Dear Mark: Chronic Cardio

Dear Mark,

I’m still having a hard time understanding what “chronic high level training” is, exactly. How much is too much? Is there a heart rate zone you guys can give me? A time limit? Am I overthinking this??

Thanks, Charlotte, for posting this question last week. As is so often the case, another MDA reader (hats off to you, Mike OD!) offered great advice. We thought the question was well worth revisiting. First off, let’s investigate the concept of chronic cardio. Intense cardio as we commonly think of it today means long stretches at a sustained heart rate in the 80+% range.

The fact is, our hunter-gatherer ancestors didn’t ramp up their heart rates significantly for over an hour every day, and I don’t think we should either. They walked at a very low level of exertion, burning almost entirely stored fats. Once you get into the zones where less fat is burned and where there’s a big dependency on glucose to fuel muscles, your body goes into a less efficient mode of fuel oxidation. There are biochemical costs associated with this shift. Your muscles and liver can only hold 500-600 grams of precious glycogen (stored glucose) at any one time, which means about 2 hours’ worth for the best trained individuals and less for most people. That means that to come back and work out hard the next day requires at least 600 more grams of carbs every day. That’s just too much glucose and insulin to deal with every day.

I don’t recommend pushing this limit or even approaching it. Why bother? This kind of training (and diet) raises cortisol levels, increases oxidative damage, systemic inflammation, depresses the immune system and decreases fat metabolism. About the only thing good it does is improve cardiac muscle strength – and even then you get too the point of diminishing returns fairly quickly.

As you know, I recommend a different approach that more accurately mirrors what we evolved doing. In those simpler (but not really “good old”), primal times, we spent several hours a day engaged in low level activity. A few times a week, caveman/woman life required brief spurts in high intensity anaerobic mode to run from various predators, hunt down dinner, engage in “play” etc. Each of these modes resulted in its own unique and very positive growth response.

This pattern, for most of us, isn’t easily replicated as a result of our busy lives. Instead, I suggest anywhere from 30 minutes to an hour of low to moderate level aerobic movement such as walking briskly, hiking, cycling, etc. It doesn’t need to be every day, but at least a few times a week is important. The goal during these sessions is to maintain the zone that burns mostly fat. For very fit people, this could be as high as 70-80% of your maximum heart rate, but we’re really talking 60-70% for most people. The benefits of exercising at this zone are numerous and the risks minimal. It’s the ideal level of activity for decreasing body fat, increasing the capillary network, and for lowering blood pressure and reducing risk for degenerative diseases, including heart disease.

Add to this routine a few anaerobic, “interval” workouts once or twice a week. Weight-bearing, anaerobic bursts are the best training for building muscle, and lean muscle mass is critical to health. It also increases your aerobic capacity, natural growth hormone production and insulin sensitivity.

Traditional running sprints are one option, but we presented several others last month for your perusal. Put your all into it for 20-40 seconds and then rest for two minutes or so between “sets.” You can start out with three or four bursts and work your way up to as much as eight. As always, get in some warm up time and stretches afterward. It’s no fun pulling a muscle.

Finally, working all muscle groups through dynamic strength-training sessions (ie: lifting weights) a few times a week helps further build and maintain muscle mass, insulin sensitivity and growth hormone release.

Finally, let me add that I’m not trying to squash anyone’s passion for competing. As a former competitor myself, I totally “get” the drive to compete. Do I think that mode of existence is healthy, particularly in the long run? Not really, but I still understand what brings people to it. I simply want to convey that certain and sometimes significant health compromises are inherent to competition training. If anti-aging, longevity and robust excellent health are your primary goals, high-level training isn’t the best way to achieve them.

Now, for those who aren’t into the competition mission, you have the advantage of making your fitness routine and health about ideal balance. And I’m a true believer in achieving the balance that allows people to live the longest, healthiest lives possible. Thanks for your questions, and keep them coming!

Abraaj Flickr Photo (CC)

Further Reading:

My Weekly Workout Routine

Anaerobic Exercise HGH Link

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About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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67 thoughts on “Dear Mark: Chronic Cardio”

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  1. I have discovered that if I have to make exercise a separate activity, I won’t do it. It has to be a natural part of my life.

    What do you think of this? I think it seems kind of like what Grok would do, even if the activities a modern person needs to do are a bit different.

    * Walk 2 to 4 miles a day. (I don’t have a car, so I already do this.)
    * Carry a load during most walks (groceries, laptop – Grok probably carried an antelope or something).
    * Sweep and mop my 1200 sq foot house twice a week. After completing each room, do 20 to 40 seconds of very fast jumping jacks, then go to the next room and sweep and mop (low intensity), then more jacks. Plus, it will get rid of various cat messes (added bonus).
    * Two or three times a week, do as many pushups and squats as I can without hurting my joints. Maybe use some dumbbells with the squats as my legs get stronger.

    1. It’s pointless and stupid unless you want to stay the same as you are.

    2. I think it’s a great idea, despite what the previous guy said. It’s been 5 years since you posted this, so now the obvious question is: did it work for you?

    3. I read that when they found that Ice Man of the Alps back in the 90s, they claimed that he carried a bow that weighed like over 40 lbs or something. I guess even the Ice man was power full enough to carry such a heavy piece of wood probably every place he walked to. Maybe human genetics leans towards muscle mass and strength like most primates vs long endurance body types of gazelles and cheetahs.

      1. That’s 40 lbs draw weight, and it’s an estimation. The bow was actually an unfinished staff he was working on. It was made of yew, as they have been for thousands of years, and thus wouldn’t weigh any more than a modern longbow made with traditional materials. A few pounds.

      2. OK, so I looked at the 2013 to make sure I wasn’t replying to a five year old comment, but missed noticing the day. Ok, that happens and we all get got now and again and get over it and get on with our lives, but what really embaresses me is not noticing the “tell” about the gazelles and cheetahs.

        I really need to get the hell away from the dullards for a while. They seem to be rubbing off on me. Ewwwwww!

  2. hi,
    this is the first time I’m leaving a comment, maybe I should’ve before because I guess it’s always nice to hear how good of a job everybody’s doing here at MDA.
    the article says that training the the 60-70% max heart rate range is (for most people) “the ideal level of activity for decreasing body fat”. I’ve read and heard this countless times before, in “fitness-magazines” that also talk about how carbohydrates are healthy as well as from people that weigh double their optimal weight. However, each time I hear it or someone tells me I get a bit aggrevated. I’m german, and have read an excellent german article about how this argument just doesnt make sense, but I guess it’s no use posting it here.
    But the idea is that when driving a car at a high speed you reach your destination faster and you will need more fuel compared to when driving slowly. Likewise, doesnt the body burn a lot more energy when you engage in sprints or similar interval training that I usually find being promoted here? Of course the burned carbs will be replaced from the fat storage. Hasn’t this kind of exercise also been shown to have strong post-workout engergy-burning effects?

    I have the impression that a line like this is all some people are looking for to go jogging at sub-snail speeds, claiming that it’s the most efficient way for them to loose fat, when they might be better off doing a few sets of pushups, jumping jacks, or similar calisthenics – basically just what is being promoted here besides running at 60-70% max heart rate.
    So, my point is that although I’m sure Mark still knows a bit more than I do about this topic and always gives great advice, this one argument for running is one that I simply feel gives some people a very wrong idea of what they should be doing. Instead, regular low intensity activity could be achieved by taking riding the bike to work or when shopping for groceries (which I both do myself), and even doing work around the house (as mentioned by Migraineur).
    Sorry for writing so much. Thx if you read it ,)

  3. this sounds like a great plan to keep but i have a question…

    I’ve been underweight for a while and trying to gain a little more until i stop living so tired. ive been told to absolutely abstain from exercise but this doesnt seem right?
    what should i do for diet/exercising?
    [without killing myself lol]

  4. can’t edit, so I’ll have to post another comment:
    I think I meant annoyed, not aggrevated, which isnt even a word. sorry bout that and the other typos.

  5. Vasco,

    I assure you that you are not alone–there seems to be some considerable debate over the notion of a “fat-burning zone” and the best methods of exercise to promote the use of fat reserves as fuel. And I wonder about the substitution of the 60-70% of max heart rate exercise for the hours of wandering the plains by our primal ancestors. That being said, I still believe Mark is outlining a good program to follow and his lower-effort exercise doesn’t have to be jogging/running. I find that I can go on a bike ride without having to push too hard and maintain a heart rate in that zone, and I can do it for an hour or more without killing myself. But I do workouts throughout the week that are more in the interval mode using a stationary bike or a rowing machine. My resistance work provides some of the same effort because I tend to do whole body exercises that tax the cardio system while providing strength training at the same time.

    I actually have a plan to do a better job of simulating our primal ancestors. I figure if I spend four or so hours every day on the golf course carrying my own clubs, that would do the trick. And as Mark pointed out in a comment on Art’s blog, if you spend some time searching for and collecting golf balls, then you are realy emulating the hunter-gatherer!! The only roadblock is figuring out how to fit that in and earn a paycheck at the same time!!! 🙂

  6. For what it’s worth……
    My workout this morning lasted approx 20 minutes.
    That included a 3 min. warm up and 5 min. of stretching at the end.
    Fast, furious and heavy. It left me feeling energised and ready to take on the day.
    The trainers always look at me when I walk out, I can feel them thinking….”well he obviously doesn’t know what he’s doing”


  7. LOL!! My workouts have evolved based on the sample workouts you sent me, Art’s heirarchal sets, and some of the stuff from Crossfit. No routine, never boring, quick!! 🙂

  8. I just wanna mention that I do mostly crossfit-type workouts myself, many of which I have from ross enamaits books, if anyone knows him. fun and quick workouts too. and I do almost all of my workouts in the 3.5*3.5meters room that I live in (I’m german army) (of course not the sprint work)
    I love Art’s blog, but I dont see him so much as an authority on actual workouts as on the ideas behind primal/evolutionary fitness.

  9. I have a very seldom used formal living room that I would love to turn into a crossfit-style gym. I might have a tough time selling that to the wife but then maybe not (she does 4×15 pullups, dips, and pushups three times a week). By the way, I lived in Berlin for six years and I really miss cycling and running in the Gruenewald–especially mountain biking in the winter (followed by a cup of Gleuhwein!) 🙂

  10. Wow…thanks for the gold star..I put it on my fridge! Ha.

    In response to anything that follows “So I was reading some fitness magazines….”, everything after that is mostly outdated and wrong.

    Fat burning is an all day event dictated by hormones. So how much fat one burns during exercise is really not important or accurate. Real success from people are ones that made more changes to healthy lifestyles (walking, riding bike, playing sports) than those stuck on treadmills at the gym….as you will see the same people year after year on the same treadmills. 15 min of shorter higher intensity training will burn 4-5x more fat all day long than 40min on the treadmill….because of the hormonal release of GH and other muscle sparing/fat burning processes.

    Fitness magazines are in business for one reason…their advice is not getting many people results…cause if it did, why would you keep buying them??

  11. >>15 min of shorter higher intensity training will burn 4-5x more fat all day long than 40min on the treadmill<<

    I want to believe this so let me pretend I’m Gary Taubes AND I’m from Missouri: Show me! Got a cite for that of a real scientific study? Without it “I read in a fitness magazine” = “I read on a blog.” 🙂

  12. Wow, thanks for the explanation Mark! I really appreciate your advice (and everyone else’s tips and comments were interesting too). I’m a chronic overexerciser. I do at least 2 hours a day but sometimes 4-5. Since stumbling upon this blog though I’ve ramped it down a bit (not timewise but at least intesity wise!).

    I found it very interesting what you said about our glycogen stores only lasting about 2 hours. So when I “bonk” after a hard workout, am I simply feeling my glycogen run out?? And is that why I crave straight sugar when I get home? (Literally – I’ll eat a big spoonful of sugar. It’s like a compulsion. I simply must eat it or I feel like I’ll faint. I’ve tried subbing nuts or something healthier but sugar’s the only thing that will do it.)

    So if I cut the long/intense workouts, will my sugar cravings go away?

    This is so interesting!!
    Thanks everyone!

  13. I had this long response this morning that got lost when I tried to reply…on my own damn site!!

    Anyway, MikeOD is right. The fat-burning effect of exercise is minimal. In fact, doing more exercise usually only increases appetite as the body tries to overcompensate for the loss of energy. Unless you are an elite athlete or on a very strict calorie-controlled diet, exercising more probably won’t do much to help you burn fat effectively. Most recreational marathoners carry around an extra layer of bodyfat as their bodies hoard the fat stores and burn the carbs off. On the other hand, sprinters have very low body fat and do almost no traditional “cardio.”

    It all comes down to this: fat loss depends 80% on what and how you eat. Retrain your energy systems to burn fat and not glucose. Cutting out all simple carbs is the key. It’s about insulin management. If you can readjust the diet to encourage the body to burn fats, you won’t need to replenish lost glycogen every day. You’ll always burn fats and you’ll always have energy. The low level aerobic stuff becomes “filler”…so you only do it if it’s fun,like a hike or walk with friends or golf or mountain biking. The real muscle growth will come from the short anaerobic bursts like sprints, intervals or weight-training. I’ll do a piece on this later, but check out my friends at . They get more done in 20-30 minutes than most of the gym rats doing 90 minute weight sessions. And because it’s a “circuit training” concept, they get plenty of heart-training (cardio) as well. And growth hormone release and insulin sensitivity, and….you get the point.

  14. Dave C,

    Ask and ye shall receive. Reader Chris posted this on his blog today
    wherein he cites a study released today that shows that mice who lift weights burn more fat. Well, not exactly, but mice who developed more type2 fibers (the kind you get from lifting) burned more fat than mice with more type1 (slowtwitch – marathon) fibers. Granted, mice are not people, but this mouse model could help explain it all. Thanks, Chris.

  15. Mark – who mops twice a week who doesn’t have pets? Besides, wouldn’t that drive me over my intensity limit?

  16. Thanks for the link Mark. I subscribe to Chris’s blog but I can’t read it at work. For some reason our firewall thinks it has “malicious content.” You hiding secret messages in there, Chris?! 🙂

    This whole trip for me began with doing kettlebell workouts that fit in the Crossfit concept. And your “Case Against Cardio” sealed the deal! Like one of the trainers says in his signature on the kettlebell forum: “Train Like An Athlete…Not A Hamster!”

    Time to head out for some sprints on the beater bike!

  17. Nothing malicious that I am aware of. My work is like that too – things that seem totally innocuous are strangely blocked…other stuff gets through.

    Like the hamster line. I was watching my cousin’s kid doing his swimming training at the weekend – up and down the pool for long intervals – 90 minutes in total. They are great athletes, but it looked so boring and lacking in “fun” . When the kids let loose a bit and started fooling around, the coach told them off.

  18. Chris,

    I’ve been involved in age-group swimming for four years (I officiate both USA and high-school swimming). I’m in awe of what these kids go through. I’ve spent many hours and many miles running and cycling, but at least I had some variety in what I was looking at while doing so. Swimmers spend hours looking at a black line. My club tries to let the kids have some fun along with the hard work but make no mistake…it is hard work.

  19. Good stuff here.

    Dave C – Damn you got me (hiding Muscle Media 2000). Ha. Anyways, can’t find any studies off hand, but I’ll ship some of my clients who have lost fat and look great. It’s through 10 years of observation and on hand training with people that I have come to my philosophy on training. Lots of good research coming out nowadays to prove it all, but I don’t need a study to back up what I already know. Developing the right kind of muscle fibers and keeping their nutrition on track seemed to get 95% of their results (even without so called cardio).

    I always liked Alwyn Cosgrove’s summation as well:

    I’ve done too many body fat tests on skinny-fat joggers…and they are all usually over 25% BF.

  20. Mike,

    No “gotcha” intended—just was curious what the science was behind the claims. I’m in your camp–I’ve bought in since I first read Mark’s Case Against Cardio.

    BTW, enjoyed your input on diet-blog. I’m guessing several of us have very similar RSS lineups! 🙂

  21. OH…and one more thing…fitness magazines aren’t even close to dispensing worthless advice when compared to golf mags!!! 🙂

  22. >>Most recreational marathoners carry around an extra layer of bodyfat as their bodies hoard the fat stores and burn the carbs off.

    Uh… ever been to a marathon expo? Most marathoners are pretty damn thin. And most runners know that yeah, you don’t run at 80% of your maximum heart rate two days in a row. That’s a surefire way to burn out. Easy/hard/easy/hard.

    Anyone who is exercising more than five or six hours a week and claims to be doing it for the health benefits is probably lying anyway.

  23. Derek,

    I used to be a marathoner, so I went to lots of expos. MOst recreational runners are what we call around here “skinny fat.” They may look thin, but that’s because they have less muscle mass than the average person. Conversely, they do carry a few extra % of body fat, but you just don’t notice it.

    Also, I would bet many runners train at 80% max HR a lot. For a 40-yr-old who’s max is 180, that means only 144 BPM. That’s pretty “easy” to maintain for over an hour a day for someone training to run a 3:15 marathon.

  24. Also, I would bet many runners train at 80% max HR a lot. For a 40-yr-old who’s max is 180, that means only 144 BPM. That’s pretty “easy” to maintain for over an hour a day for someone training to run a 3:15 marathon.

    You are probably right about that, but that’s like saying that you shouldn’t do any bicep curls because your muscles need 48 hours to recover between workouts. Well, only do your bicep curls on alternative days!

    Anyone who’s serious about running should get a heart rate monitor and be sure to keep their HR under 70% of max on easy days and 85% or over on training days. The under is frustratingly slow at first, but it gets better …

    I’ve measured anyone’s body fat at an expo, but most runners I know, know they should be working out with weights as well. (And I’d def. recommend them Crossfit-style workouts as an alternative to traditional lifting … I’m at 8% body fat, if you believe my bathroom BF monitor). Don’t know if you saw Josh Cox on the cover of Runner’s World, but he had some pretty ripped abs there…

    I’d love to take my running club through a Crossfit workout and see how they do … and then my Crossfit gang through one of my running club’s speedwork sessions…

  25. Derek,

    Cox is clearly ripped and it’s the intensity of his hard training days that keeps him that way. I agree that most elites have low body fat, but most age-group run-only runners have higher body fat than you’d expect.

    I also agree it would be fun to put an elite marathoner through crossfit programs. The danger of specialization in distance running is that you lose almost every other aspect of total fitness (strength, power, flexibility, speed, agility, etc)

  26. This is the 1st time I’ve stumbled upon this website. I love working out and do it often enough so that at the end of the month, I make sure I have more “workout days” than “rest days”. Usually I do 45-60 minutes of cardio, abs and use weights on-and-off. I have two questions:

    1) You always hear that “women won’t bulk up when using weights because they don’t have enough testosterone”– I know that there are certain excercises I can’t do if I want my jeans to fit. I am the opposite of “manley” but have played sports all my life and develop muscle very easily. I stick to a healthy diet the majority of the time but also allow myself to enjoy my favorite foods, just not everyday. I even find that running too often causes my legs to bulk up. I’ve always hated having muscular legs and would like ideas of workouts to slim them down, not bulk them up. Any ideas as to why this happens and how to avoid it?

    2) I LOVE cardio. Is this article telling me that doing cardio won’t help me maintain my weight because it’s not actually effective at burning fat? I rely on cardio to get rid of extra calories and always assume that I need to do more & more to lose weight. Since I started running and working out hard, I feel sluggish and bloated if I don’t do cardio for a few days. What’s the deal here?

  27. Amelia,

    1) Running is usually known for slimming legs down more than any other cardio exercise. If that’s not the case with you and/or you don’t want “muscular” legs, the best bet is swimming.

    2) Cardio does burn some calories (and running is best at it) but it’s the KIND of fuel that it burns that we talk about here. I’m not against cardio per se…just doing over an hour for several sessions a week. My ideal regimen for health would be going for 2 hour hikes (low level aerobic) and then 2 sprint sessions a week (to promote fat-burning and growth hormone)

    PS why you opposed to musclular anything on women? it’s the new look and VERY healthy.

  28. I’m a CrossFit affiliate owner (CF Hampton Roads in Yorktown VA). Been CFing for 5 yrs. I’m also a former tri and marathoner and MDA fanatic. The PB & MDA have become two of my primary blog sources. Robb Wolf ( (work friendly)is CrossFit’s lead Nutrition “guru” and is an excellent source for Evolutionary nutrition and fitness discussions including gluten/lectin/autoimmune connections and the whole insulin gammit.

    CrossFit’s efficacy is founded in the same principles that MDA preaches: all the good things from fintess come with intensity–short durations of high intensity to be specific. While CrossFit quantifies its gains as increased work capacity (in a broad range of movment and time domains…aka not specializing), the outcome is the same as Mark’s recommendations: overall health markers improve…drastically and consistently. To a CrossFitter, burning the fat is a positive byproduct of addressing nutrition and working HARD for short periods. Does it have to be labeled CrossFit? Absolutely NOT, but it is a tight knit community much like PBers.

    I’m also in the military…the USAF, where the emphasis of PT is placed on running a 1.5 mile test. When it comes down to combat, health or my neighbor helping we shovel mulch or pulling me and my family from a burning house, I want the neighbor who can lift heavy things and move them quickly…that’s what life demands of all of us and has for eons IT’S ALL PRIMAL!!! I’d hate to have a professional marathoner next door when I need help moving furniture. My family and my gym train FOR LIFE. GROK ON!!!

    1. But he could move stuff all day long, when your muscles give out after an hour. What isn’t to like about that?

  29. Hi Mark,

    I have recently discovered the site and it makes very compelling reading. I might just get a copy of your book.

    One thing on the cardio.
    I have recently watched some of a british (BBC) documentary of name that escapes me.

    It was about how the human race evolved and travelled from africa to populate the world.

    As part, the documentary went to east africa and spent time with north east african hunter gatherer tribes. They were trackers and when they picked up a trail they ran at a reasonable pace for sometimes an hour or more.

    These people really reminded me of the likes of Bekele or Heile Gebreselasie in body shape. They were capable of long distance running, with naturally efficient stride not too far from Pace or chi running.

    What strikes me is that this seems to be a bit at odds with your postulation of what would be the behavior of Grok.

    How would you reconcile this behavior?

    1. Cormac, I guarantee that they weren’t running at a high-end aerobic pace, but rather jogging with occasional bursts at a pace that would be considered “low level aerobic” pace similar to that which I espouse. Additionally, they don’t do this every day.

      1. I Think I get it.
        It was more like a long striding Jog, If I remember the name of the series I will let you know. It is interesting.

        Thanks Mark.

  30. Mark,
    I was curious as to what you thought of the relationship between VO2max and cardiovascular disease. Every percent increase in VO2max can greatly reduce the risk of cardiovascular disease, apparantly. Would an optimal VO2max be achieved with your recommended exercise? or do you think we’d all be quite comfortable, yet a greater risk of cardiovascular disease?
    Then again, this is with the general population, the carb crowd, so the primarily glycolytic energy system may play a role in offsetting the CV risk of all the carbs, which we don’t have to worry about. What do you think?

    1. Like everything else in life/science, this applies generally to a general population. Certainly, increasing VO2 Max in relatively sedentary people will confer a benefit up to a point. I say there may be a point beyond that where the work necessary to increase [email protected] stops producing health benefits.

      Don’t forget, you don’t need to do a ton of traditional cardio to increase VO2. Research shows that short, intense intervals increase VO2 substantially. I contend that following a movement (exercise) pattern of our ancestors (lots of low level and a few minutes of very high intensity) develops what we might call an “optimal” VO2 max. Optimal here means optimal for health and longevity. Specific endurance performance goals may require added VO2 manipualtion at the risk of decreasing health.

  31. How do you explain the tarahumara? A population in northern Mexico that bases its culture on running, they routinely run massive distances, putting marathon runners to shame. Their diet contains almost no meat, yet they appear to be some of the healthiest people around. The deaths that do occur seem to mostly be caused by infections and injuries.

  32. Dima, the Tarahumara have lots of health issues that seem to somehow be overlooked by those reporting on the running they do. I don’t think they put marathoners to shame since they don’t run very fast. (maybe as ultra runners they do). Running is/was a way of communication and transport in the desolate canyons in which they live. They show that humans CAN run, not that they SHOULD run. They do also tend to prove the notion that we should NOT be wearing high-tech shoes if we choose to run.

  33. Could you provide evidence for the health issues that these people have?

    1. Also, could you explain the runner’s high? Why would the body release a flood of endorphins after miles and miles of running, if primitive humans never had to undergo such activity.

  34. Another perspective you might not have considered: For me, endurance activities are a way to relax, to reboot my brain, to take time for myself. They are my “play”. I’m naturally high-strung with a busy schedule, and my long, slow runs and swims are time for me to unplug from the world and enjoy how well my body moves. I do also get that feeling from strength training, interval training and low level activities, which I do frequently. But I’m not giving up my endurance work. Even if it does shed a few years off my life (which I doubt), the joy and serenity it brings to my life is worth it.

  35. I am just beginning to look around on these blogs, I have been tossing around the ideas I’ve seen here and will probably begin implementing them more seriously over the next few days, this being said I am not really all that overweight, I am a bit, but I am losing, and pretty quickly NOT through the methods on this site. I am losing because I exercise constantly and I am just now not indulging myself constantly. The philosophy is what draws me more than anything, that the modern day body, like an animal, does exactly what it is told. Our instructions are what is lacking. I have always felt there was something odd about how the modern human lived. Why for example is it so painful to not eat for a day. What have we taught our bodies to expect? Obviously you all understand the philosophy and use it in your lives and I applaud you. I came here while looking at a CrossFit website and thought: “I’m glad someone took the instinct that I’ve felt and ran with it” This is great. My question is, as you mention before about competition, do you have any suggestions to someone who wants to follow your diet/philosophy but is more concerned with progressing at a competitive sport now, than overall longevity? I am not living up to some extreme where I want to get loaded up on steroids, I just like beating myself up with exercise and training but also want to implement as much of your plan as possible. The sport: Fencing. Thank you so much for your time.

  36. I’m curious, Mark, how do you reconcile your vision of “Grok” being a slow-moving, sometimes-sprinter with the persistence hunt? Clearly we were eating meat long before we had weapons and we had to catch it somehow.

  37. Hi, Neat post. There’s a problem along with your site in web explorer, could check this? IE still is the market leader and a good component of folks will leave out your wonderful writing due to this problem.

  38. This website might be useful if you want to check your heart rate online.

    Just tap the space bar whenever you feel the beat and it will tell you your BPM and calculate your training zone.

  39. I have a question regarding chronic cardio type training.

    I am contemplating a trip to Thailand in the next few months. My cousin and friends went to a Muay Thai training camp and trained with them. The thing is, the training is very intense, and it lasts several hours a day.

    Is there a way to prepare myself for this type of exercise? What can I do to reduce the stress/cortisol response, and keep my body from being depleted and then respiked with insulin?

    Thanks for any help!

  40. This is somewhat depressing to me. During the warmer months I like to do a 30 mile ride on both days of the weekend which takes me 1.5 hours per ride. I’ll have to dig out my HRM to see just how much I am pushing myself.

  41. Slaves eat grains.
    Slaves eat carb heavy diets to deal with the amount of work they have to do. Is it any wonder soccer moms and business men are running around like chickens with their heads cut off and chowing down on candy bars and carbs every five minutes?
    Examine your lifestyle: if you are having a hard time getting through your hectic workday without overeating carbohydrates, you are a slave. YOU ACTUALLY NEED TO EAT CARBS, OR YOUR BOSS-MASTER WILL NOT BE HAPPY.

  42. Hi Mark,
    I am 18 years old and have competed in middle distance events the last 2 years (Averaging 30-50km a week), but have recently quit endurance training due to low T levels. I still want to compete in athletics though- so do you think the typical training of a 400 metre runner would be classified as ‘chronic cardio’? Which athletic events do you think are ideal to still enjoy competing and training, albeit without producing too much stress?
    Thanks a lot, I love your blog,


  43. Why would anyone worry about getting too much exercise if they are having a blast and feeling great? I surf every day. Have been for over twenty years. Sessions average an hour and half in 52 degree water. Air is usually in the forties. When the water gets up into the high fifties and air warms a bit, two and three hour sessions are more frequent. Every other day I do a 10 minute planking routine and on alternate days I do a half hour or so of interval type training on my spin bike. I adjust this upward or downward depending on my energy levels. More hard surfing (my main priority) means backing off on bike and plank and vice versa. I can’t imagine not surfing ( about the most enjoyable/feel great thing in the world to me) to meet some assumed paleo level of activity. I don’t think that’s really what Mark means anyway. I think his advice is a warning for people who are hurting themselves from excessive exercise and encouragement for the sedentary by offering realistic goals

  44. Women have been know for better cardio health than men. When you think of the motion and activity performed by women, this may be a factor in better cardio health. Currently this is changing as more women work outside the home. In the past women moved all day long, due to lifting weights, (babies and children) cleaning, cooking, moving things, making beds, doing laundry, (hanging clothing on the line this was great for sun exposure) climbing stairs, walking to market or neighbors, working in the garden. This was interspersed with sitting as they did things such as shucking beans, and the intense sprints of chasing children, and then interspersed with constant weight resistance of keeping a home. Sitting around with the family listening to the radio probably lead to more movement than sitting on the couch watching television.

    I had an uncle, (shuffling Joe), who was a steeplechase runner even participating at the German Olympics in 1936. He kept running most of his life and always remained lean. He had long legs and a short torso, (our family body type). The members of my family who lived into their 90’s and even 100’s followed a Paleo type diet. Thanks for the food for thought.

  45. I get what you’re saying Mark- I’m a fan of circuit training, too. But, I noticed that you’re a former marathon runner. How can you disapprove of long bouts of cardio when you’re a marathon runner? I enjoy all forms of exercise, but nothing beats a good, long run every once and a while. Are you saying this is ultimately bad for health?

  46. Hi,

    I am training for my 2nd 50k and it has been hard to for me to keep my HR below 160 or even 165 after my first 2 miles. Do I just need to force myself to run slower or walk when it starts getting too high? I am in South FL and it is summer (85-90 degrees with 100% humidity). Its hard to run slower than 11 minute pace.