More Chronic Cardio Talk

A few weeks back my Chronic Cardio post got a lot of response and initiated some great discussion. Since it’s one of the cornerstones of the Primal Blueprint philosophy (and an obviously popular one at that), I thought it was worth more time and tender loving attention.

And why wouldn’t anyone want to hear that real exercise doesn’t mean endless hours on that torturously boring treadmill? News like this is like sunlight bursting in, choirs of children singing, shackles collapsing open and crashing to the ground. Hordes of celebratory folk parade through the gym, penny whistles and fiddles playing, ale mugs in hand, goats and cows in the merry mix. Get off that treadmill and join us, for the love!


Truly, how many people give you great news like this on a random Tuesday– permission to leave the life of chronic cardio for the promise of less time, more muscle, better health? Of course, I’m certainly not advocating giving up all training – just that certain problematic, unnecessary type. I’d encourage you to reread all of the discussion and great comments offered up. Here’s a sampling of my contribution to that post conversation.

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

In our cardio addicted culture, it can sound too good – too simple – to be true. But the science and the research is there, folks. Short “interval” exercise, like sprints or strength training, can offer the same fitness benefits (and then some) compared with traditional endurance training. Take this study via Science Daily via McMaster University. In the context of six training sessions during a two week study period, half of the college aged subjects did 90-120 minutes per session of a continuous moderate-intensity cycling routine while the other half did between four and six 30-second intensive cycling bursts. At the end of the two week study period, the endurance cycling subjects had each invested 10.5 hours. The intensive interval subjects had invested just 2.5 hours. Yet, the improvements in fitness performance and muscle parameters were the same.

Interested in hearing more?

A studyfrom the University of New South Wales followed the fitness and body composition changes in 45 overweight women in a 15-week period. The women were divided into two groups and assigned interval or continuous cycling routines. The interval “sprint” cycling group performed twenty minutes of exercise, which repeated eight seconds of “all out” cycling and then twelve seconds of light exercise. The continuous group exercised for 40 minutes at a consistent rate. At the end of the study, the women in the interval group had lost three times the body fat as the women in the continuous exercise group. (An interesting note: the interval group’s loss in body fat came mostly from the legs and buttocks area.)

The study’s organizers, in their presentations to the Heart Foundation and American College of Sports Medicine, discussed the role of sprinting in metabolic response. Intense interval training, they said, results in higher levels of catecholamines, a compound related to fat oxidation.

More yet?

Another collaborative study organized by universities and health institutes in Denmark and Japan highlighted the same distinction in fat oxidation between prolonged, continuous exercise and shorter, intense interval routines. In addition to additional fat oxidation, the study’s results linked interval exercise with lower plasma glucose, increased epinephrine response, lower insulin concentration and increased fat oxidation during the recovery period.

Don’t you just love this stuff?? Folks, this is ground breaking stuff. Now I just scratch my head at why we keep running ourselves ragged? The message is out there, but it’s not reaching people.

We’d love to hear your experiences with interval training as well as your questions/impressions of this less prescribed (but highly effective) approach. Thanks for reading!

Abraaj, Kazze, Rosh PR, Atari, Gracinha & Marco Flickr Photos (CC)

Further Reading:

A Case Against Cardio

CrossFit: Your New Workout Routine

Interactive Health: High Intensity Interval Training

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About the Author

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

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51 thoughts on “More Chronic Cardio Talk”

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    1. Treadmills can be used for intervals, so no need to ask your gym to get rid of them.

      1. Tread mills are garbage for intervals unless your are over 80 years old. You can’t run flat out. Oap it’s good.

  1. Too bad “running” is a great big industry. Wonder how much all those marathons bring in ($$). Lots of money in selling running shoes and gear. And running magazines and books? (how many different articles do you need to read on how to run down a road?) If jogging and aerobics really worked, then obesity would of been eliminated in 1986 and we wouldn’t need all those gyms with rows of treadmills.

    People just need to realize that fat burning is an hormonally dictated event that can happen all day long…and trying to worry about “how many cal they burn” during anything is a waste of time. I mean….if we burn fat in only an aerobic state…and the only other state is anaerobic (resistance training/lactic acid)…aren’t we able to burn fat sleeping? (since that is an aerobic state) So why not set up our hormones to do so with resistance training, eating right and getting plenty of sleep to get that GH response! Intervals and other short term intense exercise are also the key to getting GH levels high!

  2. Hey Mark-

    The studies show some very eye opening results. Maybe I should start doing more interval sessions while training for my (one and only) Ironman this year – that’ll save me HOURS a week! 🙂

    However, what you noted as interesting “(An interesting note: the interval group’s loss in body fat came mostly from the legs and buttocks area.)”, isn’t so shocking. When most women gain weight, it goes straight to their rear/hips/legs, which is where they naturally store fat. I bet if the interval group was a bunch of overweight men, the fat loss would come mostly from the stomach/mid section area. This isn’t exactly ground breaking or anything new.

  3. another good study about the EPOC effect of high intensity exercise

    “These results suggest that EPOC duration following resistance exercise extends well beyond the previously reported duration of 16 h. The duration and magnitude of the EPOC observed in this study indicates the importance of future research to examine a possible role for high intensity resistance training in a weight management program for various populations.”

  4. The old paradigm will be a hard one to snuff out. I face it every day. My wife has worked at a fitness center on a Navy base for over 12 years, and she teaches 3-5 spinning classes a week–each an hour long and HARD. But that’s only after she’s done an hour on the stepmill before she unlocks the doors. Meanwhile I’m trying to help my grandson lose weight. His grandma wants him on the treadmill but Grandpa has him doing intervals on the cycling ergometer and a Concept2 rowing machine. He works hard doing those intervals but guess which type of exercise he’d rather be doing? He hates the treadmill! Gotta start ’em young! 🙂

    Dave Gets Fit

  5. Ryan,
    As a woman, I took Mark’s comment about fat loss in the thighs and buttocks as a more gentlemanly way of mentioning to the women readers that this kind of exercise is helpful for their typical problems zones. It beats, “Hey, ladies, interval training can help you trim down that big butt!” 🙂

    1. Agreed 😀 I think it’s also interesting because you can’t spot-reduce fat, yet it would appear that interval training in the study resulted in spot reduced fat in the rear and legs. Fascinating!

  6. Unless you can reference improvements and substantial values for V02 max, I do not believe your anti=cardio views will stand the test of time. V02 max values correlate directly with death rates.

  7. Great post. A few years ago, after stagnant weight loss and trying to force fat loss by running upwards of 1 hour (!!!) of moderate intensity running, I switched to much shorter weight training and anaerobic exercise, stopped counted calories, and had fat melting off of me. I’ve been like this ever since and can honestly say (despite the less time in the gym), that I eat 1.5x what I used to and can handle carbohydrates much better than I used to. A lot of us spend time in the gym, not many of us make good use of it.

  8. “Take this study from McMaster University. In the context of six training sessions during a two week study period, half of the college aged subjects did 90-120 minutes per session of a continuous moderate-intensity cycling routine while the other half did between four and six 30-second intensive cycling bursts. At the end of the two week study period, the endurance cycling subjects had each invested 10.5 hours. The intensive interval subjects had invested just 2.5 hours.”

    Are you referring to some other study? Because in the one you cite here, the control group did no training at all. That’s 2.5 hours of intervals versus zero hours to get a 9.6% improvement. From the study “The other eight subjects served as a control group that completed exercise performance tests 2 wk apart with no training intervention.” The improvements seen were only in a short-duration time trial so they may not carryover to an event that lasts 90-120 minutes.

    1. Thanks for pointing this out. This guy seems to have a problem faithfully reporting the studies he cites.

  9. “study’s results linked interval exercise with lower plasma glucose, increased epinephrine response, lower insulin concentration and increased fat oxidation during the recovery period.”

    Well sort of. They exercised at the same low intensity in both tests and for the same amount of time. But your “interval” group required 80 minutes total instead of 60 minutes to complete the protocol. It’s an interesting study but doesn’t make a good basis for training.

  10. Two things:
    1. Mark any answer to Dr. J? I am sure that training the phosphagen and glycotic systems enhance the aerobic metabolic pathway. I’ve read proof of this on Art Devany’s site. Also, my strength and stamina have increased greatly since doing the fast-twitch movement training.
    2. Dr. J, can you provide data on the correlation between V02max and death rates?

  11. Mike and Charles:
    But … treadmills are actually really good for interval workouts. A lot of them have pre-programmed interval workouts, in fact. Or, I’ll typically do a 4×1 mile on the treadmill.

    Mark, you mention sprints, but this study seems to indicate that intervals of 2-10 minutes may be more effective than intervals of <2 minutes.

    Also, it isn’t like interval workouts need to be short. Mine took 40 minutes yesterday (10 uphill and downhill hill repeats, with 30 seconds rest). Of course you can do less than that; exercise is something where you get what you put into it.

    Bryan at Evidence-Based Fitness pretty ably dissected the University of New South Wales study, which he called a “minor” but “definitely underwhelming” case for intervals. As he put it, the women in the study lost “far less than half a pound per week of fat … not exactly the dramatic transformation we all hope for after 4 months of gut-wrenching interval work.” It comes down much more to diet, I think.

    The Denmark and Japan study seems to show that two 30-minutes bouts of exercise with 20 minutes rest is better than one 60-minute bout, but a 30-minute interval is not that short or intense!

  12. so longing to know if people listen when you say this:
    fat loss depends 80% on what and how you eat.

    because they dont.
    to me anyway.

    too hard that way 🙂


  13. Dr. J,

    To my knowledge, the population-wide correlation between VO2 max and death has everything to do with general fitness vs general unfitness and very little if anything to do with differences among alreay fit populations. Since VO2max is partly weight-dependent (ml/kg) fatter people will generally have lower VO2max and will also have higher rates of diabetes, CHD, cancer, etc. So is it the lower VO2max or the poor diet and lack of ANY exercise that cause deaths? I think the VO2 comparison is a tangential marker at best.
    Can you point to a specific morbidity/mortality study so we can examine this more closely?

  14. derek,

    You are correct that it would appear that a whole range of interval possibilites opens up. Nothing special about 30 seconds (other than it’s over pretty quick :-). Could be 5 sets of 2 minutes at a slightly lower load. I got my best results as a marathoner once a week doing 5-6 x 1 mile at 4:50 with a 3 minute rest.

    The Primal Blueprint model is that our ATP-only system was geared best for all-out very intense sprints (life or death) so that whatever we can do to tap into that same stress – and recover well – would serve us best. It is always about the “experiment of one”, which is how you in your current condition can best acclimate and improve.

  15. MizFit,

    You are SO right. Diet is 80% or more of fat loss. I am now 8 weeks post-knee surgery and other than a disastrous Christmas snowboarding trip, I haven’t done any cardio or intervals for about three months (the knee was messed up for a long time before the surgery. My body fat stays constant at %8-9% purely as a result of my diet. Pictures soon to come…

  16. Beware of drawing too many conclusions about interval training. When you look at all the research to date, the steady states used for comparison have all been at a light intensity. That’s fine for fat, out of shape people but doesn’t have anything to do with people already in reasonable condition. So far, it doesn’t appear there have been any comparisons of intervals to steady state at moderate or high intensity. It is still unclear if there is any advantage whatsoever of intervals for the weekend warrior who trains hard outdoors.

  17. Dave,

    Interesting you bring that up. My own experience as an athlete and coach, and more recently through discussions with endurance athletes, suggests that the interval benefits are even greater when you have already established a base. I believe many competitve endurance athletes waste valuable time and energy doing “base work” or longer high-end aerobic work even when they have been competing at high levels already for years, when they could be generating substantially greater overall gains doing select interval work. Of course, they also need to blend in “tempo” work, which is basically “race-pace” efforts for periods of time longer than intervals, but less than long distance.

    Now for average Joe, you are correct, it would be inetresting to test higher outputs for longer periods of time…but then you’d have to train them to get to that point. I think these studies are simply designed to show that there are other – possibly better – ways for people interested in improving their metabolic conditioning than simply slogging it out on the treadmill.

  18. Hey, I like all the information Mark gave us: I thnnk he is correct. I have been working out (cardio and weights for many years). Since reading his info I have changed my way of cardio. I am now having so much more fun while working out and really look forward to doing it! My 17 year old daughter loves it too!

  19. Something I have finally noticed at age 29 is that I feel better by working out less. By giving my body a chance to heal, I am actually much better off than workout out everyday. Anerobic activities seem to provide tremendous health benefits in minimum time if the body is allowed to rest between sessions.

    In retrospect, I wish I could have reduced my running volume in high school. I essentially wore (got sick) myself out with 50+ mile weeks.

    Thanks Mark!

  20. Phillip,

    Time management is a big part of all this. You’re lucky you got the epiphany sooner rather than later. No sense crying over spilt milk (or 50 mile weeks). Enjoy your new lease on life for a long time!!

  21. “And why wouldn’t anyone want to hear that real exercise doesn’t mean endless hours on that torturously boring treadmill?”

    Here’s one reason: I’ve established a good habit of bringing a book to the exercise bike and getting some reading done while my legs take care of said endless hours of cardio. It is no strain on my patience. The book makes me the biggest poindexter around, but what else is new …

    The bike is pretty much the only kind of exercise I’ve found that allows for simultaneous reading (or am I wrong?) so I had this great formula going, and now here comes MDA and spoils it all, dagnabbit! : )

    1. Audiobooks! I listen while lifting, knitting, running, doing chores, etc. Books are awesome, and most libraries have audiobooks you can download for free, now.

  22. Gunnlaugur,

    Don’t let me spoil anything. I sometimes ride the stationary bike while reading for 35-40 minutes. I can burn 600-700 calories in that time while catching up on my reading. Of course my sweaty magazines are no longer readable for anyone else.

  23. yeah, this is a comment “bump”, but regardless – the only problem with the statement:

    “you’re free of the treadmill! Yay!”

    . . . is when I actually *like* running. The meditative state, the exertion, the miles and miles of roads or trails. It really makes you feel like you’ve done something, in a way that 90 minutes of yoga or 4 minutes of Tabata does not. I do both of the latter, as well, but still, running fills some kind of mental niche, at least for me, for now.

  24. I’m a bit new to this, and what I wish I knew is: how much cardio is too much? Is there a way you can tell, just by listening to your body? Most days, I wake up feeling like a coiled spring and really enjoy a gentle, 45-minute, five-mile run in the early morning cold. Then I might do 15 minutes of mild shovelglove.

    If I do this every morning that my body feels rested and energetic — about four times a week — will I be violating the Primal Blueprint and grinding down my health? Some days, the joy of running is so overwhelming, I can see how easy it would be to drift into running too much. Also, my job keeps me seated at a desk for eight hours a day, which makes me really crave activity when I can get it.

    I want to observe the cardio limit, whatever that may be, but I’d be sad if I had to cut my runs short or (horrors) restrict myself to walking instead.

    1. I slightly disagree with Mark’s views. Evolution has made us excellent long-distance runners, enough so that it was possible to catch prey by “just” chasing it to the point of exhaustion. That being said, I agree with Mark about rest. You will definitely know if your body has not sufficiently recovered from your previous activity. One of Mark’s articles even said to limit your exercise to about an hour. Even if you don’t want to take my advice, your exercise habits are within the constraints of the first Chronic Cardio article.

  25. The two pieces of equipment that I use is a quality heart rate monitor and my gymboss. That’s it.

  26. I have a question for Mark or anyone else who can shed light on this… I am a 45 yo female with 6 kids (yes, all mine) that has been running for about 27 yrs, about 45 minutes a day. In the last 7 mths I increased my mileage significantly to 50-60 miles per week, half of that being straight up hill (for about an hr). I was thrilled to see that I finally had a waist (I am one of those straight up and down body tyoes, skinny legs and arms) but unfortunately to get that waist of 25-26 inches, I had dropped down to 103 lbs (I am 5ft 6in) and the rest of me looked like a skeleton. So 2 months ago I started the Primal plan, lots of uphill hiking, lifting weights, sprints, and keeping my carbs to between 50-100, fat and protein high. But, after two months like this, I am seeing fat again on my belly and waist (I have a waist now of 26-27)… i am SO discouraged that I am tempted to go back to running high mileage again… anyone have any thoughts?? I am slender everywhere else, just my waist and stomach…

    1. Similar age, not quite so many kids, 26 inch waist with 130 lbs at 5’5″…look at your weight lifting regimen. Are you doing the squats and lunges to build your large muscles (glutes, hams and quads)? Are you correctly engaging your core when you lift military press or anything overhead? Visualize your belly button zooming past your spine, back and down towards your rear. Also are you getting enough rest? Might be hard to really get a true 8 hours of sleep every night with 6 kids. Lack of rest means heightened cortisol, means bigger waist. You can also try monitoring your resting heart rate every morning before getting up to see if you are overtraining.

  27. I’ve recently started with primal eating and the beginnings of a primal exercise routine (some martial arts classes for the more intense work, and making sure I take a 30 minute walk after lunch and dinner 7 days a week, and generally take stairs instead of lift etc.. ). It’s only been about 6 weeks, but I’ve lost a surprising amount of weight without feeling weak or lethargic.

    One thing I’ve noticed is that the primal ‘workout’ side of things is focussed on being strong and fast in punctuated bursts.

    I’m interested in joining up as a military reservist once my body fat is down to acceptable levels, and the main fitness test in my country is a timed 1.5 mile run, which is a bit of a longer interval (5 minutes for a serious runner, 10 minutes for a young person in ‘ok’ shape).

    What’s the best way to train for this in a ‘primal’ way? Should I just run in short bursts as for normal primal training, perhaps add a couple of 2 mile runs per week? should I go out for longer once a week?

    I’d be grateful for any guidance

    1. @new, one sprint session a week of, say, 8 x 200m with a 45 second rest between each. Then one x three mile steady run once a week (not consecutive days) should get you where you need to be if you are doing other Primal work.

  28. didnt roger bannister many decades ago begin using intervals as a way to improve running performance?? if running performance improves what specific body changes take place??? less fat and mroe muscle, improved cardiovascular operation???

    i have found that nothing improves running/cardio like running and cardio.

    good stretching to reduce injuries keeps you running longer.

    if body image is the sole issue i expect intense resistance training would be the best, and cardio/running doesnt hurt.

    if you like to run – you run. its is healthy many runners can attest to the mental benefits as well.

  29. when i run, i generally do a 6 mile run at a pace maybe at about 80 of what i could if i really pushed myself hard. the last half mile of every run i would always sigificantly speed up. that was my interval for that run. after three of those i would do a slower 8 mile run or a even slower 4 mile at a continuous 11percent grade on a treadmill workign leg strength. i made very good progress doing this. my run speed increased and they felt more natural.

  30. I’m so glad I stumbled onto this article! Whenever I venture into a season of ultra cycling I hate what it does to my body. I get fat/gain unwanted weight because I’m not doing any intervals, just endless miles of turning the pedals. Thank you for explaining this so simply and allowing for my aha moment!

  31. Hi Mark,

    Thanks so much for your website and book. Really interesting article. What is your opinion on short high tempo runs? Are they considered chronic cardio too?

    I currently do high tempo 15 to 20min runs for my cardio training, but after reading this article think perhaps I should switch to interval training!


    Olly from the UK

  32. Whenever I venture into a season of ultra cycling I hate what it does to my body. I get fat/gain….

    i have no idea what ultra cycling is…do you get less fat by masagin your ass on the couch?

  33. “Unless you can reference improvements and substantial values for V02 max, I do not believe your anti=cardio views will stand the test of time. V02 max values correlate directly with death rates.”

    me running you down in the street would also correlate with your death.

    why the non believer??

  34. I don’t really like the part about losing weight from the legs/butt instead of the abdomen. Isn’t subcutaneous gluteofemoral fat healthy on women, at least more so than abdominal visceral fat? Besides I like my curves and I’d rather keep my big butt and lose some unhealthy belly fat.

  35. This thread 2008: “Unless you can reference improvements and substantial values for V02 max, I do not believe your anti=cardio views will stand the test of time. V02 max values correlate directly with death rates.”

    Its now 2015 – looks like the anti-cardio views have in fact stood the test of time…