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

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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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. 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.

    Migraineur wrote on February 4th, 2008
    • It’s pointless and stupid unless you want to stay the same as you are.

      Gelgamark wrote on November 16th, 2012
    • 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?

      Jordan wrote on February 13th, 2013
    • 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.

      camdwy wrote on April 1st, 2013
      • 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.

        kfg wrote on June 22nd, 2013
      • 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!

        kfg wrote on June 22nd, 2013
  2. P.S. I think my laptop weighs as much as an antelope. Maybe a small one.

    Migraineur wrote on February 4th, 2008
  3. Migraineur,

    That’s all perfect stuff. Real Grok-like. How much to mop my floor twice a week (no cats)?

    Mark Sisson wrote on February 4th, 2008
  4. 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 ,)

    Vasco wrote on February 4th, 2008
    • Can you post the article? Thanks!

      Derek wrote on October 14th, 2012
    • Which car will last longer?

      Jeremy wrote on June 4th, 2013
  5. 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]

    sammie wrote on February 4th, 2008
  6. 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.

    Vasco wrote on February 4th, 2008
  7. 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!!! :-)

    Dave C. wrote on February 5th, 2008
  8. 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”


    tatsujin wrote on February 5th, 2008
  9. 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!! :-)

    Dave C. wrote on February 5th, 2008
  10. 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.

    Vasco wrote on February 5th, 2008
  11. 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!) :-)

    Dave C. wrote on February 5th, 2008
  12. 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??

    Mike OD wrote on February 5th, 2008
    • Now all you need to do is provide scientific evidence for this.

      Zach wrote on December 7th, 2010
  13. >>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.” :-)

    Dave C. wrote on February 5th, 2008
  14. 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!

    charlotte wrote on February 5th, 2008
  15. 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.

    Mark Sisson wrote on February 5th, 2008
  16. DaveC,

    Good to hear that. Those crossfit guys have some very cool stuff! I incorporate it too.

    tatsujin wrote on February 5th, 2008
  17. 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.

    Mark Sisson wrote on February 5th, 2008
  18. Glad you like it!

    Chris wrote on February 5th, 2008
  19. Mark – who mops twice a week who doesn’t have pets? Besides, wouldn’t that drive me over my intensity limit?

    Migraineur wrote on February 5th, 2008
  20. 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!

    DaveC wrote on February 5th, 2008
  21. 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.

    Chris wrote on February 5th, 2008
  22. 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.

    DaveC wrote on February 5th, 2008
  23. How about Tabata intervals? I looked up several studies, and they all seem supportive (one study indicates that they are superior to intervals with longer rests). See

    Stuart Buck wrote on February 5th, 2008
  24. 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.

    Mike OD wrote on February 6th, 2008
  25. 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! :-)

    Dave C. wrote on February 6th, 2008
  26. OH…and one more thing…fitness magazines aren’t even close to dispensing worthless advice when compared to golf mags!!! :-)

    Dave C. wrote on February 6th, 2008
  27. >>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.

    derek wrote on February 7th, 2008
  28. 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.

    Mark Sisson wrote on February 7th, 2008
  29. 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…

    derek rose wrote on February 11th, 2008
  30. 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)

    Mark Sisson wrote on February 11th, 2008
  31. 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?

    Amelia wrote on February 19th, 2008
  32. 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.

    Mark Sisson wrote on February 23rd, 2008

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