Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
9 Jul

The Evidence Continues to Mount Against Chronic Cardio

Chronic CardioIt’s been awhile since I did a post on chronic cardio. I had a good string of them going several years ago, and I thought I’d done a good job explaining why I was so opposed to excessive endurance training. Despite my attempts to clarify, though, I still receive a lot of questions and comments about cardio. People just have a tough time divorcing themselves from the notion that cardio – as much as you can cram into your schedule – is the key to health and fitness. I don’t blame them, really. It’s conventional wisdom, after all, and it’s what I thought for years and years. Clearly, another post is needed.

Evidence against chronic cardio continues to mount, so there’s a lot to cover. But before we get to all the research, I have a few thoughts about the heart.

Here’s the thing about the heart: being an involuntary muscle, it has no say in the matter. It pretty much feels nothing, too. It’s along for the ride. Just like the liver, kidneys, pancreas, thyroid, adrenals, etc., the heart responds to biochemical signals. It’s a demand organ. Minor changes in blood chemistry (epinephrine, cortisol, insulin, lactic acid, hemoglobin-depleted RBC’s, to name a few) cause it to respond by beating faster or slower, forcefully or not, to keep pace with the muscles’ (and other organs’) demand for oxygen and fuel. During exercise, it’s the brain that starts this whole process with a (usually) conscious decision: “I think I’ll run to that tree.” That thought prompts the muscles of the legs to start moving faster and the arms to pump. The new, increased demand for oxygen and added fuel (over and above normal resting metabolism) signals the heart to start to fulfill the demand, to pump harder and faster. It’s obliged to do so. Period. No choice. That’s also why it’s always a bit behind schedule: it takes more than a few seconds to ramp itself up once the action begins and a few seconds or minutes (or hours, in the case of an over-trainer) to ramp down, once it’s over.

The problem with chronic cardio is that we can force our brains to override some of the tiredness (no pain, no gain, pal) and discomfort in the legs – and to a certain extent even the lungs – and keep doing these hard endurance workouts incessantly day in and day out. The ostensible limiting factor is the ability to burn fat or, at the very least, the amount of glycogen still left in our muscles. That’s what eventually brings us to a halt, frequently because we have willed ourselves to keep going through the wall at all costs. But the heart is often over-worked in this scenario, just trying to keep up with that “inhuman” (and inhumane) desire to run, cycle, or swim further and faster in pursuit of…what? A medal? A ribbon? Bragging rights? It can’t say no. It attempts to do as we bid it. And because the heart feels little-to-no pain – unless, perhaps, it feels the REAL pain of a heart attack – it very often suffers silently as a result without us ever knowing. The walls of the heart start to hypertrophy over time the same way a biceps muscle does when you do curls. But do a few too many curls and your biceps will get sore quickly. Force yourself to do a few more and you could even tear something and be out of contention for a few weeks. We know when to stop before that bicep tears.

Cardiac muscle doesn’t tear that way when over-worked, but it does enlarge and thicken with chronic overuse. In some – most – people the thickening is probably not life-threatening, but in some cases, as with dozens of world class athletes I have personally known, this thickening can cause all manner of issues later in life. Atrial fibrillation has become a mild epidemic in my generation of life-long aerobicizers; several of my friends have had pacemakers or defibrillators implanted before the age of 40 to head-off those sporadic life-threatening cardiac enervation problems. A few more friends have lost significant cardiac function and a few have died.

But don’t take my word for it. The silent epidemic of heart issues among endurance athletes is getting serious attention in the research community. Let’s take a look at some of the latest research.

Cardiac Arrhythmias

Cardiac arrhythmias are abnormal electric activities of the heart. An arrhythmia can describe a heart that beats too fast, too slowly, too irregularly, or too “fluttery.” An arrhythmia doesn’t always indicate or foretell heart trouble, but it’s a common risk factor. One of the more common varieties is atrial fibrillation (AF), which describes a fast, irregular heartbeat. AF is strongly linked to stroke and cognitive decline.

Endurance athletes are at a greater risk for atrial fibrillations than the general, non-running public. One recent study of cross country skiers even found that the best athletes, the top performers, were more likely to have cardiac arrhythmias than the rest. Moderate exercisers, meanwhile, are at a lower risk for AF than the general, non-running public. A recent comprehensive study offers several potential explanations for the increased risk:

  • Increased fibrosis (scar tissue formation) in the heart.
  • Myocardial injury to the heart, as evidenced by post-training elevated cardiac biomarkers typically used to diagnose injury. Probably not a big deal so long as you recover fully from your training, but most cardio junkies can’t wait that long to log more miles.
  • Excessive amounts of inflammatory markers brought on by training. These markers have been linked to AF.

Endurance-related AF usually starts off infrequent. The older you get and the more miles you log, the more entrenched and regular your atrial fibrillation may get. Some studies found that around 40% of athletes with AF eventually progress to persistent AF, where it’s happening on a regular basis. That’s the troubling kind of AF that may presage serious cardiovascular problems, like stroke.


It’s totally counterintuitive to think that endurance athletes are at risk for arterial plaque. “You mean to tell me that the wispy greybeard whizzing past my house in short shorts every evening could have clogged arteries? No way.” Maybe, just maybe.

A 2011 study found evidence of carotid and peripheral atherosclerosis in a group of marathoners. Although there was no control group of non-runners in that study, another study compared the arteries of marathon runners to a control group of sedentary non-marathoners. Marathoners had more calcified plaque in their coronary arteries, which has been linked to stroke and dementia. The tricky thing about these cases is that endurance athletes with atherosclerosis don’t evince the regular signs. Whereas your typical sedentary guy with extensive atherosclerosis will probably have all the hallmarks (metabolic syndrome, abdominal obesity, hypertension, etc.), marathon runners with atherosclerosis don’t fit the traditional cardiovascular risk profile.

It might be time to add “trains for endurance athletics” to the list of risk factors.

Oxidative Stress/Overtraining

It’s no secret that endurance training induces oxidative stress on the athlete. That’s how we get better – by encountering a stressor, being broken down a bit, and then recovering stronger than before so that the next time we encounter the stressor, we’ll be better than the last time. Whether we’re talking strength training, marathon running, cycling, gymnastics, martial arts, or even studying for a trigonometry class, we have to challenge our physiology to get better, and challenges to the physiology mean oxidative stress. Problems arise when we don’t let up, when we keep the intensity elevated and the days off few and far between. We’re constantly in that post-workout state, and it starts to look like chronic oxidative stress for all intents and purposes. Even if our times are improving, we’re not truly recovering. It’s a two steps forward, one step back kind of thing.

So. Those are just a few of the reasons I am no fan of chronic cardio (and don’t get me started on the bad backs, osteoarthritis, hip and knee replacements and chronic tendonitis among my former elite endurance peers). A strong will can be a great thing for survival, for business and for relationships, but it can also get you in trouble if you don’t pay attention to your training load.

Having said all that, I am still a big fan of weights, of brief, intermittent interval training and I am all for doing a fair amount of mixed low-level cardio, the kind that doesn’t overstress the heart or involve so much repetitive joint motion that it causes chronic injury. That makes sense in an ancestral context. You’re expending energy at a high rate, but you’re not going long enough that it becomes a liability. Or, if you’re going long, you’re taking it easy enough that you have the energy to make it back home, possibly carrying food.

I’m not even against a long training run or ride once in a while, provided you are trained, rested and allow enough recovery afterwards. I’m even OK with running marathons occasionally or jumping into a short triathlon now and then. As a species, we obviously have the capacity to go long and relatively hard every now and again. It’s the chronic, day-in, day-out long, hard stuff that is counter-productive. If you did that twenty thousand years ago, when your next meal – and that of your entire family/tribe – was on the line, when calories were somewhat precious, when you didn’t have an air-conditioned caravan of trainers, massage therapists, and coolers filled with electrolyte drinks following along after you, you’d be foolish. You simply wouldn’t do it.

That we can run marathons (and do other stupid things) and know that we’ll get out alive is a luxury of modern living. There are so many other less damaging ways to achieve what I would call high-level adaptive fitness by using a variety of training methods, all of which can be cardio-protective and joint strengthening when done the right way in at the appropriate times. Heck, when it comes to hypertension, blood lipids, and type 2 diabetes, walking is just as effective as running – without the potential downsides. Everyone can walk. Everyone thinks they can run, but running is a skill that must be learned. To run with poor form is to welcome injury, doubly so if you’re running an excessive amount. And all this will be addressed in detail in my forthcoming book, Primal Endurance. For now, use your brain and listen to your body.

My point, of course, is that the human organism is made for short, intense bursts of activity laid atop a foundation of frequent slow moving. We aren’t “supposed” to run as hard as we can for two or three hours. We’re not supposed to run with the express purpose of “burning calories.” We can certainly choose to do those activities, and we’ll become adapted (or perhaps inured) to them, and they may even make us “fit,” but they’re not the healthiest, most efficient path to fitness. Chronic cardio is the meandering, roundabout trail that will get you there with a ton of bruises, scratches, a tick or two, and a sprained ankle. Oh, and you might get eaten by a bear along the way.

Your choice.

Thanks for reading, folks. I’d love to hear your thoughts on cardio, both chronic and otherwise. Let me know in the comment section!

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. As a “Chronic Cardio” Success Story featured in the softcover PB, I have a few well-chosen thoughts on this topic of “chronic cardio”. Chronic cardio is a somewhat vague and mostly misunderstood concept, in my opinion. There is a broad spectrum of variables that go into appropriately defining chronic cardio in respect to each individual individually. Variables such as level of intensity, duration of exercise, conditioning of the individual, and their ability to recover from the effort. Is it “easy” on their mind, body and spirit? Do they feel energized or exhausted after their bout of endurance training? Did it raise their cortisol level and did it cause massive systemic inflammation in their body?

    Take for instance, elite Kenyan distance runners spend 90% of their time jogging at a pace which is at a level of intensity equated to a brisk walk for most untrained folks, hence would not qualify as chronic cardio because ultimately chronic cardio is when you overdo high intensity and high duration and do so too often with inadequate recovery.

    As for the various studies, such as about atherosclerosis and so forth, I doubt that the studies took into account the chronic cardio exercisers nutritional intake and status. Endurance athletes are notorious in over-imbibing carbohydrates and high glycemic foods that raise insulin and hence increase plaque in the arteries and so forth, which may be the major contributing factor to their heart disease risk, not so much the endurance training itself.

    What do you guys think about my take on this? Mark, do you want to throw in your two cents here, as I you know are well-acquainted with my story?

    Nick Laszlo wrote on July 9th, 2013
    • I’m looking forward to any answer about this! I did not know about the Kenyan jogging style, for one. And it’s way true about the excessive carb intake. I’ve been a very good runner for over 33 years, and most of those were high carb. I stopped running my 5.5 miles/per day a year and a half ago and miraculously stopped having chronic colds and bronchitis. Now I catch NOTHING the rest of the office catches. But I still enjoy an occasional longer run with a friend, and still place high in races using sprints and lots of walking instead.

      Joy Beer wrote on July 9th, 2013
  2. I used to run cross country and track in college and was definitely the leanest when I was training 60 miles a week (even on a grain based diet). Its hard to quit chronic cardio because I’ve never had such a rush as breaking 18 for the 5k, or running a 10k at 6 minute miles. I may be ‘healthier’ now but I just feel fat and slow. Anyone else feel like this.

    irunprimal wrote on July 9th, 2013
    • I know people who complain about feeling fat and slow when they’ve stopped endurance exercise.

      To me, the focus of this post and their talks about is “the rush”. That’s endorphin addiction, buried in random time tracking (minute/miles) and body image.

      An addiction that requires running miles a week is probably better than many others I can think of, but it’s an addiction none the less.

      Truly appreciating what your other appendages are capable of might help ease the body image problem. Visit a nursing home and then feel the “rush” of taking a walk. Garden. Make a sculpture. Squat. Try a pull up or two. There’s an amazing amount your body can do when it’s not trying to cover for the damage caused by too much exercise. Good luck. :)

      Amy wrote on July 9th, 2013
  3. Mark’s one of my heroes today in his late 50’s. I’m 54 and here’s one of my heroes from back in the day: Gary Player. He was a proponent of weight training and exercise before Tiger was even born. See what we’re capable of in our 70’s, the new 40!

    Jeff F. wrote on July 9th, 2013
    • Thanks for the link Jeff. I love Gary Player. That man looks fantastic at 77.

      Nocona wrote on July 9th, 2013
  4. I was just discussing with a critical care MD at work the other day the mounting body of evidence supporting increased mortality from endurance exercise. Right now it’s looking like anyone who logs around over 30 miles a week is doing more harm than good.

    And a. fib. is no good either. With the lack of turbulence in the heart from ineffective heart contractions it makes your blood easier to clot and is one of the biggest risk factors for having a stroke. Once in a. fib. it’s likely you’ll have to be on blood thinners like aspirin, plavix, or coumadin. And that presents its on health issues as well…

    Matt wrote on July 9th, 2013
  5. I am a former Cross Fitter and so glad I quit. I follow Rusty of and it’s made all the difference. I feel like I am finally losing fat after getting bigger and being constantly swollen at CrossFit. As a woman, that was hardly the way I wanted to look. Weights and HIIT training done separately several times a week plus playing around with diet, has bee a revelation.

    Rebecca wrote on July 9th, 2013
  6. If only I didn’t have this bucket list goal of a sub 3 hour marathon I could give up these 70 mile weeks with speedwork. Yes – resistance training and MDA eating (but you gotta eat carbs with 70 miles/week too). I’m 52 and close to my time goal – and I swear once I achieve that i’ll back off..well…I’m planning on it anyway. One confession too – had mild AF last year.

    Mark Kelley wrote on July 9th, 2013
    • This paragraph is cardio (endorphin) addiction in a nutshell. Is continuing to damage your heart *really* worth a sub 3 hour marathon? Isn’t your life worth something more than a time on a clock and short lived rush?

      Amy wrote on July 9th, 2013
      • Mr. Kelley, give it a rest. You are a beautiful human and OK the way you are…

        Nocona wrote on July 9th, 2013
  7. I haven’t been to the gym since summer began! My two exercise buddies are ages 10 and 8. So far, we’ve done crossfit kids (so fun, but not overwhelming), played tennis, completed our own kid’s tri (50 swim, 1 mile bike, .5 mile run), taken “long” bike rides ( 5 miles), scooter rides (4 miles), water-gun freeze tag, playground tag, had a balance day (stilts, pogo stick, skateboard and slackline), sprints on the track, and hiked to the river where we went tubing for 1/4 mile and repeated. Oh, and sometimes we play at the pool (I swim laps during the break). Every day is fun, not a workout. I make sure I get in some strength training if one of our activities doesn’t cover it, but short and heavy. Stop worrying about getting a “workout” and go have some fun.

    Kim wrote on July 9th, 2013
  8. While no one will ever accuse me of overtraining, I’m a 43 y.o. Female, 80% primal for 3 or so years, who spends about 6 minutes doing hill sprints, 3x a week. Add in a little gardening, the occasional walk or hike, and I look and feel great. Since I’m vacationing at the beach this week, the beach sprints are absolutely super-fun. I try the occasional push-up, and sadly, can rarely manage more than one – I admit that a little more body weight exercise would take care of that. But honestly, there’s never been an easier way to stay relatively bikini-ready.

    Lee wrote on July 9th, 2013
  9. I’m still allowed to run the Boilermaker 15K this weekend, right?

    It’ll be my… 17th? (And maybe my first one at a non-obese BMI.) I trained as a careful slow fat person. My pace is ~11 minute miles. But I still have all my original joints!

    A primal-curious friend asked me how I justify my running in light of your concerns over chronic cardio. I theorized that I probably run too slow for it to count. Would that be a fair assessment?

    Julia wrote on July 9th, 2013
  10. I was a very competitive soccer player all my life (22yrs playing). I played in college, olympic development program, and professional. I loved every bit of it and would never regret one second of it. I didnt do it for the medal i did it because i loved it. I think a big problem athletes have is that many of us are never taught anything about health and nutrition. We play to the max but dont have the proper nutrition to rebuild. MY coaches only ever taught me how to play but not how to eat or take supplements. We are pushed and pushed then taught to push even harder. In college for two weeks we practiced twice a day. Then we’d go to the cafeteria for pizza and cookies and grape juice. There was no rebuild strategy! And we were actually taught not to listen to our bodies. Well that being said i believe with the proper education we can safely play the sports we love. There is a spiritual aspect to the love of a game that i think not everyone can understand. I wish i had the knowledge about healing i do now but im glad that i can atleast use it to help young athletes. Reading this seems like its trying to scare people. My heart is fine and i have many tests toshow how healthy i am. I guess the love i have for soccer made happy cells.

    kristine wrote on July 9th, 2013
  11. Hi, Mark, or anyone else, please can you tell me what kind of Resting Heart Rate we should be aiming for then?
    And what kind of significance it holds regarding health.

    It’s just we are conventionally told that higher resting heart rate / pulse [above 70 say] is bad and lower resting heart rate / pulse is good [say below 70].

    It seems the way to really lower your Resting Heart Rate is through Chronic Cardio. If you look at different kinds of athletes those in more power/speed related sports/events tend to have higher Resting Heart Rates than those in the more cardio related sports – marathons, Tour cycling etc.

    One more thing. What does Chronic Cardio being bad mean for athletes that require it for their training? Is it just part of the “sacrifice” for success [A necessary evil say] or is there somehow another way to train for long distance events etc?

    Humatarian wrote on July 9th, 2013
    • Disagree. I’m 57 and I have a resting heart rate of an avg. of 50 bpm. I sprint once a week for 20 minutes. Do two 25 minute bodyweight exercises. I do a few meandering walks at an average pace around the neighborhood. That’s only 70 minutes a week of pushing it.

      Nocona wrote on July 9th, 2013
  12. Surely there is a difference between endurance athletes who eat traditional health junk fare and those that eat whole foods and eat plenty of fats. We need a study depicting the latter group.

    lisa wrote on July 9th, 2013
    • Why?

      A human body is not a machine. We have limits, we wear down and need to rest and rebuild. A perfect diet will not overcome constantly pushing a body to it’s outer limits and especially the heart, as Mark noted.

      If you’re going pro for a short time, I understand the training. If you love a sport, I get it, but I tend to think you’d want to cut back so you don’t have a crappy 5th, 6th, 7th and 8th decade. It turns out the fun factor is also the health factor, too. :(

      Amy wrote on July 9th, 2013
  13. I spoke at AHS12 about matching a paleo/primal framework to endurance training, based on recent sport science rather than just so stories, which ended with a very familiar slide for Mark.

    Jamie Scott wrote on July 9th, 2013
  14. Good read I hate cardio anyway

    Jackie wrote on July 9th, 2013
  15. I play soccer (actually futsal) two times a week for 1 hour and a half in an intense way (without even thinking because it’s so good), with a lot of intense bursts. It’s really tiring and the other day I do no exercise (a bit of walking going home). I try to do strenght training twice a week too, and nothing more. Maybe I’m overdoing it? But it’s so good, I don’t wanna stop :-(

    Ezer wrote on July 9th, 2013
    • I played yesterday and it seems that I’m not overdoing it, because it’s more like walk a little / sprint like crazy / kick the ball / stop / run to the initial position. And I actually feel great after the game and the day after.

      Ezer wrote on July 11th, 2013
  16. While healing from concussion, one of the limitations I had when it came to returning to exercise was a heart-rate cap. I could go for a certain period of time at a predetermined heart rate. For a period of time, this was 145BPM for 40 minutes. I would do this 6 times a week, and it actually hurt my head quite a bit – even though I would say that I was okay. Last summer, I decided I was done with the pain and the stagnant weight loss, and I just started walking outside every day. I walked for about an hour. Suddenly, my weight dropped, I felt healthy and my head was finally clear, and I came back into balance. When my clients ask me now, I always advise against chronic cardio, though they can’t seem to get past the CW about it. Someday.

    Mandy wrote on July 9th, 2013
  17. Yes despite much evidence to the contrary, it’s hard to skew my mind towards the fact that chronic cardio doesnt achieve as much weight loss as interval training but I am getting there!

    Mike Greenwich wrote on July 9th, 2013
    • Oh you’ll get there. Just do it.

      Nocona wrote on July 9th, 2013
  18. I’d rather stab myself in the eye than spend my time in the gym. My trail runs are the most therapeutic and healthy (mentally at least) thing I do for myself. I guess I will die any second from all my “chronic cardio” (this is not what Mark is suggesting but how many commenters seem to interpret this post which is silly).

    Danni wrote on July 9th, 2013
  19. Chris from the Extreme Weight Loss TV show just told the contestant, “This is a marathon, not a sprint,” while he was chastising her for dropping down to only 400 calories per day and was snacking on edemame. Sad :(

    Aimee wrote on July 9th, 2013
  20. I started distance running in 1976. I was a smoker and heavy beer drinker in college. I threw it all away and got in shape or so I thought. Now at 58 I’m looking at a hip replacement in 1-3 years. I constantly have knee, back, and hip pain. Oh if I had only known then what I know now. I’m now on the Paleo diet. I sprint on a stationary bike and lift twice a week. I’m in better shape at 58 than I was at 28. My blood pressure is lower and when I’m not feeling too much joint paint I’m on top of the world. Keep up the much needed advice Mark.
    Jeff Taylor

    Jeff Taylor wrote on July 9th, 2013
  21. I suppose I’m a bit confused. Forgive me if this will sound naive, but I thought that the point of training and exercise was to get oneself to higher level of ability and skill. If you are, for example, training for a, you are increasing your bodies ability to do more than it could before. And if your body can comfortably do more than before, isn’t that what good health is all about?

    Of course, I’m no marathoner, I don’t have time for that sort of thing. But I always assumed that if you COULD run a marathon, you would be in better health than someone who could not. In my mind, greater ability equals better health, equals more comfort and happiness and satisfaction, etc. What am I missing here?

    Kalvyn wrote on July 9th, 2013
    • Oops. Meant to write ‘training for a triathlon. Lost in spell check…

      Kalvyn wrote on July 10th, 2013
    • That’s the rub: health and fitness are two separate things. You can be very fit yet unhealthy, or very healthy yet unfit. One is from diet, the other from exercise. The old (1960s-to-present) wisdom, dating from the ‘Aerobics’ book and revolution, was that marathoners would live forever and could never get heart disease. Completely wrong.

      BillP wrote on July 10th, 2013
  22. Hi Mark,

    I thought arrhythmia was caused by doing too much HIIT rather than chronic cardio?

    Speaking from an endurance athlete’s point of view, doing long course races or running long distance is actually addicting. It’s not so much about the pain as HIIT is 1000x more painful! But it’s the trance-like state after running how-many-miles that got us hooked. Of course, we often find ourselves tired, cranky and hungry as if we had constant PMS.

    I’m honestly torn between love and hate for chronic cardio but on the other hand, I’d love to find the proper nutrition that supports endurance training and optimum recovery. Is there a chance you can delve into details about the subject in the future posts?


    Joey wrote on July 10th, 2013
  23. I run frequently, minimum of 5 times a week, for about 2 hours at a time with something longer on the weekend, and have done for a while now. Occassionally, like today infact, I woke up later than usual, tired and have decided instead to rest. It’s bound to happen once in a while. Point being, I wouldnt be able to keep my routine if I pushed myself hard every day. I run when I feel good, hike up hills I can’t comfortably run up, and generally love being outside running, especially early in the morning when the sun rises. I feel the most human I ever feel when I run trails. From what i’ve read on this site, I have concluded the secret of ‘primal’ running is all or (almost) nothing. Sprint, or go easy. Nothing in-between. The secret to ANY running regime? More base, less speed!

    Jenry Hennings wrote on July 10th, 2013
  24. Hi,

    Would about half of an hour of interval training style jump roping daily be considered excessive. I can’t run very far or well, because my knee kills me, but somehow the jump rope doesn’t hurt at all. And, by interval training style jump roping I mean switching between jumping as hard and fast as I can to a super easy jog style jumping to catch my breath, all the while while switching between leading feet, or jumping with both, and other variations. Thanks for the input!

    miķelis wrote on July 10th, 2013
    • My apologies, that first sentences was meant to have been a question, with a question mark. :D:D:D

      miķelis wrote on July 10th, 2013
  25. Well, now I’m thoroughly confused. I just finished Christopher McDougall’s book last night “Born to Run” and found it inspiring and made me want to pick a marathon to train for. Although I don’t recall the book addressing heart issues it did address other common injuries and suggested the solution was getting rid of the overly cushioned running shoes. It also suggested we evolved as humans because we were adept at endurance runs in order to practice “persistence hunting”. How could we have evolved based on our capacity for endurance but have flawed hearts making endurance too risky? Maybe the heart issues aren’t because of chronic cardio alone but a combination of chronic cardio if it’s coupled with the modern SAD diet or some other factor?

    sarah wrote on July 10th, 2013
  26. I wish the title of this was “chronic ANAEROBIC cardio”I have been a big fan of Dr Phil Maffetone’s approach and I embrace my HR monitor I use for every run. It irks me when I hear folks talk about how fast or long they ran a race without any care of their heart rate. It is essential information. The aerobic system in our bodies is very efficient and can grow to be highly efficient but not when anarobic activity is the norm! I am sure there is a study out there which has looked at the health effects of aerobic cardio over the long term but I haven’t seen it. Too many times those who report this lump anaerobic and aerobic together. They are very very different. And the impact on the heart in the long term is also. Grok didn’t have one but we all need to have one handy if we want to know which system we are using and I sure think we all could and should have much more deeply developed aerobic systems before we take on a lot of anaerobic excercise:)

    Dave W wrote on July 10th, 2013
  27. The article implies running/cardio causes Atherosclerosis – not true!! But running masks the symptoms (as you point out) of a diet that causes Atherosclerosis. There is a widespread assumption among runners that they can eat anything, and many can because they don’t put on weight. But the internal damage from a bad diet isn’t caused by running any more than by weights/gym workouts. I have to say, I don’t understand why gym rats are so down on people who like to run. It is a mystery to me why they even care.

    Erik M. wrote on July 10th, 2013
  28. Great article…I have a question, though.

    Monday – Friday, I walk 2.5 miles in the morning, between .5 and 1 mile while at work (walking to and from my car which I park .25 miles away from my office), and then walk for about 5 miles in the evening. I mix in some more intense, but not that intense elliptical for 30-60 minutes at the gym. I also do some strength training in the morning for 30 minutes.

    If I am tired, I’ll just rest in the evenings. I usually rest on Sundays. Mondays I get out for 10 miles with no strength training.

    Is this considered over doing it according to the studies referenced?

    david wrote on July 10th, 2013
  29. I’m all for n=1 and followed the primal diet since end of February. I’ve lost 14lbs from a healthy weight of 159lbs to 144lbs standing at 5’11”. I ran a marathon in June. My next n=1 is the maffetone heart rate method whereby I will not go above a heart rate of 148 until I have an aerobic base built up. I don’t consider this “chronic cardio” -I honestly think Grok and his relatives spent their lives roaming the plains of Africa looking for food and hunting animals and had massive endurance bases. I agree with the primal diet and once your aerobic base is built I believe in sprinting and lifting heavy things butI think we should be cautious about how we advise people how to or how not to exercise. Overtraining is a result of people thinking they are doing chronic cardio but are actually edging over into anaerobic training at all times during their training sessions. Read Maffetones stuff it makes as much sense as the Primal diet and he advocates the low carb diet too.

    Jencossy wrote on July 10th, 2013
    • I bet most of the folks who ran that marathon with you had no idea what their HR was and didn’t care to know. It is essential. Good for you!! Maffetone, Sock Doc and Dr Mark C all are big proponents of getting the aerobic base fully formed and that takes much longer than most folks want to invest. That’s why I worry for folks who are doing to much HIIT stuff right now NOT knowing about the risks and without solid aerobic preparation. Jen what is the sustained pace you are running at that HR of 148 and where was it before when you began? Thanks

      Dave W wrote on July 10th, 2013
  30. And then there’s always rhabdo to worry about…

    Dan wrote on July 10th, 2013
  31. Mark,
    I have a treadmill desk and I walk on it as I surf the net and stuff. I walk at about 2 to 2.5 mph. I do this because sitting is supposed to be terrible for you.

    Would this qualify as “chronic cardio” and be destructive?

    My understanding is that the human being was supposed to walk. A lot.

    Ari Mendelson wrote on July 10th, 2013
  32. Okay, I have a question. I just happened upon this website via Facebook and read all the comments thus far. Really interesting.

    I’ve had a weight problem all my life and have done all the diets and fell off all the wagons. Been in the gym and out of the gym though mostly out. I got laid off from my gov’t job back in February and since I have nothing to do besides look for work I figured it’d be a good time to work on my fitness. Well for the past 13 weeks I’ve been swimming a half mile 5x a week. I was doing mostly backstroke so it would take me an hour. After my hour of swimming I do work with the water weights and with a resistance band. Last week I started doing breaststroke and freestyle and found that the half mile only took me a half hour so I went ahead and started doing a full mile which takes an hour with those strokes as well as 30-40 minutes of water weights and resistance band work after my laps. Is this chronic cardio?

    I REALLY enjoy swimming and have never swam for fitness before. I never knew that swimming burns SO many calories! So far I have lost 12 lbs but tons of inches! I didn’t measure in the beginning but I’ve lost 2 sizes in my shirts and 1 size in my pants! Again I’m enjoying it immensely but am wondering since reading this if I am doing chronic cardio?

    Laura wrote on July 10th, 2013

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