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Ultra Marathons Might Be Ultra Bad for Your Heart

The views expressed are those of the author and are not necessarily those of Scientific American.


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extreme endurance exercise heart

Image courtesy of iStockphoto/Maridav

If getting some exercise is good for you and getting lots is even better, then hours upon hours of intense exercise must be best, right? Perhaps not.

Many people feel obligated to hit the gym or the trail every now and then to help keep off the extra pounds. But people who run ultra marathons (usually 50 kilometers or more), ride in long-distance bicycle races, compete in Ironman triathlons or even just train for consecutive marathons are not usually doing it just to stay trim. Nevertheless, long-term health benefits (stress injuries aside) of so much exercise are usually presumed to be a bonus.

A new study, published online June 4 in Mayo Clinic Proceedings, suggests, however, that this “excessive endurance exercise” might actually be putting people at risk for permanent heart damage and possibly lethal cardiovascular events.

“A routine of daily physical activity can be highly effective for prevention and treatment of many diseases, including coronary heart disease, hypertension, heart failure and obesity,” James O’Keefe, of the Mid-America Heart Institute of Saint Luke’s Hospital of Kansas City and co-author of the study, said in a prepared statement. But after reviewing the literature on extreme-endurance event participants, he and his colleagues found evidence that over time this type of training might be changing people’s hearts—and not for the better.

The researchers found that many of these athletes had temporarily elevated levels of substances that promote inflammation and cardiac damage. One study found that as many as half of runners in the midst of, or who have just finished, a marathon show these spikes, which can last for days after an event. And over time and with repeated exposure, these compounds can lead to scarring of the heart and its main arteries as well as to enlarged ventricles—all of which can in turn lead to dangerous irregular heart beats (arrhythmia) and possibly sudden cardiac death.

“Physical exercise, though not a drug, possesses many traits of a powerful pharmacologic agent,” O’Keefe said. “As with any pharmacologic agent, a safe upper dose limit potentially exists, beyond which the adverse effects of physical exercise, such as musculoskeletal trauma and cardiovascular stress, may outweigh its benefits.”

Earlier this year ultra runner Micah True, also known as Caballo Blanco, made famous by Christopher McDougall’s book Born to Run (Knopf, 2009) for running with the Tarahumara tribes in Mexico, died at the age of 58 while on a relatively short trail run. The medical report concluded that he had a scarred, enlarged heart and likely died from arrhythmia.

But plenty of people who do not train with the Tarahumara might be at risk. Some 500,000 people finished at least one marathon in the U.S. in 2010, and some 70,000 people run ultra marathons around the world each year. Screening for factors to find people who might be at a particular risk so far is unproven and would likely be expensive. So the researchers suggest that athletes dial back intense exercise to about an hour per day (sessions can be longer if exercise is less rigorous) or at least have regular visits with their doctors to check up on their heart health.

An analysis published May 30 in PLoS ONE also highlights potential downsides of exercise for some people. Claude Bouchard of the Human Genomics Laboratory at the Pennington Biomedical Research Center in Baton Rouge Louisiana, and his colleagues report that in many exercise studies, moderate to intense exercise elevated one or more indicators of risk for cardiac disease or diabetes in a subset (about 10 percent) of the population in the analysis. The authors did not follow the subjects to see if these people were actually more likely to have poor health outcomes, however. And for the rest of the subjects, most of them saw improvements in these risk factors.

But the new findings do not negate the benefits of regular exercise for most people. It adds an average of seven extra years of life expectancy, and it also increases the likelihood that people will spend more of those years relatively trim and in good health. “Exercise is one of the most important things you need to do on a daily basis,” O’Keefe said. But, he noted, “extreme exercise is not really conductive to great cardiovascular health. Beyond 30 to 60 minutes per day, you reach a point of diminishing returns.”

Indeed, a long-term study of 52,000 runners found that those who ran one to 20 miles a week spaced out over two to five days and at an 8.5- to 10-minute mile lived longest.

Indeed, these days, the best bang for your buck seems to be a daily short session—just 20 minutes or so—of intense, interval-based exercise, such as repeated bursts of intense running, biking, swimming or strength training with short recovery periods in between. And, hey, that’ll also leave you with a heck of lot more free time than a daily 20-mile training run.

Katherine Harmon Courage About the Author: Katherine Harmon Courage is a freelance writer and contributing editor for Scientific American. Her book Octopus! The Most Mysterious Creature In the Sea is out now from Penguin/Current. Follow on Twitter @KHCourage.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Dr. Strangelove 3:51 am 06/4/2012

    I’m skeptical of this finding because only 10% of the population had elevated health risk. 90% had reduced health risk. You should go with the general rule. The 10% probably already had health problem to begin with.

    Our experience with vigorous exercise is good. My brother competes in ultra marathons (it’s 100 km, not 50) and triathlons. He had asthma and arthritis. It disappeared when he started exercising vigorously. I was fat before I started running, swimming and weightlifting. I lost the fat and developed the muscles. They’re not big muscles but chiseled.

    Link to this
  2. 2. machuu 10:47 am 06/4/2012

    This doesn’t sound very convincing. I couldn’t get ahold of a copy of the vague June 4th article in MCP, but the link in that sentence leads to a 2002 article about heart failure caused by a genetic defect.

    As for the PLoS ONE Analysis “Adverse Metabolic Response to Regular Exercise: Is It a Rare or Common Occurrence?”, 5 out of 6 of the referenced studies looked only at sedentary or obese individuals, which is not a sound comparison for discussing any kind of athlete.

    Link to this
  3. 3. vanessaruns 11:48 am 06/4/2012

    I’m upset by the inaccurate implications around the Micah True example. If you’ve done any sort of basic research on Micah’s deathq45

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  4. 4. vanessaruns 11:57 am 06/4/2012

    I’m upset by the glaring inaccuracies around the example of Micah True’s death. If you’ve done any sort of basic research on Micah, you’ll find that his condition was pre-existing and doctors said that ultra running very likely extended his life.

    Here is a more accurate account of Micah’s death by the New York Times. It’s not a scientific article, but unfortunately seems to contain research and validity than this one. The comments section contains more medical info posted by Maria Walton (his girlfriend): http://www.nytimes.com/2012/05/21/sports/caballo-blancos-last-run-the-micah-true-story.html?pagewanted=all

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  5. 5. ivaughn 12:32 pm 06/4/2012

    Can someone please provide a citation? There are no articles published on June 4th listed at the Mayo Clinic Proceedings website. It is very difficult to know if the summary presented here is reasonable when the paper is not yet publicly available.

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  6. 6. fitz1j 12:54 pm 06/4/2012

    This is a scientific journal, no? Am I really reading “Research hasn’t been done and is expensive, so we are recommending people don’t do the thing we haven’t researched?” Ms. Harmon, I suggest that you take up a exercise regiment that includes some of these long, intense workouts and see what happens to your perceived quality of life on a day-to-day basis. I highly doubt you’ll find it has decreased. Isn’t that what we’re all really after?

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  7. 7. almondine3 1:21 pm 06/4/2012

    Do you have a citation for this Mayo Clinic Proceedings? Perhaps an NCBI ref, or at the very least an author list or title? Some of us do have access to these journals and would enjoy looking at the article for ourselves…

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  8. 8. leecris 2:53 pm 06/4/2012

    I looked on the Mayo Clinic Proceedings website to see if I could find a citation for the article. The next issue will not be online until Thursday, June 7; the June issue, unlike previous issues, will NOT be available free as Elisevier has now taken over as publisher. You will have to access the article by subscribing, paying for it singly, or through your library that has a paid subscription.

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  9. 9. loureiro 5:54 pm 06/4/2012

    well, the thing that isn’t mentioned is the age of the practioner. If someone is very young, he will start with short running for instance, but as soon as he trains himself, he will take the exercise more and more serious, because he feels it makes good for kim. That’s inquestionable… But as we age, we don’t feel quite the same thing. It’ s natural.. we are not eternal beings. If we insist in a kind of masoquism, we sure will hurt and make fragile our muscle and organic structure.

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  10. 10. AndyJ 8:48 pm 06/4/2012

    I have run more 50-100 milers than I can remember. Few ultra runners show up with only a one hour per day of training in the last month. That is a formula for serious problems and you’re not going to get a buckle or finishers T-shirt. Most who play at this level have base weekly training mileage of 50 miles or more. Most of us are there solely for the fun of it all. Few will get to the winners circle. The article indicates a high degree of foolishness and /or egoism in the runners. A few marathoners may feel they can run with the best. The difference in preparation and training from marathon to ultra is greater than from 10k to marathon. One thing an ultra run teaches is that one should be humble and aware of their condition… not every run is fun or beautiful.

    If one cannot put in the training, please stay home, crew, man an aid station or help in some other way. Most runs are in the less populated spaces and nobody has a cell phone to call in your rescue.

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  11. 11. Dr. Strangelove 1:25 am 06/5/2012

    Ms. Harmon, intense exercise is relative. Your prescribed 20-minute intense exercise is not intense to some people. One hour running or swimming is moderate to me. That’s about 8 km run or 1.5 km swim. I don’t get really tired at that pace.

    Instead people can start with 20-minute exercise and progressively increase the time as they get more physically fit. Later they will find 20 minutes too easy.

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  12. 12. David Marjanović 9:33 am 06/5/2012

    You will have to access the article by subscribing, paying for it singly, or through your library that has a paid subscription.

    Or, y’know, e-mailing the authors and asking for the pdf.

    Link to this
  13. 13. ironjustice 5:16 pm 06/5/2012

    The increased death risk may be due to the fact , exercise causes hemolysis.
    “Foot strike hemolysis”
    Hemolysis leads to increased iron , hemosiderin , in the tissues.
    “Hemosiderinuria caused by intravascular hemolysis”
    Cardiomyopathy is reversed by iron reduction.
    “Reversal of haemochromatotic cardiomyopathy”

    Link to this
  14. 14. Cervenec 10:31 pm 06/6/2012

    I guess all the long distance running is killing off the Tarahumara mentioned in the article. Perhaps that’s why there are so few of them.

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  15. 15. storm55 9:48 pm 07/15/2012

    Something like this in the video should come out soon – “sports gear turns sweat into energy”
    http://www.allgoodread.com/first/2012/07/-sports-gear-to-turn-sweat-into-energy.html

    Link to this
  16. 16. xuniltoor 4:29 pm 09/3/2012

    As a hard core runner for 25 years I can truly say that since I switched to interval training I feel much better. My legs and core are more muscular and I am much stronger. I went from having a sickly marathon runners build to one of sprinter. I still run the occasional 10k for kicks but I will never go back to 12 miles a day. Intervals pull the fat off quick and let you keep the muscle. I am still a White Horse and David Goggins fan (who also has a heart problem) though. No Badwater for me. Ill take the hundred yard dash any day.

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