Some Exercise is Great, but Too Much Could Kill You — Mayo Clinic Study : Exclusive Renegade Health Article

Wednesday Jul 18 | BY |
| Comments (31)

Marathons are more popular than ever, but are they good for your health
—or dangerous to your heart?

On March 31, 2012, ultramarathon runner Micah True—nicknamed “White Horse”—was found dead in the wilderness of southwestern New Mexico. He had left days earlier on a 12-mile run. His body was discovered on the banks of a small stream.

An autopsy found the left side of the 58-year-old man’s heart to be enlarged and scarred. The state’s Office of the Medical Investigator concluded True had idiopathic cardiomyopathy—heart disease of an unknown cause—but the changes suggested True may have suffered heart damage caused by chronic excessive endurance exercise.

Now, a new study by the Mayo Clinic suggests that exercise like marathons and triathlons can cause major damage to a person’s heart. We’ve been told that exercise is good for us, and marathons, in particular, are especially popular in America right now. Is it time to change our thinking?

Benefits of Marathon Running?
According to Stride Nation, the marathon is more popular than ever. Over the past 12 years, there’s been a 47 percent increase in the number of marathon finishers in U.S. races. Approximately 518,000 people finished more than 720 marathons in the U.S. in 2011.

Yet while there are more runners, there are also more deaths. In 2009, four runners died during half-marathons in San Jose, California, and Detroit. In 2011, two runners died at the Philadelphia Marathon, all from apparent sudden heart attacks. And many of us know the tragic story of Jim Fixx, author of The Complete Book of Running and the nation’s leading spokesperson for the health benefits of running, who died tragically of a massive heart attack while running alone on a country road. He was only 52 years old.

What are the benefits of marathon running? A lot of people start training for them with specific goals in mind. Many want to lose weight. Some want to jump-start their exercise programs, and need a specific goal. Many believe it will be good for their health, and win them stronger hearts, leaner bodies, and deeper nights of sleep.

Yet according to the Wall Street Journal, “There’s no evidence that running a marathon leads to lasting weight loss.” In fact, since people tend to eat more during training, and then maintain the calorie-count after the race—but take a break on the running—many actually gain weight after the race is over.

Neither do marathons lead to new exercise habits. In fact, many won’t continue with the running lifestyle because of waning interest, busy schedules, and injuries. “If the marathon movement really got people at large to exercise,” said Steven Blair, professor of public health and University of South Carolina, “we wouldn’t have the problems we do” as a too-sedentary nation.

What the Study Found
Researchers from the Mayo Clinic reviewed the results of over 50 studies published between 1991 and 2012 on the health effects of extreme endurance training and competition. They found that more than an hour of intense aerobic activity per day put runners and cyclers at heightened risk of serious heart problems, including an irregular heartbeat, clogged arteries, and scarring.

Habitual marathon runners and professional cyclists, they noted, were five times more likely to have irregular heartbeats than their less-active peers. Researchers theorized that repeated structural changes to the heart occur during excessive endurance training or competition, and when people take part in these activities multiple times over several years, scar tissue can form and weaken the heart muscle.

In fact, exercise more than an hour, and you experience “diminishing returns,” according to lead author James H. O’Keefe.

How to Keep it Healthy
Of course, this study doesn’t apply to most people who aren’t engaged in regular intensive athletic training. For the majority of Americans, more exercise is in order—not less. The key here is moderate, regular exercise, without extreme durations or intensities. In fact, other studies have shown that running at moderate speeds is linked with a lower risk of death from any cause compared to not running at all.

The message is not to fear exercise, O’Keefe said, but to practice moderation. But if you are engaged in regular running or cycling, how can you tell if you may be at risk?

According to a 15-year observational study of 52,000 adults, the highest degree of survival and health was found for those that:

  • Ran less than 20 miles a week
  • Ran at speeds of six to seven miles an hour (about a 10-minute mile)
  • Ran 2-5 days a week

Those who ran more than this at faster paces had no additional survival benefits.

Other signs that you may be doing more than your body can handle include tendinitis, stress fractures, and other overuse issues. If you’re suffering from any of these, cut back on your miles.

As to how many marathons per year to run, researchers aren’t sure. Where the damage starts to occur depends on the person. Aiming to run three in one year may be too much—O’Keefe suggests against it. One a year may be fine. In fact, a 2010 study in the New England Journal of Medicine noted that the rate of deaths in marathons continues to be very low, between one in every 100,000 and one in every 200,000.

Finishing even just one marathon, however, is associated with temporary damage to a runner’s body. Research shows that 30¬–50 percent of runners showed increased levels of enzymes and biomarkers typically released during heart attacks and associated with heart failure. Usually these go away within a month after the race.

As you’re setting your fitness goals, realize that most likely, marathons, triathlons, and cycling races won’t make you healthier, and may even cause some health damage.

Kev’s Thoughts:

I love the idea of running for hours in the woods. I used to do it.

I’ve run a few trail marathons and a few more road marathons. These days, not as much. It’s not that I don’t like to run as much, or that I’m scared of not being as healthy as I can — it’s just because I don’t have as much time.

The story of Caballo Blanco (Micah True) in “Born to Run” was intriguing and mysterious and his legacy will “ride” for much longer in long distance and ultra-running circles.

But, yes, it’s important to stress that too much of anything, can be too much.

One of my mentors from afar — that I was finally able to meet — Dr. Phil Maffetone has been teaching long distance and endurance athletes to chill out for years. What happened when they did?

Their performance improved.

Maybe this is just the clue that’s needed to keep your exercise routine in balance and your body healthy and happy for many decades to come.

I can’t say I’m done with marathons, but I am done with training more than 25-30 miles a week — for me there’s just not enough time in the week to make that a priority and based on the evidence here (which I already suspected), I probably will be healthier doing other things — like hanging out with family, the new baby, or friends.

Do you run marathons? What do you think of this study?

* * *

Photo courtesy joshhikes via

Zelie Pollon, “Ultramarathon Runner Micah True Died from Heart Disease: Autopsy,” Reuters, May 8, 2012,

Kleph, “The Marathon—More Popular Than Ever,” Stride Nation, February 28, 2012,

Kevin Helliker, “The Fleeting Benefits of Marathons,” Wall Street Journal, October 6, 2009,

Kathleen Doheny, “Can Too Much Exercise Be Harmful?” WebMD, June 4, 2012,

John Robbins, “What Should We Learn from the Deaths of Fitness Icons,” February 10, 2011,

Christine S. Moyer, “Too Much Endurance Running, Cycling Might Weaken the Heart,” American Medical Association, June 18, 2012,

Kelly O’Mara, “How Much Running is Bad for Your Heart?” Running Competitor, June 2012,

Kevin Gianni

Kevin Gianni is a health author, activist and blogger. He started seriously researching personal and preventative natural health therapies in 2002 when he was struck with the reality that cancer ran deep in his family and if he didn’t change the way he was living — he might go down that same path. Since then, he’s written and edited 6 books on the subject of natural health, diet and fitness. During this time, he’s constantly been humbled by what experts claim they know and what actually is true. This has led him to experiment with many diets and protocols — including vegan, raw food, fasting, medical treatments and more — to find out what is myth and what really works in the real world.

Kevin has also traveled around the world searching for the best protocols, foods, medicines and clinics around and bringing them to the readers of his blog — which is one of the most widely read natural health blogs in the world with hundreds of thousands of visitors a month from over 150 countries around the world.


Comments are closed for this post.

  1. zana says:

    Well, this comes as a no surprise to me! The legends about the first marathon runner we know of, Pheidippides (or Philippides), cannot agree on the distance or the route he ran, but they all state that Pheidippides dropped dead after it.

  2. Brianna says:

    It supports what I’ve had a hunch about for a while. Honestly, I believe people ignore the pain signals their bodies start to send them when they are overdoing it. Exercising a lot is no fun, but in small spurts (15-30 mins)? Tons of fun. I think we are built for that – and perhaps that’s why there are studies that also show the great benefits of interval training, and even just moderate exercise, on a consistent basis.

    This is just like America – if exercise is good for you, then a BUNCH of exercise must be even better! If raw food is good for you, then nothing but raw food is even better! I understand the logic, I really do. But, if the results show you something different, i.e. if your body, specifically, tells you to stop, I think the best thing you can do is listen, reassess, and retest your theories.

    Whew! Great info gets me going 🙂 Thanks Kev!

  3. hyesun says:

    yep, it’s true! many paleo health leaders/docs have been talking about this for a while – dr. al sears, mark sisson (i think), and others. i used to do marathons and sustained aerobic exercise but now i just walk a lot and do HIIT every once in a while. and strength train a couple times a week.

  4. gail says:

    Really informative.

  5. Valentina says:

    I wonder how diet impacts these results. Also, I find the author jumps too much to general conclusions on sports while basing his studies only on running. I would like to see studies on other sports, such as swimming, team-sports, weight-lifting, etc. As different sports strain the body in different ways, I doubt that what applies to running applies to everything else in the same manner.

  6. Lance says:

    Wow, i think there are a lot of factors to consider here. I think this study is useful as a starting point for discussion but I don’t find it nearly conclusive enough. I think there is a lot of good information out there that points to the fact that when you start to run at more extreme levels, you’re ultimately doing a little more harm than good. But for some, I think at that point running is something they enjoy so much it’s worth it.

    I think what’s really interesting about running is incorporating something like bare-foot running. That is a growing trend right now and for good reason. This is an excellent resource for anyone interested in the subject:

    In regards to this study, I would also be very curious to see what kind of diet people had as well. I think that’s a very important piece to look at.

  7. Siscu says:

    As always the health of each study participant was not accurately charted.

    What is healthy for one may not be for another. I believe that a healthy – by healthy I mean a person with perfect levels of vitamins, minerals, amino acids, enzymes, fats, hydration, etc. – person will see none of the negative effects that these studies mention.

    The big problem is that everybody claims to live “reasonably” healthy when the truth is that the majority does not live healthy lives – AND then, yes, sports is unhealthy!!! (not talking about exercise – as Jon Barron says: move or die)

  8. Cameron Day says:

    Over training in any form of exercise is bad for the body. This is obvious, but often ignored in the “more is better” mentality.

    Avoiding over training is actually pretty easy, when you take a big picture view of the topic.

    Move and exercise in ways that you enjoy, stop after an hour, make sure you’re recovering properly and take a week off every 3-6 weeks.

  9. Uffe says:

    Please read a great book called:
    Nathan Pritikin, Diet for Runners.
    Remember most runners has a very bad diet, that the problem!!!

  10. George says:

    It is commonsense that excessive exercise can lead to damage to the body. Olympic athletes have trained themselves over many years to be what they are, but even they admit that there is a time to retire to a more relaxed lifestyle. Moderate exercise is indicated for the average person each day, not that we always do it. If you are unhealthy at the beginning, increase the exercise gradually; that appears to be the correct approach.

  11. Beverly says:

    Always wondered about that. I have tried to do what seems right, to listen to my body , with everything food I eat, vitamins I take, so learn to listen to you, I use adult stem cell nutrition,

  12. zyxomma says:

    For me, running is for flight or pursuit. If I just missed my bus, I’ll sprint to the next stop to catch it. I think the stress (on knees, ankles, feet, and yes, the heart) is too much to make running worthwhile as exercise.

    That said, most Americans seem to think feet are for pushing pedals in the car. Here in NYC, we walk a lot — at least a couple of miles every day, for me. Fortunately, I live in a very walkable neighborhood, with a plethora of health food stores, live food stores and restaurants, and other great amenities. Many of my fellow citizens can’t even walk to a so-called convenience store; it’s too far from home.

    Marathons are not for me. If you like them, take it easy on yourself.

  13. Marina says:

    Thank you Kevin for sharing this great information. I am in the midst of training for my 50 miler on trails ( race is in October) so my mileage is slowly increasing as each month approaches.. This is something that I have been thinking about so I appreciate this. I will keep this in mind as I continue to train for trail marathons and ultra marathons.
    Peace & Veggies

  14. Lois says:

    Most of these deaths could be because they did not have the minerals that they needed. That is what ‘sweat’ is and water does not replenish the minerals that are lost. neither does Gaterade which only has 2 minerals and you need many more than that.

  15. Kev,
    Congrats on the little one!

    Great post. I run Ms and Ultra Ms. Does the study consider:
    – How someone runs? Is their technique low or high stress/impact?
    – How intensely someone runs, meaning heart rate below or above the high-stress “flight or flight” response?
    – How consistent the running program is? Or is run/train hard, then layoff due to high stress, injury or other?
    – What the person’s health philosophy is? Is it live/run to eat (whatever they want … high stress) or eat (healthy) to live/run?
    – What the person’s fitness mindset is? Is it external (high stress mind over body) or internal (mind/body enjoyment)?
    – Is the person’s fitness program balanced?
    – Is the person’s life balanced or high-stress for other reasons?

    I doubt it. How many people run, eat, live, and/or think in ways that are very high stress? My guess is most, so a study that looks at people who “run” seems rather broad. My guess is also that people who run more than the recommendation train harder and eat harder (thinking they can eat whatever they want).

    Thanks for helping me rethink lower stress in balance; even at long distances.

  16. Uffe says:

    It is only Americans there have over training problems.Most runners use the SAD diet, that will kill you if you run or not. If you run on a low fat vegan/raw vegan diet you will have no problems. Read the new great book: Running with the Kenyans, they run 100 to 150 M a week and eat a very simple low fat diet (max 10%).
    In the low fat raw food movement (80/10/10) we have a number of super runners and they and they run Ultra-marathons and are in great shape with no problems. Most problems are a shoe problem, use or similar barefoot sandals and you will have no problems. Shoes are the reason for knee and foot problems.
    Have a great run

  17. Danny Carroll says:

    I agree with David on this. Marathons die from heart attacks because they think running gives them the ability to eat what they like. I am an ultra marathoner and used to be exactly the same. 5 years on atkins managed to destroy my health. I am now vegan and it has made a huge difference to my health and running capacity.

    I have a suspicion that you can exercise too much but am not convinced that the studies as presented are conclusive, especially as the affects of diet are not clearly shown. Some interesting thoughts but there still more work to do to isolate the specific affects of long distance running. Try running through the mountains all night, its the most amazing experience!

  18. Sandi Seegert says:

    I am living proof of this…after years of teaching fitness classes, sometimes 5 or 7 per day which always included high intensity, I began to question whether or not I was doing myself any good, since I was feeling totally exhausted all the time. I posed this question to one of the nationally known certifying organizations and they had no answers for me. No one had ever done a study on the “dangers of too much exercise” but in my gutt I knew the answer. Sure enough, when I went to the dr. complaining of stress and exhaustion, (but funny, they couldn’t understand it cuz I was the picture of health!!) they found a “slightly enlarged heart”. I cut back to two classes per day, (got a script from my dr. for that) and eventually quit that job. That was in the early 90’s. Science has come a long way since.

  19. Steve says:

    Marathon runners eat more food than other people. Does it stand to reason the runners on a SAD diet would have an increased chance of heart problems, while the “plant based diet” runners didn’t? Could it be that marathon runners might be turning up the clock on something that may happen down the road if they didn’t run, while marathon runners who eat right increase their health benefits? I bet most sports bring with them an increase in the number of deaths. But is that because of the sport itself, or the health problems that were there to begin with?

  20. Dave from Texas says:

    This one hit a nerve, and prompted a reply. These are good comments, very incisive. To me,this bears a very similar path of thinking as so much of what I have heard from Kev. That is, find out through trial and error what is best for YOU. Everyone has different tolerance levels, and the types of questions David offers are very beneficial. This sounds so much like Kev’s search for his ideal diet. I have known people who could tolerate so much more than I could with no problems, but with me it was so dependent on my biomechanics and how I was built, as well as a host of other factors (time, family, business trips, etc. etc) that I just could not do it because they said it was the way to go. Same with all the information available at the time on ideal training routines.

    I ran 8 marathons, hitting seven “walls”. The one that I ran well fueled me to run all the rest because it was so exhilerating!

    All told, find your “Golden Mean”!

  21. Lori Sage says:

    I ran over 30 marathons from age 26-46. I was always very aware of being careful not to overdue mileage – just a sense that too much wasn’t healthy in the long run. I was also really interested in Qi Gong and the idea of less outward energy expenditure but with inward breathing and soft exercises you could maximize your results with minimal effort. I can’t say I fully experienced this for I was addicted to the physical aspect. I still think it’s the way to go if you want to do endurance sports. At the start line of my last marathon at age 46 I was looking at all the people surrounding me, people I’ve seen running for years. Most had knees bandaged, upper bodies were atrophying and they just looked old. A woman who I had raced against and hadn’t seen in years who was in my age group looked to be in her 60’s! I thought wow, and this is suppose to be good for you! I felt very lucky at that moment to be uninjured and looking pretty young in comparison to most and quite certain that this was probably going to be my last marathon(although I never say never to anything…). I wasn’t sad, just grateful that I had gotten to experience so many amazing
    races and that I had taken care of myself with good eating, supplements and a balance with running. To be honest if I hadn’t of ran marathons I would have probably been an alcoholic. Runs in my family and I had the tendency. I chose to run but I also chose to be healthy in other ways. Although I don’t run marathons I do hike a 10,000 foot mountain once a month which serves as my extreme fix. I just turned 50 this year and feel like I’m 30!

  22. MaryKatherine says:

    I am a big fan of Dr. Joel Fuhrman and have always found interesting his hypothesis that we want optimum nutrition and fitness without really fast metabolisms – a really fast metabolism is like a really hot fire. Just like the log burns out faster, so does our body. The faster you burn out, your performance and life span suffer. I noted in his recent talk at the latest longevity conference he said studies have shown the longest lived men consume on average 1500 calories a day, women 1200. One simply couldn’t maintain body mass even with the lower calories a nutrient dense, plant based diet provides with that caloric consumption. I am understanding more and more what Donna Gates means when she says we given only so much energy in a lifetime and we need to think carefully about how we use it.
    As I get closer to 60, I am far more aware of how I choose to expend mine. I just updated my bike to upright handlebars that are easier on my joints. I can’t go as fast, but instead of being hunched over, I’m upright and really seeing the scenery around me. I might not go as fast, or get the same calorie burn; but, I really enjoy the ride!

  23. Derek says:

    While I don’t think most people would ever reach the point of too much exercise, I’m also not a huge fan of marathon style training.

    I think from both a health and physical appearance perspective, more intense training and including resistance training is the way to go.

    This may seem vain, but I’ve never seen a marathon runner with the kind of body I would want. Sprinters on the other hand are some of the most all-around athletic and fit people out there.

  24. Ed says:

    Hi, the Gianni family, so cool. Way back in 1968 a military doctor started a national craze,please remember in 1968 it took a military doctor to start a national craze. “VO2 max” the fitness level of fighter pilots was the prize,how to achieve it came in the new book “Aerobics” a new term in the public eye was the natural name for the book because Dr Kenneth H Cooper had decades of work put into the fine tuning of aerobic exercise to maximize “VO2 max”. He noted that the runners’ high existed as many of his military subjects enjoyed longer runs.Still he stuck to the results of data, his book plainly stated that, If you run more than 3 miles a day, you were doing it for reasons othere than health.

  25. Ed says:

    Weird macho, most replies are focused on the correct way to run yourself into the ground. I can do it

  26. Ed says:

    glutithione redux,eyes on the prize, make antioxidants more than a transitory addition, the halve life is nothing without a glutithione redux levels to reuse what might be lost.

  27. Dianne says:

    I have a friend that volunteers at a heart institute on Sundays. A marathon was held one Sunday and she was shocked that 6 marathon runners were admitted that day for heart attacks. That certainly was a shock for me as well. I used to run, and have found that I’m much happier as a walker. Great article Kevin.

  28. the article Some Exercise is Great, but Too Much Could Kill You — Mayo Clinic Study : Exclusive Renegade Health Article did not have the Mayo clilnic reference to the study. I would like to read the actual study. Please let me know what it is called so I can find it. Thank you

  29. Sue Rushford says:

    Yep, I can relate – ran 6 marathons (all around 5 hours) and countless half marathons – finally decided to retire from marathon running after this past one – had ilio-tibial band syndrom in one knee during Season 2; the other knee during season 4; then plantar fasciitis all during season 6 – had to limp the 2nd half of the last marathon. Plus, my holistic health practitioner told me my adrenals are shot & I really need to quit the distance running. So did not run for 6 months – just recently picked up shorter distances – about to go for an 8 mile run right now cause I had previously signed up for just one more half marathon in September so just training easy – so far so good – injury free 🙂 But yes, my original impetus was weight loss – I could not get the old the more I run, the more calories I burn, the more fat I’ll lose lie out of my head. I now know this has driven my adrenal cortisol levels out the window and probably affected my heart (I’m a ‘high raw’ vegan), so I have been concentrating on weights & martial arts – just taking it easy on this one last half – there is still something therapeutic – something I still love about running – even if it would be healthier for me to meditate horizontally instead.

  30. We have an old saying out here in the Pacific Ocean, Island of Saipan, “too much of anything is not good”; it applies to excessive exercise.



  31. Mike Q says:

    Great info and article. I have read and heard about this from some other sources (Dr. Mercola being one), and it is interesting and I would have to agree. I’ve never been a big long distance runner and prefer to do short burst speed training (keeping it to under a 100 yard intervals) so am a little biased as well I suppose. But I started to think about other civilizations and mammals as a result of the topic and are there really any species that run that long of distances at one time without stopping to rest? I know there are probably some tribal type civilizations through history that have been known to travel/run long distances in a day but again without stopping? Or even day after day like many do when they are training? I’d be interested to know if anyone has good evidence/research on that. I feel like as mammals we run to hunt/kill prey or run away from predators. This to me includes short burst movements and sprinting. I don’t believe the chase last 20 plus miles but then again I haven’t been chased by any bears recently.

    Comments are closed for this post.