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!

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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178 thoughts on “A Case Against Cardio (from a Former Mileage King)”

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  1. I really enjoyed this article and I found it very informative. It is pretty long and I think it might have been easier to read with better formatting.

    My best thoughts,

    Bradley Woods

  2. Hi Mark, is there scientific evidence supporting what you’ve found in your experience? If there is could you send me a few links? I would be interested to look into this further.


  3. Men’s health magazine is suggesting that you are correct. Keep up the good work!

  4. So would running five miles in 45 minutes three times a week be considered too much?

    1. keep up the good work that is a grreat time most people i talk to don’t get that close i don’t no how old you are and what your goals are, but i’m 48 and thats what i’m doing on a hilly road surface actually around 40 min. My 4 miles in the flat surface is 25 min ian i fill a little unfit due to running in the snow i hate it can’t wait for the summer.

  5. By doing cardio 1-2 times per week and no more than 20-30 mins per section, plus total body mass training, you will minimize fat while you get bigger in muscles.

  6. Mark,

    I’m curious about what you mean by “low level” cardio. I understand that this means reducing our time in aerobic exercise, and thus going shorter distances.

    But I am still wondering about relative effort. Do you suggest that we all stay in heart zone 2? Is heart zone 3 ‘low level’? Is heart zone 4 the forbidden zone?

    Forgive me for understanding the world through the readout on my Polar monitor! Thanks for your great article,

    Mike H.

    1. Low level means not reducing the amount of time you workout but reducing the intensity level of your exercise

      1. Would 6 miles jogging 4 X per week and heavy punch bag muay Thai session be to much?

  7. Mike,

    Depends on your level of fitness. The idea is to burn only (90%) fat when you train aerobically. For very fit people, this might be as high as zone 3, but for most it will be walking briskly, hiking, biking at medium pace, etc. Then you reserve the really hard stuff for short anaerobic bursts (intervals) once or twice a week.

    Remember, all this is advice for someone wishing to maximize health, energy, longevity etc…If you are deciding to compete, then you might choose some more radical compromises.

  8. Hi Mark, Have you heard of a product called Isagenix? I have been using it and having great results. I wondered if it is as good for me as it seems to be? I’ve lost weight and have more energy, this product is a health and wellness that cleanses the toxins out of my body. All the ingredients seem to be what I need but I thought with you in the health business you would know if this kind of cleansing is good for the body? It seems to be the new thing to do, but is it the best I can do? Thanks, Roxie

  9. Roxie,

    Isagenix has a number of products. Because they are an MLM, I would not rate their products highly. OK ingredients at exhorbitant prices. Also, not a big fan of “cleansers.” That said, if you are getting the results you want, who am I to steer you away?

  10. It sounds to me like you experienced a classic case of overtraining and overuse injuries, and are now claiming high intensity cardio as the problem.

    The problem was not the intensity at which you worked, but rather the frequency by not allowing your body proper rest and recovery. All exercise is beneficial (low intensity aerobic, high intensity aerobic, very high intensity intervals) to overall health. However, you must recognize the intensity and frequency at which you work and allow your body time to recover and grow stronger.

    And exercise promoting hyperinsulinemia? That’s news to me! I’d like to see your sources on that one…

    1. I fully support Mark on this one. I was being over-trained by a Kung Fu instructor and it was only 2 days per week; but for an hour each time. I was also suffering ALL of the symptoms Mark described. I am still in recovery mode now. The cortisone was dissolving my muscles and making me weaker and I was also suffering from hyperinsulinemia. I even started collapsing. And I am a type O, which is meant to be suited to extreme exercise routines. I’m all for Mark’s method of training now.

    2. “The problem was not the intensity at which you worked, but rather the frequency by not allowing your body proper rest and recovery. ”

      You can count me as a fan of marks, but I agree with his comment 100%.

  11. Jonathan,

    Not sure you got the message here. Of course I overtrained. That’s what many many marathoners and triathletes do. That’s the point. Any exercise IS good provided you do the right amount and allow the proper rest. Most who compete do not allow proper rest.

    The necessary high carb diet is what promotes hyperinsulinemia – not the actual training. No sources necessary for that.

    1. When I first read all your posts against cardio, it was a bit much to take, as I really enjoy going for jogs and bike rides. However, in this comment you say that any exercise is good given you do the proper amount and allow adequate rest? I find I always feel a lot better and sleep more soundly when I get out and jog three or four miles/bike 6-8 miles, and don’t really need to consume vast quantities of carbohydrates. My current diet looks like fish and eggs for breakfast, usually some kind of stir fry or meat and a large tub of broccoli/green beans for lunch, and some kind of meat with a heaping plate of leafy greens for dinner, with maybe a few pieces of fruit on the side for snacks (all animal food and most plant food is organic). Assuming I could maintain this fairly primal method of eating, and my runs are conducted at a fairly comfortable pace, do you think this type of exercise is particularly harmful for my health? I do a bit of strength training as well, as not to become imbalanced.

  12. Completely agree.

    As a trainer myself I rely on diet and weight training to bring about results rather than pointless joint bashing such as running and fixed pivot shitty machines like the cross trainer.

    People used to think the earth was flat and now we know better. Its only a matter of time before people feel the same about endless hours on the CV equipment.


  13. Sorry,I wanted this comment in an another post of an another homepage. This post was in another browser:).

  14. Mark,

    I have been reading your site/blog for several weeks and am very impressing by both its content, and your positive attitude.

    In terms of fat loss, (assuming that one is eating correctly in terms of macronutrient ratios, adequate protein consumption, caloric leves), what would be your cardio/interval suggestions?

    I am assuming low level cardio (i.e. 30 min of steady state interval walking, swimming, etc) and 2 HIIT type worksouts per week?

  15. Sudip,

    2 HIITS per week for sure. The rest can be 30 minutes or even 2 hours each, as long as it’s very low level stuff (walking, hiking, etc) Once the Heart Rate gets abover 55-60% max, that’s when you can (and should) reduce the time. When you get to 75-85% max HR, you can get a lot done in as little as 20 minutes. What we DON’T want is 90 minutes or 2 hours of 75-90% Max every day.

  16. Mark,
    I think this site is excellent and have been influenced by it to try your 30 day primal challenge. Til now I have been a marathoner and steady state jogger guy.
    However I have been more persuaded by your physical condition as evidenced on your videos than by all this conjecture about how primitive humans lived.
    The fact is if you look at the San people (Bushmen)of the Kalahari who still lead stone age lives, their method of hunting is to a) dart an animal such as a kudu with a small poison arrow then b) send out one runner to chase it down and literally run it to death. The kudu sprints out of sight but the hunter keeps pressure on it by jogging steadily on its trail. It can take an entire day of steady state jogging before he reaches the exhausted animal and then he will kill it with a spear. So, based on that evidence it would seem that the ability to jog steadily for hours on end has been of great evolutionary advantage to humans. . .
    Anyway, thanks for all the great information!

  17. Joe, you must be referring to that Men’s Health article on the San Bushmen. I disagree with the premise. You’ll note that they don’t run hard and long…they “trot” which is actually the kind of low level aerobic activity I’m talking about and saying is OK. Also, they don’t do it every day (once you have a kudu, you don’t go out and get more without a nice freezer to keep the extra in). They don’t train to do this as if it’s a race against the animal. Instead they track it and methodically pace themselves while the wounded, drugged animal sprints and rests. Using their human mental superiority, they “cut the tangents” and slowly move in on the animal. All in all, if I were allowed to do that in the USA, I would consider it a totally Primal activity – one that my other intense training would allow me to do with relative ease once or twice a week. Just because we “can” do it once in a while doesn’t mean we should train for endurance events every day.

    Glad you dig the site. Keep watching.

  18. Hi Mark,

    I enjoyed your post for the most part. And I agree with 99% of what you said. The main difference is I know that I was designed not evolved. But the mechanics you describe are what we were designed to do.

    I am a molecular biologist, personal trainer and former bodybuilder so I have a deep interest in this subject.

    I found your post because I have not trained one bit since getting married 5 years ago (new baby, started my own company…etc) and just started training in Brazilian Jujitsu and the cardio intensity when “sparring” (basically wrestling) is intense!

    I find myself every two or three days (if I don’t take a day off) getting heart palpitations (with a heart rate of 48-55)… it is really anoying and a little scary. I had a cardiologist friend check me out and my ekg was ok.

    Did you ever traing anyone who went from zero cardio for over 5 years to 100% heart rate max training for over an hour? How did they feel?

    I know, I know… Do as I say, not as I do.. Hey I’m human.

    1. Maybe YOU were “designed”. If have been “designed”, I demand a full refund and a sack full of hammers. I think the kid linked in my name might want one, too. Being production line defects, and all. Your “designer” has a sick, twisted streak that results in things like ossifying tissue until the person afflicted suffocates. In my universe, it’s an unfortunate consequence of faulty reproduction processes. Which seems a lot less mentally ill, honestly.

      1. Ginger, there’s nothing wrong with somebody’s having (and stating) a different belief.

        1. What does his “belief” really have to do with this subject? Why is it necessary to mention it?

    2. Kevin,
      you can have an okay ekg and still have heart problems. I sometimes have the same symptoms and went to the doc about it. My ekg was fine. It took a heart sonogram to show where my heart was strained. More than likely from the years of overtraining I put myself through. I still train but like Mark I’ve cut way back, I listen to my body, rest whether I want to or not, and work on eating right.

  19. Kevin, normally you should spend a few weeks or months easing in to an intense training program. Gradually building up from slower aerobic activities to brief intense bursts, etc. As long as your ekg is OK, I guess I can’t add much.

  20. I know you’re right, I just don’t know how to do it with something like Jujitsu where your opponent is going full throttle. I mean if I don’t put at least equal effort, I am going to get tapped out… I’m going to see if I can get some suggestions from the instructor today.

    I appreciate your web site and specifically this page, as I have always believed the science behind what you’re saying (less evolution of course)…

        1. Twat is another word for the genitals of a woman. It can also be used to describe someone in derogatory terms. In this context I think DN was referring to Kevin’s inability to handle a little bit of BJJ. The insult was probably uttered due to Kevin’s arrogant sounding post, in which he felt the need to unnecessarily disparage evolutionary theory (why people still do this despite the extensive evidence backing it up is beyond me. Guess there must be significant signs pointing to the mainstream ulterior theories of where we come from….) and inform us of his beliefs.

    1. Know how you feel Kevin. I went into Kung Fu after children and had the exact same problems. Before then I used to be incredibly fit, did body building and the whole works. Then straight into extreme Kung Fu workouts after having so many years off and I also thought I had heart problems but my doctor also assured me that I was okay. But I had a lot of other things wrong with me instead due to the overexercising. See post above.

  21. To clarify ATP is used all the time independent of what energy system is used to generate it.

    you seem to infer ATP is not used during activity that is not sprinting.

    I also contend you are unlikely to be able to “trot” a Kudu to the point of exhaustion at a low heart rate.

    the fact the runner is not achieving a sub 3 hour marathon pace does not preclude he is making a sustained effort or that the effort is not daily does not invalidate long sustained efforts as a natural activity. The women carrying firewood on her head is most likely making a sustained effort even walking.You don’t see a lot of talking going on while women carry heavy loads for hours a day… stick 20kg on your head and walk for 4 miles

    there is millions of women who do substantially more than that 365 days a year. . however how primal is that activity?

    I think you primal model is in need of checking not least in that you have odd ideas about hominid evolution. The main problem with a primal model is there probably is and never was a standard regime.

    However interval training is highly effective but this is nothing new or absent from endurance training.

    I am unhappy with the propagation of the evolution certainties on this site.. but in your defense your training regime appears to be quite beneficial if not enjoyable, there is a large supportive social aspect

    did primal man engage in 8 high intensity sprints a day with limited recovery intervals?

  22. great read. I was a bicycle racer for about 7 years and become extremely burnt out, quitting all physical exercise for nearly two years and gaining over 60 lbs. The time investment for cycling is ridiculous, even for a mid level amateur. The accidents are dangerous and people regularly die in races. Cyclists are good at cycling, and not much else. Ask them to do pushups, they cant. One pro(JHK mtb pro) once joked he could not do 10 pushups. The average racer devotes +/- 20 hours per week. Racers now are recognizing they are developing heart conditions, due to the prolonged elevated heart rate. There is also a correlating instance of cancer among endurance athletes. I see it as a fad, and luckily I am locked in at the lower rates for my crossfit gym..

  23. No idea if you’ll get this or not seeing how old this article is, but… Im preparing for a sheriffs academy in February. They used to just run the cadets a lot. But I found out that now theyre making it worse. They are trying to get as many people to quit as possible since they dont have as many spots to fill and want people to quit.

    Now, in the current academy, they are running the cadets ~10 miles everyday, sometimes all at once, sometimes accumative throughout the day. I have a feeling it will be the same in Feb. So I have until Feb 9th to get as many miles in as possible to get my body used to the distance.

    Its only a few months, then the 6 in the academy, so Im not expecting a lot of long term health problems, but whats the best way to combat the negatives of long, slow distance? I was thinking still throw in sprint days 2 or 3 days a week. Also, keep walking and biking everyday as my main form of in-town transport.

    Also, as a former milage-king, what do you think is the best program to increase from an average of 1 mile at a time to 10 at a time?

  24. Brandon, don’t fret. Just do the work necessary to succeed in the training. You won’t do any significant damage at your young testosterone-fueled age. As long as you eat well (cut the grains and simple sugars, but you’ll need to add more starchy carbs like spuds, yams, sweet potatoes, etc)

  25. Hello Mark,
    I used to do tempo runs 2-3 miles 2-3 times a week and some strength workouts. Last summer I replaced my tempo-runs with sprints on the grass, which reduced the volume of my running. That brought down my HDL cholesterol from 57 to 44 and I didn’t like it. I thought it would badly effect the health of my arteries (I’m 71 yo). I also checked some other sources and they confirmed that cardio exercise is good for HDL cholesterol.
    I am back on my old cardio routine now with tempo-runs. It is moderate fun rather than stressful high intensity training for me. I often include intervals in my runs. I can only hope this cardio routine is harmless for my immune system, and generates not that much oxidative stress. We live and we learn …

    Thanks for your blog.

  26. Alex,

    I’m sure your routine is working well – and supporting your immune system. “Moderate fun” rather than stressful is always the key. Don’t know how much your diet had to do with changes in HDL either…it’s often a collection of different variables that causes these changes. Also, cholesterol tests are not always accurate as a snapshot. Cholesterol levels rise and fall under various conditions all day, so you may not have really even had the 7 point drop you were told about.

    I say keep doing what you’re doing, Alex.

  27. Hi Mark,

    I enjoy your site. It seems to me you are an advocate of Covert Bailey’s philosophy. Except, of course he recommends whole grain carbs. It’s hard to give up the bread and pasta! It was his book, Fit or Fat, that finally made sense to me, as to why we should exercise. Thanks for all the good info…

  28. Mark,

    Enjoy you perspective. 30 year runner, just started Crossfit and Tabata sprints. Doing 4 sets of 6 sprint of 20/10 splits. Is that too much?


  29. Dave, depends on your starting fitness levels (regardless of 30 years) and the intensity of the work. If you are doing 24 sprints at 20 secomds each, you are clearly not going all out on most of them. That’s the distance runner mentality – to do more reps at a slightly slower pace and recover quickly. What you are describing puts you in more of a high-end aerobic zone than an anaerobic burst. While your workout might prepare you for a race, if you are looking to boost HGH, increase pure sprint speed and get more bang for your buck, it’s better in this case to go all out for 8 and be “truly knackered” when done.

  30. Mitochondria development is important. Is there a certain % of HR or % of MaxVo2 that stimulates mitochondria development?

    1. Slow twitch muscle fiber 45%-75% vV02max, note though that running at this range has a “ceiling” or max. Meaning if you run at 45% you’ll reach the same max adaptation of mitochondria in a slow twitch fiber as 75%.

      1. Hi temp, yes, I am also very interested in this as I am training up for my next Kung Fu grading which has a grueling 3 hour physical included with the technical. Could you give us an article to read? Thanks.

  31. This is a very informative article, but I have a question. I run a 5k in about 27 minutes and would like to eventually get down to 20 minutes or below and be competitive in local 5k races. Is it possible to accomplish this by just doing a couple of short sprint workouts per week and doing hour-long walks or bike rides on the other days? Thanks.

  32. Hi there. I just got referred to this site today. This post is a great read. I subscribe to your theories here most definitely.

    Perhaps in line with what you say, eating more often with smaller meals, doing anaerobic instead of aerobic training along with strength training utilising compound movements which triggers a neuro endocrine response is the way to go. Now thats a long sentence 🙂 And eating Paleo.

    Nice blog. Ive subscribed to your RSS feed!

  33. Bill, you could do a few 5-6 milers a week at HR less than or equal to 75% max. Then do two sprint workouts a week: one short and super fast (8-10 x 10-20 seconds), the other 6-7 x 60-80 seconds. Fill in the rest with the hiking. That should get you closer to 20 minute 5K.

  34. Hi, love the site,
    I never post anywhere, but I think you’ve got health and fitness figured out.
    I’ve been doing this, about 3x a week:
    1 mile at 9.0mph on the treadmill,
    my ‘sprint’ for general fitness
    1600 meters in 6 mins on the rower,
    for rock climbing,
    2 miles in 6 mins on the bike,
    for mountain biking
    So it’s about 20 mins of cardio, with 4 mins recovery between each part. Then follow that with intense weight training, 3x8s. I had a 1.75x BW DL, pullups with a 35lb weight, etc. I built great for a few months, then started getting weaker and more tired. Quit for a week, and I’m about to crank it back up again. Is my cardio too much? Or should I change it from 3x to 2x a week? I’m already paleo, wheat/gluten free (recovering celiac), sardines, tuna, lots of other animals, raw, whole veggies, fruit.

    I’ve got BCAAs on the way, for pre-workout. I’ve fasted twice before to quit smoking, but I’m going to add one fast day per week now.
    I’m doing a lot of things right, just wondering if the cardio is excessive, and if I should ease up a bit, or go from 3x to 2x a week.

  35. Hi Mark,

    What if I am training for a marathon and I need to maintain an increasing amount of mileage until the final race?

    I just started the primal diet about a week ago and I would love to continue to see and feel the difference for myself. But I am wondering if that is wise since you said that one needs high levels of carbs to sustain a intense cardio like this. Must i stop running if I enjoy it just because I am going on a primal diet?

  36. 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.

  37. 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.

  38. 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.


  39. 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.

    1. 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.

  40. 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 https://www.gotrimax.com//TriMaxEvan.htm..hope this helped

  41. 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.

  42. 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.

  43. 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. “

  44. 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.

  45. 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.

    1. 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”.

      1. 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.

  46. 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.


    1. 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.

  47. 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

  48. 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.

  49. 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!

  50. 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.

  51. 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

  52. 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.

  53. 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!

  54. 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.

  55. Whenever I watch a jogger plod by I wonder, why the hell would you want to do that? It looks so painful to me!

  56. I have one severe doubt with what you’re saying, Mark.

    You say that our primitive ancestors weren’t designed for long running chases, that instead we were foragers who walked a lot.

    That just doesn’t seem to be the consensus among the ideas coming out of evolutionary biologists nowadays.

    As a species, we suck at sprinting (We’re far slower than quadrupeds), we’re not very strong, and in a chase we’re far less agile than quadrupeds. So why haven’t we died out? We must have some evolutionary advantage, and it’s not our brains – our ancestors were physically nearly identical to us long before they developed our immense brain capacity. We didn’t even invent projectile weapons until less than a hundred thousand years ago.

    It turns out we are fantastic long distance runners. Some of the best in the animal kingdom. If you put a horse against a man over 50 miles, the man can win! Now, horses are also fantastic long distance runners. Most other mammals wouldn’t stand a chance.

    The gist of how this helps us hunt (and thereby gain the vast amounts of protein and fat to create and maintain our disproportionately large brain) goes back to the heat of Africa. We’re hairless, we shed heat well, and we can run a long way pretty efficiently (because as a biped we don’t have to shift gaits to move faster like quadrupeds do, so we can suck in more air when we move faster than they can). This means that in the heat of the day we can simply run a Kudu to death, as it collapses from heat exhaustion and dies.

    Seriously. No kidding. There’s a video on Youtube of some bushmen doing it. Just search persistance hunting.

    What’s even better is that the smarter we got, the better we got at this kind of hunting (higher brain function makes us pretty amazing trackers, despite our less than proficient senses).

    A lot of what I’m talking about can be found in Christopher McDougall’s book “Born to Run”. It’s a great read.

    So I guess I’m wondering how to jive your idea with this idea about long distance cardio.

    Ultramarathons are becoming more popular, with very fit (and not ridiculously, dangerously, thin ) people running for days at a time.

    1. “You say that our primitive ancestors weren’t designed for long running chases, that instead we were foragers who walked a lot.”

      @George, I don’t know where you get this. I never said we weren’t designed to run…I just said we weren’t designed to run long and daily the way so many people do today. The fact that you are fit enough (and biomechanically able) to run a 10K doesn’t mean you have to run one every day. I guarantee you that even though persistence hunters can jog/track/chase prey for a few hours, they don’t “overdo” it on successive days.

      1. It was mostly in response to your explanation of our energy systems and how they relate to our ancient predecessors –

        Ala “The first energy system relied heavily on the slow burning of fats, 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.”


        “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).”

        It seems though, that while the initial phase of the hunt was walking and tracking, the chasing of the prey over miles and miles was the actual mechanic of the kill. Our feet were our original weapons.

        I do understand what you’re saying about the daily grind of long distance aerobic activity, however if you look at the extremes of human endurance – ultramarathoners – they garner far fewer injuries than common runners while averaging impressive weekly distances. There is a debate about self selectivity, but there’s an even larger debate about the advent of poor running technique from improper footwear.

        I think, however, I’ve found the connection between your philosophy and the other ideas that have been percolating around in my brain – intensity.

        While there are certainly athletes who can run six minute miles end on end on end, maybe what the average person needs is to run at the pace where they can achieve enough oxygen uptake to continue to metabolize fat. That would put it in the same category as your 3-5 hours of low intensity activity.

      2. Hi Mark,

        I’m not sure if you like links to other sites being posted on here, but all this talk of persistence hunting and hunters, I thought it may be worth people actually watching an example:


        Title is “Absolutely Fricking Amazing “Persistence” Hunt!”

        Couple of great points in this video:

        1) highlights your case about tracking and walking for hours

        2) shows that it is only ONE hunter that does the “chase” (likely a matter of preservation for the tribe… best “jogger/runner” does the chase, but not all the tribe exposes themselves to the chance of death). Also I noted in this video he wasn’t running flat out all the time, he jogged, walked, ran, stopped, drank, assessed, and continued.

        3) REALLY highlights the reverence and connection our ancestors had to their environment and hence their food!!!

        4) Sir David Attenborough states right at the end, whilst they had tubers and roots collected, it is the MUCH more nutritious, energy giving meat!!!

        I think a lot of the persistence hunter folk have read an article, but not actually watched what it is all about. And none of what I just watched is at odds with what you have stated:

        1) We jogged/trotted/walked over vast distances
        2) We did not do this routinely, as it was risk to chase prey (note the “sacrifice” of one of the tribe, for the actual chase in case it didn’t work out)
        3) We valued meat and the bigger animals, and we respected our food sources

        This last point really hits home.. I wonder ow many people rip into a steak, with no regard of where it came from, how it got there and the animal that gave its life for us to eat. When you see the respect and care that the bushman takes when killing that animal, the vegetarian arguments of cruelty are not as valid.

        Awesome work as always!



        1. Hi Mark,

          Also found an article about this type of hunting, which is written by Louis Liebenberg.

          He has a table of data that shows the distance travelled, as well as the average speed during the hunts (also shows if they were successful or not – most often not from his sample).

          Anyway, average speed is shown as between 4.2 – 6.6 km/h although it would seem the successful hunts were at a speed around 6km/hr (one hunt was 10 km/hr).

          For the non-metric of us that is 2.61 miles/hr – 4.1 miles/hr (with the 10km/hr hunt equating to 6.2 miles/hr)… Hardly what most runners would call a a “race pace”…

          In fact, I’d call that walking!!! Or most likely, walking/jogging/running/resting/walking etc etc

          Anyway – thought this may help clarify for those that seem to believe persistence hunting is contradictory to what you are saying about humans not being “Born to Run”



          1. Thanks Mark,

            Glad to be able to contribute!

            I have a link – which is the one I found when I quoted the figures – which is just on some guys website. It gives a PDF copy the published paper.


            Because it looked like published paper, I did a search and found the published version in Current Anthropology. Volume 47, Issue 6, Page 1017–1026, Dec 2006, but you need to pay to see the published article.

            I have also found some further info, from a paper published in The Journal of Human Evolution, in which the authors conclude:

            “a persistence hunt, even at optimal running speed, would have been extremely energetically costly, considerably more so than a persistence hunt at optimal walking speed.”

            By optimal running speed, they demonstrated that there are running speeds in which running is more efficient than running at other speeds, HOWEVER whether running at an optimal speed or non-optimal speed, in terms of energy efficiency, ALL running speeds are less energy efficient than walking.

            From the same paper [my own edits/comments in square brackets – all other brackets are the authors]:

            “We calculated the cost for an individual… to travel the 27.8 km of a typical persistence hunt (Liebenberg, 2006), while walking at near-optimal speed based on the equation in Steudel- Numbers and Tilkens (2004). This cost would be 1407 kcal, 57% of DEE [Daily Energy Expenditure] (compared to the 72% of DEE to travel the same distance at optimal running speed). Walking is thus considerably cheaper. Whether optimal walking speeds could be used in a persistence hunt is, of course, another question. Given that tracking is often required (Liebenberg, 2006) and that the average pace reported for the persistence hunts observed by Liebenberg (2006) was a speed at which humans can either walk briskly or run slowly [the speeds I referred to previous post], it seems likely some mixture of walking and running speeds would be used, mitigating the cost of a hunt carried out solely at running speeds. Unfortunately, for all of our male subjects and most of our female subjects, their slowest running speed was the least efficient (see Fig. 1). Thus, selecting a slow steady running pace for a persistence hunt would not be a good energetic choice.”

            I don’t know about you Mark, but that seems like the author is saying that the persistence hunters walked and tracked, and then did short sprints/runs to keep the animal moving, followed by more walking/tracking as walking with intermittent running is more energy efficient than slow running at a steady pace!!!

            Again – to me – this fits in exactly with what you are saying!

            Link to that paper is:


            Hope that contributed a tiny bit more to everything you have gathered and provided for us all.

            My years in sales and marketing in the pharmaceutical industry researching and reading papers to back up claims has finally paid off contributing something concrete and worthwhile to the understanding of human health! 🙂



          2. Thanks, Luke. Most of this is in agreement with my theory that, while we were born to run biomechanically, we certainly weren’t born to run long, fast AND daily. The fact that normal all-around Primal fitness allows you to do a trail run or jump into a 10K race once in a while and enjoy it doesn’t mean you are better off doing that every day – or even three days a week. It’s clear to me that persistence hunters aren’t keeping a steady HR of 80% max for hours, but are walking, running, stopping, etc., moving fractally the whole time. Then they take a few days or a week where they don’t run. I’m all for that.

  57. I can see both the points of Mark and George. I think any type of exercise, be it weight lifting, sprinting, long distance running, etc., etc., can cause harm if there is not enough rest given so the body can recover. Overtraining is a real issue with people. It causes injury and negative side effects regardless of the form of exercise. Long distance running is not unhealthy, in fact, is actually very healthy. Running a marathon everyday, however, and not giving your body proper rest and recovery, is not good. The same can be said if you go out and sprint everyday or don’t give the muscles enough time to recover from a weight lifting session.

    1. I have a LiveJournal friend who runs marathons just for fun (by the way, she’s also overweight–I love trotting her out for people who think fat folks are incapable of athletic pursuits). But it doesn’t look all that fun to me. She loses toenails a lot. There were probably circumstances under which primal people had good reasons to run long distances–sometimes they hunted that way. But not everyone did that and, of course, no one hunted every single day. Maybe a couple, three times a week at most.

      I don’t know if I’d call long-distance running “healthy.” Maybe “not unhealthy enough to kill you.” If you like doing it, do it. As you quite astutely stated, just don’t overtrain.

  58. Luke,
    Great stuff. I read “The Old Way” about the San Bushmen people with great interst and had concerns about how their practice of “hunting by running,” fit in with Mark’s excercise concepts. A recent Scientific American article about how well adapted we are to running long distances in the heat reinforced my concern. However, the 6-10 K per hour pace for these hunts reported in the research you found, along with the fantastic condition of paleo human hunters makes it pretty clear that most of the time these hunts were taking place within the fat burning aerobic range of the individuals.

    Also, watching the Tour de France right now and checking on the heart meter readings, its also clear that those super atheletes are keeping their heart rates < 70% of max most of the time. (And they are still totally wiped out by the end of the month.)

    Mark, Thanks for your work on Diet and Fitness. I look forward to reaping the rewards of your program.


  59. Hello Mark,
    Thank you for confirming my suspicions! I bought the whole HIIT all the time myth and did at least three HIIT sessions (about an hour each) for years without results. Instead, I got sicker, more tired, had aching joints and hardly lost weight!

    After learning to listen to my body, I changed the way I ate and exercised, and it’s quite funny that the diet that I ate is almost like the Paleo diet, and my new aerobics workout is like the one you recommended!

    Now I do lots of walking (about 30 to 2 hours a day at time), swimming and stationery bike cycling, all low intensity. I do HIIT sessions too, and exactly like you recommend – at 20 to 40sec bursts!

    It goes to show that if you listen to your body it will tell you what it needs and wants 🙂

  60. Hi Mark,

    I am obese and a type 2 diabetic. I lead a walking group on Meetup.com for those of us who are under-athletic. I started this group to save my own life and hopefully help others in the process.

    We walk twice a week for at least 2 hours logging 4 to 5.5 miles each time at a speed that fluctuates around 3mph. There is a short hill on the trail that we call “cute butt hill” where we change it up and take longer strides and sometimes a faster pace. I have been doing this since March of this year.

    I am also a new member of an outrigger canoe club. I row once a week for about 45 mins to an hour. I have been rowing now for 3 weeks on Sunday and it affects my entire body. Every muscle hurts until Thursday!

    I try to eat right most of the time, avoiding “white carbs” and bad fats. And I have still not lost one single pound! This scares me. What am I doing wrong?

  61. > Thank you for confirming my suspicions! I bought the whole HIIT all the time myth and did at least three HIIT sessions (about an hour each) for years without results.

    I think you’re confusing HIIT with “aerobics” You can’t do HIIT for more than 20-25 mins. And Mark is promoting HIIT, not against it. I think you meant “long slow cardio” was bad for you.

    1. Yes, that’s right. I meant long aerobic sessions, though I did do high intensity sessions for 40 minutes too. I was crazy.

  62. Excellent fitness (e-book) however
    no one ever said that competition level fitness was healthy or a model for general wellness! Your (current) approach is great though.

    The 220-age formula should be dumped however. It is going to give a way-too-low level of exertion. It is better to use an RPE method if the actual MHR isn’t known.

  63. Maybe If There was no spin class,only hills to climb on a bike,You would see those nice butts.I am sorry.But your way off on that one.Cardio,Done right,Is the best:O

    1. What gives a cyclist a nice butt isn’t the cardio, it’s the leg work. Your butt is basically the tops of your thighs mushed together. What makes your legs pretty usually makes it pretty too.

  64. That is EERIE. I just read a link from Facebook about a guy who lost 100 pounds cutting calories and running. I’ve put the link into the “website” box here so it’s not spam-filtered. Look at him. Is this what you guys call “skinny fat”? Sure looks like it to me. I’m happy for his weight loss but he could look *so* much better.

    And right after reading that, someone on my friends list shared this post of yours. Are you psychic or something? 😛

  65. What are the affects of doing hot yoga. I do it about 4 times a week in a heated room. I do find it increases my blood sugar levels, I am type 1 diabetic, no one can seem to figure out why. Does hot yoga increase cortisol levels. I have noticed my free radicals have increased by the increased amount of oxigenation.

  66. I do hot yoga 5 x week. What is this classified as and is this too much.

  67. Good site: The theories expounded here are generally accepted now.

    The short “intense workout” programme (as opposed to long runs!) to enhance weight loss, increase HGH production and aid all round well being is further discussed here:

  68. Mark –
    I’ve up until this point run high school XC. I’m chronically injured (tendonitis, et cetera), stressed, and frankly often overworked during the season due to homework, extracurricular activities, honors academics and 35-50mi/week of relatively intense training. Is it worth running the sport, sticking it out until I graduate (I’m varsity), or do you think it’s probably doing me more harm than good?

  69. Hi Mark,
    I so enjoyed reading your article. I am a Middle School teacher, youth sports trainer and exercise enthusiast. I train my soccer players in the off-season and pre-seasons for “function” and subscribe to your “Primal” philosophy. However, I need to take more of my own advice. I have almost the exact same symptoms as you did when you were 28, most likely b/c I am undernourished and overtrained. How long did it take for your body to feel back to “normal” again? What did you do initially to stay active after you stopped running in order to make the transition into a healthier body. I am not sure if I should just stop all activity until the aches and muscle soreness completely stop. Can I continue to weight train and just back off the cardio to 20-30 minutes. Thanks for your advice.

  70. I’m training for my third marathon and teach lots of group fitness classes at a gym at the same time. I also work a desk job, so all my time spent not working out is pretty much spent parked at a computer. I recently have been experiencing some serious fatigue so I went to the doctor and had blood drawn to find that my glucose was unusually low. I then did a 4-hour fasting glucose tolerance test to find that my body overproduces insulin. I had NO idea why or how that could happen until I stumbled across this article today. So I’m thinking I need to change my workout routine and start cutting back on the carbs… I’m starting to see a little clearer finally. I’ve always been really opposed to cutting back on carbs because I know that my body needs them because I put it through such long hard workouts… what an ephiphany!!! Less cardio. Less carbs. Less fatigue.

  71. I do HIIT for my cardio conditioning, and maybe 30 minutes of moderate intensity running to train my muscles, but any longer than that and I’m just making it harder to recover from my workouts… at least from my experiences. I have to agree with this article.

  72. My tipping point was when the prescription for seborrheic dermatitis stopped working altogether. For years I was filling presciptions for either a topical cream or oral sterroids. Both prescriptions slowly became less and less effective until to point they became useless. Every dermatologist I went, I have seen many over the years, always claimed the same thing. No change in diet will help. They were all wrong. Once I switched to Primal all signs of seborrheic dermatitis are gone. Curing this condition means so much to me, it is not all about vanity. Walking around with flakey skin all over my face (had it really bad) most of the time was affected all of my day to day interactions with other people. Most people will avoid “David the Lizard King”, and that is lizard king in a bad way not the Jim Morrison way.

  73. Excellent! Just read this article and the Primal Blueprint book. With regards to running, it makes perfect sense, common sense even! Take, for example, the marathon run which is 40+km in honor of the guy who, according to the popular story, ran that distance without stopping in order to deliver a message… and then DIED ON THE SPOT. Isn’t it the moral of the story in this case to avoid such strains on one’s life if possible cause it can kill you and NOT to be inspired to emulate the guy?

  74. Mark: I agree whole-heartedly. I have been a massage therapist for 14 years and I have come to the exact conclusion. I find people causing themselves more problems by overdoing it then under doing it. The exercise machines should be thrown in the ocean. They WRECK people’s bodies. Everybody should get off them. Walking is the best exercise and then I tell my clients to do whatever sport they want for fun, because they will then not be prone to injury the way the machines set them up to be. Walking stabilizes, calms, eases the body into homeostasis. Everybody should walk 3 times per week and that is really the minimum needed for overall body health. Breath, Walk and Stretch. After those are in place then Pilates or core strengthening. I am not big on upper body strengthening, because it usually causes more pressure and tightness which turns into pain.

  75. Hi Mark.

    I am a 64-year-old yoga teacher, and am fairly fit.

    One of the places I teach at three days a week is at a University, and I take the metro to get there. It is 1-1/2 miles from my house to the station (I can walk a 15-minute mile).

    I was thinking of walking to the metro and back again, and two of the three days a week, on the way home, (about half way home,) I would change to jogging and doing 6 sprints along the way.

    Is that too much, or does it sound right to you?


  76. Back in the day, when I started mountain biking, my strategy was: sprint up the mountain to catch, keep up with, and pass the experienced mountain bikers… go hard ’till I blew up. It was intuitive interval training.

    Then all my MTB buddies said “Nooo your doing it wrong.. just ‘sit & spin.’ You gotta learn to suffer.’

    Ok, so I did. But lo and behold, I got slower. Only when I went back to interval training, mixed in some plyometrics, did I launch back into some speed. And I feel better and have more fun. It’s fun to “shoot in spurts.” haha. Cheers, recovered chronic-cardio’ers!

  77. Dear Mark…I am new to your site. A friend led me to your newsletter and free cookbook downloads…and now I’m here. Yea! I’ve been reading all the comments and notice most are from young athletes. Well, I am not young and not an athlete, although very active…Still working as a hairstylist and feeling pretty ok. I’m a 70 yr old lady who still feels young and always thinking young. I’m 5’4 and weighed in today at 148.5….I have a vision of getting rid of this never ending mid-section. I have been doing Leslie Sansone walk/jog dvd’s and def feel better after… I like the idea of your blueprint and getting back to true nature with eating habits. I’ve been doing something like this for a while and trying hard to stay clear of whole grains, going gluten free…blaming it for skin breakouts I’ve had for the past 2 years. Not sure it’s working though. Do you have any recommendations for a senior in getting fit, loosing weight and building strength especially in my core and legs. Thank you for all you are doing to help us get fit and healthy.

  78. I’m a 29 year old female, and I find that a 2-4 mile run and stretching a few times a week offers me a huge stress relief, not to mention that sweating is a great form of natural detox. Personally, I find a tempo run a lot less abrasive on my body than weights and sprints.

  79. Burn calories from either carbs or fat. It does not matter as long as you burn enough in absolute value. It takes longer to burn equivalent fat calories than carbs calories from high intensity exercise. Being fit and athletic requires a balanced exercise routine. Weight lifting alone is not natural while running is. If you can’t handle the heat get out of the kitchen.

  80. I’m not arguing that you’re wrong, but I have to say… I feel so great after a hard cardio workout, and fear I wouldnt get the same satisfaction from the low level cardio taking over. That said, I used to do primarily interval workouts in college, with weight training, and was at my healthiest weight and overall condition then, so like I said, not arguing that you’re wrong about the superiority of this primal plan in terms of health benefits.

  81. No doubt you are right. But it ain’t that big a deal either, everyone that is not type A (like you and I), knows this. My dad told me 35 years ago (holy crap!!) what you are saying when he would see me exagerating everything. But I could not help myself. As a matter of fact, I have done my most intense stuff as I turned 50. It also took being this old before my intensity-seeking personality got the better of me. I have backed off some, but I wonder if when you go with your gut everything still works out. The injuries I developed were definitely intellectually driven (I had never run before and took on running marathons); I DECIDED, i wanted to achieve this and I did, but I never enjoyed it. At least not the exercise itself, sure, I enjoyed the achievement. Instead I have played soccer very intensely for the last 40, never missing more than 2-3 weeks. It is super-intense and 2 hours but never more than twice and usually just once a week. Weird, but I stayed in shape with that, can feel recovery takes a couple of days but I enjoy the shit out of it and don’t really have to make myself do it. Maybe that is the real guidance, not coming up with a method but repeating the things that feel “right”.

  82. Mark,

    I realize this is an old article, but I’m going to ask my question anyway. Like many Americans, I have a desk job. Throughout the day, I look for ways to walk more. I park at the end of the lot, take the stairs, walk to a coworkers desk instead of emailing, etc. But it only adds up to so much. I perform resistance training 3 times a week and do HIIT twice a week. That adds up to less than 4 hours of intense exercise per week. Given that I spend such a huge portion of my day sitting, I’m wondering whether I can add more exercise to my routine. In the past, I performed 30-60 minutes of moderate intensity cardio before breakfast. Not only did I shed quite a lot of fat, I also felt great afterwards and never saw signs of overtraining. Do you think it would be wise to reintroduce this type of cardio, perhaps for 30 minutes every morning, I actually enjoy it and feel like it would make up for sitting around all day. It would be moderate intensity, nothing extreme.

  83. I agree that low intensity is the best for fat loss and maintaining muscle mass, but if you like to do something with high intensity, then why not? I think that primal lifestyle is all about learning from our ancestors. They certainly didn’t pay attention to low intensity/high intensity exercises.

  84. Found this article really informative and enjoyable to read it was really interesting, i learnt alot 🙂

  85. One of my biggest qualms with this inculpation of chronic cardio is the incorrectness in defining low aerobic work. Hunter gatherers were much fitter than we are now. Their low aerobic work would be equivalent to a 7 min/mile run, based upon research of the most efficient running pace (for a male, in this case). I understand not wanting to nudge people in the wrong direction, but there should at least be some room for improving our aerobic fitness. I’m sure most people, if trained at a purely aerobic running (e.g. nasal breathing throughout the whole run), would be able to improve their aerobic strength significantly. WIthout too significant a stress placed on the body.

  86. Great post, I totally agree! Here’s why: 5 Reasons To Ditch Steady State Cardio

    Slower metabolic rate – Traditional cardio tends to break down lean muscle tissue, it’s this loss of lean muscle that results in a slower metabolic rate.
    High cortisol release – This causes a breakdown of muscle tissue (slower metabolism) and increases fat storage or deposit fat, specifically around the abdominal region.
    Lowered testosterone and HGH levels – Low T-levels are associated with lowered libido, depression, anxiety, increased body fat and decreased muscle tissue. This contributes to muscle-wasting and lowers the basal metabolic rate. This means men get fatter by performing steady state cardio because they lose muscle and lower the hormones that allow them to burn fat.
    Poor time efficiency – Interval Training is superior to steady state cardio for calorie burning and fat loss. From a time efficiency stand point, you can burn more calories in less time using interval style training.
    Extra potential joint stress – Running injuries are common as the impact, stress and repetitive movement pattern often affects the hips, knees, ankles, and feet of distance runners.

  87. This is an interesting article. Thanks. I could relate to a lot of it.
    I personally feel much better now than a year ago when I was training for a marathon. Walking, barefoot running short distances, subtle changes in diet and lifestyle and more strength training have been much better for my health and well-being.
    It is also interesting to note that inflammation is now being linked to depression, as well as the diseases you mentioned in the article. Perhaps excessive endurance training and misinformation is also contributing to an increase in this disease in society? What are your thoughts?

  88. In many ancestral traditions, there is a saying : “what ever you do do it moderatly”. So the article is probably wright

  89. The immunocompromised part especially I wouldn’t be surprised if in a few years that was the next research “bombshell.”

    The establishment touts exercise as a way to boost your immune system, but as a teen the biggest hinderance to keeping up a regular exercise program for me was that after a couple weeks of consistent cardio I’d end up with a cold. I’d push through but feel like crap, so I’d be forced to stop to recover…then be off the wagon, and a couple months later when I mustered up the motivation to exercise regularly again, the whole cycle would start over.

  90. Hi Mark,

    I have been getting into a primal diet, with ups and downs, since November now. Prior that I had been a vegetarian for over 20 years! Abut 3 years ago I started running and totally fallen in love with it. Lost nearly a stone and started getting into swimming and cycling. At my peak performance I weighed 58 kg ( the lightest I ever been) but still had that stubborn belly fat.
    There were health reasons for which I had to change my diet, but I also had discovered a cross fit and needed to increase protein intake as I was too weak to perform. That was when I started to pay more attention to what I eat and started paleo diet ( I have cheat days thou!).
    At the moment I weigh over 64kg and still have this stubborn belly fat(!), Now, I am aware of muscles being denser than fat, so I assume that’s the reason for my weight going up ( but is it thou?!). However, I don’t feel or look any leaner than before. My waist is still the same, my back got actually bigger (swimmers shoulders) and let me put it that way; I can’t squeeze in many of my dresses any more.
    Now, it is mind boggling, as I do not know what to do to burn that stubborn fat but still be able to perform in my races ( half marathons, swimming )?
    I am probably over training (5-7 day/week) but I do have rest periods and my trainings aren’t all at the same intensity ( on average:1 long run+1 track session, 2-3 easy runs,1 long swim+1 high intensity swim and 2 crossfit sessions ).

    I feel a little bit demotivated at the moment, and with all the mixed messages re cardio pretty lost!

    Any thoughts on the subject would be much appreciated.
    Tank you.


  91. I am aware that this is a past article, but there have been recent (Aug/13) scientific studies that confirm this https://www.sciencedaily.com/releases/2012/11/121129143456.htm. I enquired into this topic because i have been intrigued by it. As a 40 year old woman who’s exercise is regime, for the most part has been weight-based since the age of 18, I am in great shape. My body also bounced back quite quickly after having 2 children. Long cardio sessions have never really interested me, I found it boring, I would push myself to do cardio simply because i thought i was doing the right thing. During the times i did do long cardio sessions i found it stressed my body, I experienced fatigue and i also consumed more. This article makes complete sense. In fitness follow the golden rule ‘listen to your body’. Love your work Mark!

  92. Ever heard of a guy called Ryan Hall? Haile Gbrselassie? No?
    Well just google them up. I wouldn’t consider these guys “underfit”

    But well, of course, us serious runners and other sports people do interval training too… just that with less than in 45 minutes we are just at the start of our warm up.

    What about a nice 10 miler with 8x 1mile intervals ?
    Or a Yasso800 anybody?


    Bah, boring…. XD

  93. I know that running can cause harm to your feet, knees, ankles and feet. Especially running on concrete. My heart is excellent too, and I do not exercise. The great pitcher Sachel Page said he never ran. Always took a slow walk to the mound. Our bodies were not created to endure stresses from outrageous exercise. You will pay for it in the end.

  94. Just want to share my routine in case it helps anyone. I’m also looking for constructive criticism.

    30 minutes HIIT cycling- 12 mph for 6 minutes, 18 mph for 3 minutes, repeat

    45 minutes of Ashtanga Yoga (some call it power yoga but I do traditional Ashtanga)- alternating standing and sitting series

    Rarely, 45 minutes of pilates instead of yoga- traditional mat Pilates, mostly ab and leg work

    Previously I was doing the same HIIT cycling routine but one hour per day and very infrequent yoga. I reduced the cycling to avoid chronic cardio.

    Based on this article and some conversations with friends about chronic cardio, I’m thinking of changing my routine to:
    15 min low intensity cycling and 45 min yoga 5 days per week
    30 minutes HIIT cycling with 30 minutes pilates 2 days per week
    1 day off every 7-10 days

    Feedback welcome! Thanks

  95. Mark, I fully agree with the use of interval training as part of one’s workout. I started training in August, once every 3 days doing a 1/8 mile run (almost an all out sprint) and had the following results: HDL increased from 40 to 53 (has never in my life been taken and shown over 40), 1.5 mile run time increased by 1:30 in 7 weeks’ time from 14:12 to 12:42 and not only did my 1/8 mile time increase from 1:09 when first starting to a low of 40:81 (avg for 6 sprints was most recently 43.8), but I have been unable to get my heart rate above 164 (I’m 46 years old). When I started it was normally around 180 with a high of 194 one day – you can really feel it at that rate!

    Have not been eating primal but intend to do so as part of my new year’s resolutions and cannot wait to see what the results are.

  96. It is beyond me how someone can sustain 80-85% max heart beat anyway.. for me, everything else (either muscles or breathing) will give up long before I can reach even a 140 pulse.. and never in my life have i even tried to work out for more than an hour continuously…

    1. I am not in excellent shape, I’d say I’m average to a bit above but I can easily get my pulse up to 170-180. I don’t try to sustain it, I run 1/8 mile intervals, basically sprints, then walk the other 1/8, then sprint again, etc. 6 times, takes abt 25 mins total but only abt 5:30 of it running. Works great, got my hdl up from 40 to 53 from that alone and improved my 1.5 mile run time to 12:42.

      Have not been doing it for abt 2 months, hurt my achilles, but going to try and do a bit of it tomorrow even if it’s a 1/8 mile jog….my ankle will decide to fast it is going to let me run.

  97. Bonjour Mr Sisson,

    Je veux vous remercier de votre témoignage, l’expérience donc vous nous fait par, je l’ai aussi vécu , en partie. Il est tellement difficile de ce laissé aller et ce donner le temps de ce reposer dans la société actuelle. Vouloir gagné, être le meilleur , passe souvent par un chemin qui nous rend étranger à nos besoin. Je me suis entrainé, moi aussi, au point où je me suis blessé.

    Mon orgueil m’aveuglais , oh! ubris, péché si doux. Les blaissures étaient profondes. Après cela, par hasard et par la force des choses, j’ai changé ma diète et mon entraînement.

    Je faisais 4x65km de vélo par semaine , plus de la course sur 10 et 15 km 2x par semaine . Après un été à sentir une douleur de plus en plus aiguë s’installé dans le bas de mon dos, j’ai consulter un médecin. J’ai me suis fait une entorse et la douleur était de taille, 1 mois immobile , je me sentais dépérir.

    Après ma convalescence forcée par la douleur et la peur de celle ci, j’ai opté pour une nouvelle routine de vie moins exigeant, je marchais pour aller au travail 5 km l’aller et 5 km retour chaque jour, deplus mon travail consiste à marcher beaucoup ( patrouilleur à pieds). Et vue que je ne pouvais plus enduré le stress de longue séance d’exercice, je me suis mit à passer au parc à côté de chez moi, juste quelques minutes par jour , (+- 10 minutes, push up , chin up , petit séries de 30 secondes, 20 secondes de repos le plus que je pouvais faire). Parallèlement à cela, ma diète à beaucoup changé, lorsque je m’ entraînerais au vélo et à la course, je mangeais des pates midi et soir. Et maintenant mon alimentation tourne autour des fruits et du poisson.

    Le changement fût majeur, meilleur cardio, augmentation de la force et de la masses musculaire, j’étais sidéré. Les années de sur entraînement m’avait apportées bien des malheurs, mais en quelques mois d’entraînement facile et court, une progression inégalée. C’est comme cela que j’ai trouvé votre témoignage, je voulais comprendre pourquoi.

  98. I can walk for several hours, lift heavy things (myself) but I cannot sprint without being half-dead the next day for several days, the muscle pain is terrible. It just doesn’t feel right to me. So I think for an average person, there must be another approach towards getting fitter. There must be something inbetween walking and all-out sprints. I don’t think this is the right approach for me. Thinking long about it I have tried running at a speed that is slightly too fast for keeping the pace for very long, but is faster than if I’d say I wanted to start jogging. As long as it feels smooth and easy, I run. As soon as I get uncomfortable I walk until I feel ready again. I have done this for about 5 k every third day and within very short time I started to feel much better and the muscle pain is not bad at all and doesn’t leave me destroyed. I think Mark’s approach is something for already fit people who are used to some sort of running. I think sprinting is very demanding and doing all-out sprints is something for very fit people already. It is not a way to become fit when you are just used to walking a lot.

  99. I’ve never thought about this approach. I will start to integrate some short intense work like sprints, sounds fun!

  100. Hey Mark,

    I am doing body building and getting quiet big – now I want to get a bit more skinny on some parts and besides cardio what can I do? One month without cardio and I am looking like a fat person because of high ammount of water that my body gets in.

  101. Hi Mark, this is a very helpful article. This is a topic that I have researched in the past, and I always see contradicting arguments on behalf of fitness experts and enthusiasts. But, now my understanding of this topic is much clear. However, I am still confused in regards to what activities are considered good cardio or bad cardio. What about skipping rope or HIIT?

  102. I’m slightly confused by the summary which states that the types of exercise “Increase Muscle Mitochondria.” Did you mean to say that it increases the productivity of the mitochondria in your muscle tissue, or that you are actually increasing the number of mitochondria in the system. The statement seems to imply the latter, however I believe that since mitochondria are part of the whole genetic blueprint that makes up the cell, you cannot simply add more mitochondria. Eventually there becomes a space issue in the cell. On the other hand, are you simply stating that the overall number of muscle cells increase, thereby increasing the number of your mitochondria? That explanation seems to make more sense, but it was not clearly written that way.

    1. Yes, you can increase the number and efficiency of mitochondria in muscle cells through a process called mitochondrial biogenesis. Certain signals from training (and from your diet) upregulate the genes to accomplish this.

  103. The information here is very good. This post alone is still running from 2007! I had been doing perhaps too much cardio lately, for example, 1800 steps on stair master at 150-165 HR for 46 year old, and not enough resistance training. Now working out more “downstairs” at Golds w trainer and seeing results. Also using Garmin a Vivofit to make sure I take 10,000 steps per day, which seems consistent with avoiding chronic cardio.

    On April 28, 2014, I started Paleo type diet that has now morphed into a paleo-gluten free version. I used to think Gluten free was annoying and trendy, but the key is to know what you are consuming (dietary or knowledge) and see what works for you. The results of paleo GF for me have been easy to achieve and have also been somewhat astounding, including better sleep, no indigestion at all, lost 20 pounds eating meat, eggs, and colored veggies with nuts for snacks. I can feel results of carbs if and when I eat them in larger quantities.

    Looking to focus on Tabata / HIIT now, and enjoy added benefit of shorter workouts from dropping chronic cardio habits.

    As Mark notes in Primal Blueprint, Motivation or the Big “M” is key and having “Experiments” and goals will keep you going. I recommend the Primal Blueprint to all these posters.

    We tested yesterday and I now have 6 new ambitious targets for 8-15-14 testing. Will let you all know how the intensity and Slow-and-Easy training works.

    Thanks for this resource to help us become educated and get motivated.

  104. Hello there Mark! I liked this article. Just found it online and I felt the same way back then as well. It does show a society too obsessed with cardio till they are overtrained and burnt out. Which ultimately leads to more eating. Which is another topic in and of itself. In the midst of all that aerobic work whatever happened to the anaerobic side? A balance of the two is preferable but most tend to eschew sprinting altogether. Or worse, they intersperse it with slow jogs. In essence it becomes fast-jog-slow-jog. Which is more endurance based.

    In the Air Force I faced this dilemma a lot. It’s part of the reason the military’s obesity rate is increasing despite the toughened fitness standards. Too much time is spent on overemphasizing distance runs but almost zero time is spent doing any speed work (that ISN’T fast-jog-slow-jog based). Without any type of sprinting, which will actually increase one’s power, getting faster is almost out of the question. Usually our well-meaning PTL’s would spend so much time doing so much endurance based workouts our older members wound up injured. Our PTL’s weren’t sprinter types so much as Prefontaine types. They had great stride lengths which led to high PT test scores since the majority of the score was based on the 1.5 run time. As for the older members the sessions could be grueling. It was to the point where once retired so many of them swore to never exercise again! Don’t get me wrong, sprinting without proper warming up could also send them to the clinic for a profile as well, but there is a right way and wrong way to start off speed work which can minimize the likelihood of that happening.

    I did make it to retirement (and no, I most certainly do not feel that way) but I have to agree that too much emphasis on one and not the other leads to overuse injuries, among other things. I decided to focus my gym time on strictly bodyweight calisthenics and improve explosiveness with my own bodyweight over time. Initially it was difficult but as it got easier over the course of a month. I then decided to add a 45 lb. backpack to my shoulders and continue with that. I limit the reps to 5 per set as I am not looking to become supersized, just super strong in a compact body.

    The results are amazing, to say the least. I have been prepping myself to get back into sprinting and this training seems to lead the way to it. Developing explosiveness with the strength gains but not oversized with bulk. The joints are becoming more solid yet still flexible. When I retired I was 215. I weighed myself about a month ago and was at 189. That’s in the ballpark of ideal weight for sprinting with max power and not too much weight. I haven’t bothered measuring my waistline because I am retired now and am not interested in that. I’m sure its around 30-32 tho. Just with this plan alone I’ve wound up going right back into active duty shape.

    Final part (which is no surprise to anyone on here, i’m sure): diet. I’d like to say I dieted the right way initially but sadly that was not the case. When stressed I don’t eat. I go into hyperactive mode. By the time I started going to the gym I was just under 200. But since I have been doing calisthenics with my backpack I’ve had to eat more to maintain the new muscle. A good part of my diet has been bananas. That gives me energy, keeps the potassium-sodium levels on par, and helps with amino acid utilization. Doing this daily gives me plenty of energy throughout the day. I have been going to bed much later and sleeping like a baby thru the night. About 7 hours later I am up and out the door again.

    Every two to three days I go to the gym but I don’t spend more than 45 minutes tops there. The workout sessions are brief but powerful. Lot’s of explosive movements with my backpack. That’s more than enough to deplete my glycogen stores when I am finished. Since I am trying to keep the fast twitch muscle fibers in a ready state I limit cardio to a three mile walk around the city every 5 days or so. Many times I’ve been asked am I attending the local college here and whether or not I am playing half back on their football team. I laugh and thank them for the compliment…but tell them I am a retired military vet…then I reveal my true age : (

    But it’s all good. It just confirms what the article said. And look on the bright side. With more recruitment of the fast twitch muscle fibers and depletion of glycogen stores the body requires more rest and more carbs to repair, replenish and strengthen them. Your margin of error on your dieting increases a bit more. You can take 2-3 days off and come back tech refreshed, stronger and most certainly quicker!

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  106. Great article with some good info. I’ve believed for a long time that fat free (which means sugar full) is not the best fuel for our body. Thanks for the info.

  107. Found this article really interesting and shed a new light in exercise methods in recent years. In my opinion these days exercise routines are bit inhumane. To shed a few founds we have to exercise so much more. Thank you for this interesting article. Cheers.

  108. I’m assuming that high intensity aerobic exercise means doing the tempo zone or higher all the way. Am I right? Power or heart rate zones would be helpful. I find that I need a HR monitor to avoid pushing too hard.

    There’s a chart showing exercise duration vs all cause mortality reduction. 90 minutes of total exercise reduced it by about 35%, 50 minutes of vigorous exercise reduced it by about 45%, and 100 minutes of moderate exercise reduced it by 30%.

    The target HR for moderate exercise is 50 to 70%. The target HR for vigorous exercise it 70 to 85%.

  109. You mentioned Ken Cooper’s aerobic points system, which I have used for 10 years now (I’m a 67 year old male who gets most of his points from swimming laps with some resistance exercise). Dr Cooper’a recent research that a person my age should get 45% of his points from circuit training so he is more in agreement with you than you think.

  110. What about 6 miles running 4 times per week and then heavy bag muay Thai 4 times a week, pads, and sprints 2x per week fitted in?