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

A Case Against Cardio (from a former mileage king)

We all know that we need to exercise to be healthy.

Unfortunately, the popular wisdom of the past 40 years – that we would all be better off doing 45 minutes to an hour a day of intense aerobic activity – has created a generation of overtrained, underfit, immune-compromised exerholics. Hate to say it, but we weren’t meant to aerobicize at the chronic and sustained high intensities that so many people choose to do these days. The results are almost always unimpressive. Ever wonder why years of “Spin” classes, endless treadmill sessions and interminable hours on the “elliptical” have done nothing much to shed those extra pounds and really tone the butt?

Don’t worry. There’s a reason why the current methods fail, and when you understand why, you’ll see that there’s an easier, more effective – and fun – way to burn fat, build or preserve lean muscle and maintain optimal health. The information is all there in the primal DNA blueprint, but in order to get the most from your exercise experience, first you need to understand the way we evolved and then build your exercise program around that blueprint.

Like most people, I used to think that rigorous aerobic activity was one of the main keys to staying healthy – and that the more mileage you could accumulate (at the highest intensity), the better. During my 20+ years as a competitive endurance athlete, I logged tens of thousands of training miles running and on the bike with the assumption that, in addition to becoming fit enough to race successfully at a national class level, I was also doing my cardiovascular system and the rest of my body a big healthy favor.

Being the type A that I am, I read Ken Cooper’s seminal 1968 book Aerobics and celebrated the idea that you got to award yourself “points” for time spent at a high heart rate. The more points, the healthier your cardiovascular system would become. Based on that notion, I should have been one of the healthiest people on the planet.

Unfortunately, I wasn’t – and that same mindset has kept millions of other health-conscious, nirvana-seeking exercisers stuck in a similar rut for almost 40 years. It’s time to get your head out of the sand and take advantage of your true DNA destiny, folks!

The first signal I had that something was wrong was when I developed debilitating osteoarthritis in my ankles…at age 28. This was soon coupled with chronic hip tendonitis and nagging recurrent upper respiratory tract infections. In retrospect, it is clear now that my carbohydrate-fueled high-intensity aerobic lifestyle was promoting a dangerous level of continuous systemic inflammation, was severely suppressing other parts of my immune system and the increased oxidative damage was generally tearing apart my precious muscle and joint tissue.

The stress of high intensity training was also leaving me soaking in my own internal cortisol (stress hormone) bath. It wasn’t so clear to me at the time exactly what was happening – in fact it was quite confusing, since I was doing so much of this so-called “healthy” aerobic exercise – but I had no choice but to give up racing, unable to train at anywhere near the intensity required to stay at an elite level.

To make ends meet…

…I became a “personal trainer” and I refocused my attention on training average “non-athletic” people to achieve reasonable levels of general fitness and health. Of course, we lifted weights as part of the overall plan (and I will go into greater detail on that important aspect of fitness in a later post), but for the aerobic component of their training, I started doing long walks or hikes or easy bike rides with them. My many clients got the benefit of me actually working out right along side them and I got the benefit of 3 to 5 hours a day of very low intensity aerobic work (well, very low for me anyway). It was refreshing and really didn’t take much effort on my part, but I knew I had to be deriving at least some small benefit from those hours.

Since I didn’t have much time left in the week for my own workouts, once or twice a week I would do a very short but very intense workout for my own benefit, usually sprints at the track or “hill repeats” of 2-3 minutes each on the bike. Lo and behold, within a year, my injuries were healing, I was rarely sick and I was even back to occasionally racing – faster than ever. Something “primal” was happening and it made total sense in the context of the DNA blueprint. I was training like my hunter-gatherer ancestors, building my aerobic capacity slowly and steadily without overstressing my adrenals or my immune system, training my body to derive more energy from fats (and not glucose), requiring far fewer carbohydrate calories from my diet, and building muscle with occasional quick bursts of speed and intensity. I was suddenly both fit AND healthy. My Primal Health system was kicking in and it all made perfect sense.

Humans, like all mammals, evolved two primary energy systems that powered the skeletal muscles of our hunter-gatherer ancestors 40,000 years ago and that would keep us all well-powered the same way today, if we weren’t so bent on circumventing them with our ill-fated (literally) lifestyle choices.

The first energy system relied heavily on the slow burning of fats to create ATP (the universal energy currency), keeping us fueled while we were at rest or sleeping, yet also allowing for continuous or intermittent low levels of aerobic activity (think of our ancestors walking across the savannah for hours foraging for roots, shoots, berries, grubs, insects and the occasional small animal). It makes sense. Fats are very efficient fuels that are stored easily in the fat cells and burn easily and cleanly when lots of oxygen is present (as when we are breathing normally). Even if there’s no food in the immediate area, a well-trained fat-burning hunter-gatherer could continue walking and foraging for days without compromising his or her health or efficiency.

The second major energy system we developed through evolution was the ATP-PC system, which allowed for intense loads of work to be done in very brief bursts (think of our hunter-gatherer ancestors sprinting to the safety of a tree to avoid being eaten by a lion). Both ATP and phosphocreatine (PC) are always sitting right there within the muscle cells, with the former providing a quick burst of energy and the latter replenishing the former as it depletes. Together, they are the highest octane fuel we have, but it doesn’t last long. In fact, it’s ATP-PC and adrenaline that allow the little old lady to lift the front end of the Ford Fairlane off her husband when the jack fails. Unfortunately, the muscles can only store about 10-20 seconds worth of this precious fuel to complete life-or-death tasks. If our ancestors survived that quick sprint to safety, however, their ATP and PC reserves were filled again within a minute or two, making available another 10-20 second slot of intensity.

Furthermore, that brief burst of intense energy sparked a small “growth spurt” in the muscle, making it even stronger for the next encounter with the next lion – a true survival adaptation.

(Note: While our energy systems are actually quite complex, varied and interrelated, I have simplified things here to make it easier to “digest”.)

Bottom line: Fats and ATP-PC were the two primary energy sources for locomotion: we either moved slowly and steadily or “fight or flight” fast, and we became stronger and healthier the more we used only those energy systems.

But here’s the real take-home message for us: We did not evolve to rely heavily on a carbodydrate-fueled energy system, and yet, carbohydrate metabolism seems to rule our lives today. Yes, carbohydrate (in the form of glucose) can play a major role in the production of energy in skeletal muscle, but it turns out that the heart and skeletal muscle prefer fatty acids (fat) as fuel over glucose.

Our hunter-gatherer ancestors didn’t regularly ramp their heart rates up for over an hour a day like so many of us do now. Even when the concept of organized hunting came along, it would appear that our hunter-gatherer ancestors relied more on superior tracking ability (using our highly evolved and exceptionally large brains) and walking (using our superior fat-burning systems), rather than on actually “chasing down” their prey. In fact, squandering valuable energy reserves (and increasing carbohydrate [glucose] metabolism by a factor of ten) by running hard for long periods of time was so counterproductive it would have likely hastened your demise (imagine chasing some game animal for a few hours and – oops – not succeeding in killing it. You’ve spent an incredible amount of energy, yet now you have no food to replace that energy. You have suddenly become some other animals prey because you are physically exhausted).

So, what does all that mean for us in the 21st century seeking to maximize our health and fitness?

Well, we know that this current popular high intensity aerobic pursuit is a dead-end. It requires huge amounts carbohydrate (sugar) to sustain, it promotes hyperinsulinemia (overproduction of insulin), increases oxidative damage (the production of free radicals) by a factor of 10 or 20 times normal, and generates high levels of the stress hormone cortisol in many people, leaving them susceptible to infection, injury, loss of bone density and depletion of lean muscle tissue – while encouraging their bodies to deposit fat. Far from that healthy pursuit we all assumed it was! What, then, is the answer?

Knowing what we know about our hunter-gatherer ancestors and the DNA blueprint, we would ideally devise an aerobics plan that would have us walking or hiking several hours a day to maximize our true fat-burning systems and then doing intermittent “life or death” sprints every few days to generate those growth spurts that create stronger, leaner muscle.

However, since allocating a few hours a day to this pursuit is impractical for most people, we can still create a plan that has a fair amount of low level aerobic movement, such as walking briskly, hiking, cycling at a moderate pace, etc a few times a week and keep it at under an hour. Then, we can add a few intense “interval” sessions, where we literally sprint (or cycle or do anything intensely) for 20, 30 or 40 seconds at a time all out, and do this once or twice a week.

If you are willing to try this new approach, but haven’t sprinted for a while, you may want to ease into it. Start with maybe three or four the first time, resting two minutes in between and, after a few weeks of doing this, work your way up to a workout that includes six or eight all-out sprints after a brief warm-up. An easy few minutes of stretching afterwards and you’ve done more in less time than you could ever accomplish in a typical “80-85% Max Heart Rate” cardio” workout. That’s exactly type of the plan I do myself and that I give all of my trainees now.

Let’s recap:

The benefits of low level aerobic work (walking, hiking, cycling, swimming):
– increases capillary network (blood vessels that supply the muscle cells with fuel and oxygen)
– increases muscle mitochondria
– increases production of fat-burning and fat-transporting enzymes
– more fun, because you can talk with a partner while doing it

The benefits of interval training (sprinting in short intense bursts)
– increases muscle fiber strength
– increases aerobic capacity (work ability)
– increases muscle mitochondria (the main energy production center in muscle)
– increases insulin sensitivity
– increases natural growth hormone production

The costs of chronic (repetitious) mid- and high-level aerobic work
– requires large amounts of dietary carbohydrates (SUGAR)
– decreases efficient fat metabolism
– increases stress hormone cortisol
– increases systemic inflammation
– increases oxidative damage (free radical production)
– boring!

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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. rb, you definitely have a good intense workout protocol. Maybe you don’t need to do it so often as you have suggested.

    Moon, if you have trained on a high carb diet, now may not be the best time (leading up to a marathon) to start fiddling with drastic carb-cutting. Get through your race and then start low-carb training fater it. That doesn’t mean you can’t fine tune carbs a bit right now – making sure you only replace the carbs you’ve burned in workouts or that you’ll need to get through tomorrow’s workout.

    Mark Sisson wrote on August 4th, 2009
  2. Thanks Mark!
    I’ll cut it back to 2x a week. I’ve also decided to reduce my distance to 75% of each cardio circuit, but maintaining the intensity. I’m entertaining the idea of reducing it to 50% (half mile run, half mile row, one mile bike) but increasing the speed.

    rb wrote on August 5th, 2009
  3. Mark-
    Great article. I have a few questions for you.

    Obviously exercise is good for you, but as with all things, too much of anything, even good things, can become bad.

    There are people out there that follow very intense workout routines, which involve working out 6+ days per week, an hour+ a day, doing anything from weight lifting sessions, to cardio. Is this, in your mind, a bit much? Is this not a great routine to follow over the long term?

    I am wondering if a better routine, which would provide good results, but also not “over-do” it, and can be followed long term, would be a few resistance training sessions per week, maybe 30 minutes each, along with a couple of High Intensity sprint workouts per week, and then add in a day where you go for a nice walk, or moderate jog. Is this more along the lines of what you say is the more ideal workout routine for someone to follow, rather than longer, intense workouts, everyday?

    The way I tend to look at it, is that exercise stresses the body. That stress, and your bodies adaptation to that stress, is what results in the changes we see. Too much stress is a bad thing for the body, which is why people can go too far with exercise, over train, and actually begin seeing negative results.


    Chris wrote on August 6th, 2009
  4. Hi, I am a triathlete and have been for seven years. I can certainly attest to chronic fatigue from the workouts. I’d like to continue on competing in the sport but I would like to do so following the primal blueprint methods. I have been on a primal transition for about three weeks now and have not trained hard since my last race in July. Does anyone know of any training plans that I can follow in order to stay in triathlon Grok style? By the way I have been doing some long low intensity runs and swims and I feel way better.

    Bob wrote on August 11th, 2009
    • I would guess Bob that to be a primal triathlete youre going to have to be less primal with your foods. All that intense exercise will will need some good source of carbohydrate energy to maintain. I’m sure Mark has answered this question thousands of times and if I remember correctly he stated you’re going to have to make some comprimises in the primal lifestle if you want to compete like that.

      David wrote on August 11th, 2009
  5. Bob, for what its worth i’m attempting to go through the same transition from long training runs and bike to short interval type training. I’ve chosen the CrossFit method which promotes only short (10 to 30 min) high intensity workouts. However I think high intensity needs to be further defined.For example 3 rounds performing a 400 meter sprint followed by 10 pull ups raises your HR close to max for the duration of the 3 rounds were as performing a push press for 1 rep 6 times with 2 minutes rest in between hardly has you breaking a sweat but both are high intensity. My point here is that I think we can handle more high intensity workouts that hit different systems. I wish i could speak more intelligently about this stuff but one thing I do know from my limited experience is that the long distance training I performed last year to compete in 3 1/2 Ironmans resulted in a weak body. My goal now is to CrossFit for the next three months and work on run and swim skills. Following the three months I will continue with the CF WODS (workout of the days) and incorporate CrossFit Endurance. I got the idea from this guy who’s performing the same program for IM Arizona this helped

    David H wrote on August 19th, 2009
  6. Mark, my coworker has been sending me your posts for awhile now and since starting a diet that is mostly in line with primal eating since April, I finally decided to subscribe to your newsletter. This article was great, but I am wondering if my workout routine fits in with this. I go to Curves and do the circuit 3 to 4 times a week. Because I have idiopathic peripheral neuropathy in my feet, I do not do very serious aerobics on the stepping squares, but do try to really do good, serious reps on the resistance machines. I also take an (for me) aerobic yoga class once a week. These exercise choices work for me, (following the adage that the best exercise program is the one you will actually do), but does this fall in line with your program or can I adapt it to your program? Thanks for the Primal Blueprint.

    Rita Potter wrote on September 4th, 2009
  7. Rita, I think you are headed in just the right direction. As your strength improves (and neuropathies subside) you can add to the load. For now keep doing what you are doing and emphasize the diet.

    Mark Sisson wrote on September 4th, 2009
  8. Uhmm fatty acids are used to make ATP. They are not two different things! Where did you get this idea and why?

    from wikipedia
    “Muscle cells also contain globules of fat, which are used for energy during aerobic exercise. The aerobic energy systems take longer to produce the ATP and reach peak efficiency, and requires many more biochemical steps, but produces significantly more ATP than anaerobic glycolysis. “

    Marnee wrote on September 15th, 2009
  9. see from above “(Note: While our energy systems are actually quite complex, varied and interrelated, I have simplified things here to make it easier to “digest”.)

    I explain ATP as the universal muscle “currency” more fully in the book.

    Mark Sisson wrote on September 15th, 2009
  10. Mark
    Would the plyo and kenpo exercises in P90X be too much?

    Ben wrote on October 7th, 2009
    • Ben, maybe just once or twice a week.

      Mark Sisson wrote on October 7th, 2009
  11. Mark,

    I found your site today. You suggest a limited amount of low-level aerobics, but am I correct that this is mostly because of time constraints? I am 51 yo, overweight, and have a lot of time on my hands right now. Would it be beneficial to do a lot of low intensity walking? And some high-intensity work like weightlifting and intervals.

    Tom wrote on October 19th, 2009
    • Tom, yes, time constraints are the only issue. Otherwise, we might be well-served by slow walking or hiking a few hours a day most days. That’s why I give a low minimum of 2 hours per week, but leave the door open for more. The rest of peak fitness/health happens by doing brief intense sprint sessions once a week, as well as functional, full-body resistance training two or three times a week. Of course, it’s all in the book :-)

      Ironic that you write today, as three “fit” runners died in the Detroit Marathon this weekend and a 13-yr-old boy died on the football field in LA, a great young athlete “who had even run the LA Marathon”.

      Mark Sisson wrote on October 19th, 2009
      • I ran a marathon once. That was 30 years and about 100 lbs ago. I exercise fairly regularly, but have not been getting satisfactory results. From what I have been reading here (and elsewhere), it seems I have been doing a few basic things wrong.

        Tom wrote on October 19th, 2009
  12. Hi Mark,

    I just found your website while doing some research on insulin resistance. I am looking to decrease my risk of diabetes, since it runs in my family and my fasting blood glucose is high-normal.

    I was just wondering if you were able to recover from the pain in your ankles. I assume since you are still exercising, the condition has become manageable. Has the diet helped reverse some of the damage?

    I am overweight and exercise has become painful. I am looking for ways to use food to my advantage and help me lose weight. My podiatrist told me I have a great deal of inflammation in my feet, which causes pain and hinders most exercise, especially “cardio.”

    I would love to hear your take on this.


    Isabel wrote on October 21st, 2009
    • Isabel, I no longer run the huge distances I used to, when I do run I run barefoot (or in FiveFingers) and fast, I stopped eating all grains (so I decreased systemic inflammation). Those three things have made me pain-free for eight years.

      Mark Sisson wrote on October 22nd, 2009
  13. Mark, interesting article, but are your opinions based on your experience only or are they supported by scientific studies or evidence, and if so I would sure love to see the cites??? Thanks

    David wrote on December 23rd, 2009
  14. Heh. I understand that it was simplified, but it’s fatty acids vs. glucose for the production of ATP, and not fatty acids vs. ATP, no? One can simplify without being wholly off-base.

    That, and I’m always baffled by people that come by and have to mention that they don’t like the mention of “evolution”. Well, sod off, then. And go read up on your bacteria and viruses. If you go all “well that’s microevolution”, do us all a favor and punch yourself in the mouth. You’re not going to miss those brain cells, anyway.

    That, and if you’re really curious about whether any of this is valid, who’s stopping you from going and seeking out the science yourself? While you can’t always get full text, PubMed is free for public use, and several medical journals allow free public access if you register. Failing that, there’s always your local college or university library.

    Rely on other people to do the research and distill it for you, and you can never know for sure whether it’s actually correct. Although judging by some of the posts on vermiculite and gardening, reading comprehension is not a common skill.

    Summary: Read a Book.
    Addendum: That’s not fiction.

    Ginger wrote on January 5th, 2010
  15. Hey there Mark,
    I came across your article today, it is quite interesting.
    I was wondering if this oversimplification is ignoring the functional energy systems of different muscle fiber types. While low intensity walking, hiking, biking is great for burning fat and increasing some endurance and promoting blood flow to oxidative fibers (slow twitch – ST) it does not strengthen oxidative-glycolytic fibers (fast twitch a – FTA). While you discussed HIT which I agree is excellent for fast twitch glycolytic fibers (FTB), the “fight-or-flight” response sympathetic nervous system fibers, it still does not promote hypertrophy or efficiency with FTAs. In the “Biophysical Foundation of Human Movement”, it is discussed that the FTA fiber recruitment bandwidth is higher intensity work lasting 30 seconds to two minutes, this seems a critical timeframe for running 400s, swimming 200s, or something primal such as rock climbing (the average boulder route is approx. 8-12 moves of high intensity and lasts 45-90 seconds).
    What is your take on the FTA versus FTB?

    Aside from that, I was curious on your take of my own regimen:
    Day 1: 1 mile of Interval Swimming in 200s, and 400s of breast and freestyle. Deadlifting, 3×8 at highest weight possible allowing complete sets.
    Day 2: 1 mile warmup, approx. 6:40 followed by approx. 2 hours of bouldering practice, climbing as hard of routes that are feasible at my level. Bench press 3×6 as heavy as possible allowing complete sets.
    Day 3: Rest and recovery including light game of tennis or swimming at a low intensity (I recall reading a few clinical studies supporting active recovery).

    I repeat this schedule every 4 days.
    This has been my winter break regimen and I will probably maintain something similar to that when I return to school.

    As for goals, I am looking to better myself overall, increasing strength to weight ratio (for climbing), strength overall, climbing intensity (I compete in bouldering competitions), decrease bodyfat % (I fluctuate between 9-10% and would like to be around 7-8%), and increase my cardio performance (VO2 Max) so I can compete in sprint triathalons relatively easily.
    I have been contemplating whether or not I have been overtraining, but I have continued to build strength, maintain body weight, improved physique, and gained difficulty in bouldering (mainly tendon based I believe – collagen deposition) and would like to hear your input on this.

    Thanks for the feedback,

    -Sorry for the novel!

    David wrote on January 8th, 2010
  16. This makes alot of sense when I sit and think about it. I cannot think of a reason that the primordial man would have to run nonstop for any long period of time.

    Wayne wrote on January 9th, 2010
  17. you provide no sources / references for some of the bold claims you make. could you be right? sure. then i’m sure there’s much evidence to support your claim. cite it

    Zé wrote on February 18th, 2010
  18. sorry for the late response but i wanted to read every post so as not to repeat.

    This does not really fly in the face of any knowledge about elite level distance running.

    I know the article is written for the common man, but I wish it had emphasized the difference a little more between elite athletes and common men. Some friends were trying to change my ideas about running after reading this article.

    I had to explain to them that elite distance runners more or less do this already.

    Examples (from my own experiences and witnessing it in countless friends/teammates)

    Mark recommends long hikes for the everyman. a sub 30:00 10k guy could run for 60 to 90 mins at the same level of intensity an everyman could hike.

    Mark recommends hard intervals divided by rest. an elite miler or 5k runner could run 8x400m’s on the track under 60 clicks and recover by running 800m’s (.5 miles) in 4:00. a common man would have to run much slower and probably walk or completely stop to achieve the same effort.

    The point is (coming from an elite distance runner), Mark is correct. If you do not have the natural talent and years of training as an olympian, you should not mimic the work load you read about that olympian doing in Runner’s World, even at slower paces. Most likely he/she will be putting forth about the same effort as you would doing Mark’s prescribed workouts.

    William wrote on February 25th, 2010
  19. Mark, I sure wish I’d read your book before I ran a marathon in 2003… it was a fantastic experience, but I gave myself adrenal fatigue and though I wasn’t overweight to start, all that training didn’t firm me up all that much and it was always so puzzling. Now it makes sense. I should have run less, lifted weights more!

    Jeanmarie wrote on March 26th, 2010
  20. I am in my late 30s. Have not done the “weights & treadmill” thing for about 5 years.

    I do about 2x “short and intense” 25-40 min. interval workouts a week. (burpees, plyo, sprints, boxing, etc) I also do Yoga and Pilates once a week, for a total of 4 days of fitness.

    I arrived at this intuitively. I do not keep track of anything. Do I have your seal of approval? My only goals are overall fitness, good physique, and healthy aging.

    PS: Going to buy the book.

    LooksYoungerThanHeIs wrote on May 7th, 2010
  21. Whenever I watch a jogger plod by I wonder, why the hell would you want to do that? It looks so painful to me!

    nathan wrote on June 1st, 2010

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