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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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’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!!!

    Jeremy wrote on June 26th, 2009
    • Well put, Jeremy!

      Mark Sisson wrote on June 26th, 2009
    • But he could move stuff all day long, when your muscles give out after an hour. What isn’t to like about that?

      Zach wrote on December 7th, 2010
  2. 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?

    Cormac wrote on July 21st, 2009
    • 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.

      Mark Sisson wrote on July 21st, 2009
      • 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.

        Cormac wrote on July 24th, 2009
  3. 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?

    Jack wrote on September 17th, 2009
    • 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 VO@ 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.

      Mark Sisson wrote on September 18th, 2009
  4. 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.

    Dima wrote on October 19th, 2009
  5. 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.

    Mark Sisson wrote on October 26th, 2009
  6. Could you provide evidence for the health issues that these people have?

    Dima wrote on November 10th, 2009
    • 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.

      Dima wrote on November 10th, 2009
  7. 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.

    Julia wrote on March 17th, 2010

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