing a book for “Time Crunched Cyclists” which is more focused on High Intensity Intervals and shorter (safer?) rides but, is also a proponent of the more traditional LSD rides of 4 and 5 hours at low heart rate tempo.

I really enjoy doing my couple of Centuries a year, but I also want to be around doing the same training rides with my grand kids in 30 years.

Is it is truly healthier to do shorter, more intense workouts and competitions? The competitive juices will always kick in to push that little extra especially in shorter races. Is Crossfit too intense? Peak 8’s? Tabata? When to stop? 1 hour? 2 hours? 3? Cycling over Running? Swimming over both?

I know you don’t have all of these answers, but I will keep coming here for your great insights, that is until you start selling Cyclocross bikes for Heart Health.

Thanks, Mike.

On just the right dose of exercise, for longevity…I dunno. And to be honest, it scares me to agree with Dr Mercola.

A recent observation: for the past month or so, both my wife and I have felt off. The weather here, though mild, hasn’t really allowed for a any ‘big’ workouts. Finally, last weekend we decided that we were going out for a big ride. It was cold, a bit icy, but oh did that 3.5 hours help us get back to our normal sensations. As if on cue, a couple of mates texted me the next day that they felt ‘normal’ again. “Emptying the chamber,” so to speak, restored our balance.

Clearly Ironman is too much and what most of my patients do(n’t) do is too little, but is one marathon or one century per year detrimental? Hard to say. And to complicated matters more, as an early commenter, Bill inquired, does one’s heredity say something about the healthiest exercise? Probably.

It’s good to have certainties: Equating cyclocross and anything healthy seems dubious.

John – Thanks for the blog entry. As a longtime runner and 3-time marathon finisher, I’ve read with interest, and alarm, the various studies that have been published in the past year or two suggesting the possibility of lasting damage to the heart from marathon and/or ultra-running. Enough so that I’ve reduced my mileage during that time and haven’t participated in any long races. But I must say I miss it. And when I read in Runners World magazine about the NEJM study, I was encouraged. Not surprisingly, RW spun the study in an extremely positive manner, i.e., basically as indicating that marathon running is perfectly safe for most people. It’s good to hear a different take on the study from you. But I feel a bit like I’m back at square one: not knowing precisely where to draw the line between healty and unhealthy, in terms of running quantity. I guess the cautious thing to do at this point is to simply continue running, but avoiding longer distance races??

On a different note, I agree with Dan (one of the posters above) in that I’d love to hear your opinions about coronary calcium scans and scores. Are that at all beneficial in assessing a person’s risk of a coronary event? And if not, what do you suggest?

Lastly, would love to hear your take on what is a healthy diet in terms of cardiovascular risk. The internet and blogosphere is full of conflicting views on this point — eg., the Ornish/Esselstyn/Fuhrman crowd (vegan or vegetarian lifestyle) vs. the Paleo/Primal crowd (who argue that saturated fat in various forms is actually good for heart health).

Thanks again for the article. Keep up the good work!!

John – As a new member to this site I would firstly like to say how enjoyable and informative it is. As someone who is rapidly approaching 50 years old, I can’t help but notice numerous reports of ulta-fit men of my age having heart attacks during races.
I read with interest your post on how emotion causes vaso-constriction and potential damage to blood vessels and wonder if these runners were happy- runners or angry-runners? Something that these studies would not include!


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