Kurt G. Harris MD

PāNu means paleonutrition. The "paleo" here signifies "old" and not necessarily paleolithic. The PāNu approach to nutrition is grounded on clinical medicine and basic sciences disciplined by knowledge of evolutionary biology and paleoanthropology. The best evidence from multiple disciplines supports eating a pastoral (animal-based) diet rather than a grain-based agricultural one, while avoiding what I call the neolithic agents of disease - wheat, excess fructose and excess linoleic acid.

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Exercise in the PaNu scheme

Ketowarrior, in the comments section of the last post, correctly guesses that I have more thoughts on physical training and exercise than what I blog about. Here is my response to his attempt to draw me out. No references, just general thoughts.

I am not shy about endorsing what I like or criticizing what I don't. You have been reading the blog long enough to know I try not to make pronouncements about anything without a lot of thought first. In medicine we often say that we know about 50% of what we do is useless, we just are not sure which 50%! That's how I feel about my state of knowledge and level of certainty on workouts and fitness. I am not really a fitness blogger, but I'll give you some of my gestalt on physical training that goes against the "normal science" of physical conditioning and health.

1) Eliminating any one of the Neolithic Agents will do you more good than any training regime at all, even if you are completely sedentary.

2) As Jason and I have suggested and Barry Groves also says, 80% of health and longevity is diet.

3) As alluded to by the "cardio causes heart disease" post, extensive endurance athletics is not only not going to make you healthier, it is at best neutral and maybe even harmful to overall health.

4) Despite #3, minimal amounts of repetitive endurance activity may have positive health benefits via effects on mood and cognition.

5) Fitness is not Health. Fitness is a functional definition of physical performance. Some aspects of fitness contribute to health and maybe longevity, others do not.

6) I like Dr. Doug McGuff's book. I think strength training more than twice a week is unnecessary or even counterproductive. I agree with his debunking of the idea that there is such a thing as "cardio" training - that you need to specifically train your cardiovascular system, as if your heart and lungs get no training with your pulse at 180 doing Olympic snatches!

7) Walking is an excellent evolutionary activity that we are, simply, evolved to do and doing it is nothing but good. I agree with Sisson on this - lots of low intensity rythmic activity can be good.

7) HIT in general has some elements of a fad right now. (Don't attack, I do it myself!) I am sure it has many benefits and is superior to chronic cardio, but for non-athletes the pendulum may have swing more than it needs to away from Jim Fixx.

I'll comment on Crossfit specifically in the next post.

Reader Comments (22)

Excellent thoughts, Dr. Harris. I'm looking forward to reading your insights into Crossfit.

December 26, 2009 | Unregistered CommenterMike

In total agreeance with the above.

There is enough fitness stuff out there. Keep doing what you're doing :) Don't attack, I do #3.


When I say something doesn't save your life, I am not saying don't do it ;)

December 26, 2009 | Unregistered CommenterGrok

I put the Smily after the wrong sentence. I have a love/hate with "cardio"

I hate that it takes longer to do
I hate that it's not really good for you
I hate that it's my favorite method of exercise

I love doing it when I have time to allot to it
"may have positive health benefits via effects on mood and cognition."

December 26, 2009 | Unregistered CommenterGrok

Wow this and the last post are definitely what I was looking for before the end of the year. I started following Panu and the Body By Science method back in september, but fell apart at the end of November due to Thanksgiving and then a birthday happening every week till Christmas. I had lost 15 pounds In september and october, and wasn't totally strict about following Panu, my goal was to just stop some bad eating habits before the new year...in the past 5 weeks I put back on 10 pounds due to all the celebrations and the weather keeping me indoors much more, but I'm not going to beat myself up over that, it has just shown how much better and easier it is to just not eat certain things. Plus my energy levels have dropped compared to how they were in October after 6 weeks of eating Panu.

Anyway, going to take new measurements tomorrow and get back on track, no point in waiting for the new year to start a new lifestyle for good.

And thank you for this great blog! I'm going to send these 2 posts to my brother who is in the Marines Special Operations Batallion, he is the one who set me on the path towards a meat-rich diet a year ago, which led me to here. Happy holidays!

December 26, 2009 | Unregistered CommenterPotter

Dr. Harris:

I posted this question on Dr. MCGuff's site but it was probably the wrong forum as it is diet related. Needless to say, nobody addressed it. So, I will give it here-the exact post from the BBS site. Any comments would be appreciated or even direction to a previous post:

What are the best outcome measures to determine a healthy diet? Body composition? blood sugar regulation? Blood markers? Feelings? Functional ability? Any comments would be appreciated.


It is mostly a negative definition in my book. Having as little cancer, diabetes, degenerative diseases and autoimmune disorders (diseases of civilization) as possible is my definition of health. If you want to add being happy and physically fit in a functional sense, I would not argue but to me those are different ends that overlap partially with but are not subsets of physical health.

December 26, 2009 | Unregistered CommenterThomas

Dr. Harris,

Thank you for the thoughtful response. Your overall sense of how exercise relates to health mirrors my own. Too often in the health and fitness communities these distinct concepts are conflated. Many people are shocked to find out that a body with a fitness model like physique could harbor heart disease or cancer while a softer sedentary less fit appearing person could be disease free.

Still you skillfully parry my attempts to nail down the specifics of your exercise regimen. :)

I'm grateful for the informative gestalt overview, nonetheless. It is, as I suspect you realize, more instructive than the specifics anyway and dovetails nicely with the rest of your parametric approach.

I look forward to the CrossFit post.

Best regards,

December 27, 2009 | Unregistered CommenterKetoWarrior

Kurt, Thanks for your insights and rationale. I know it's not your thing, but if you had to ruminate on body sculpting what would you prescribe? More / Less Protein, More / Less Weights, More / Less Carbs peri-workout? WP

KGH: I have no idea.

December 27, 2009 | Unregistered CommenterWinalot


Good to see you blogging again! I think I speak for all of us readers here, noting your conspicuous absence as of late, and looking forward to reading your stuff!

December 27, 2009 | Unregistered CommenterPatrik

" I have more thoughts on physical training and exercise than what I blog about."

Kurt, basic question, but would you mind differentiating between "physical training" and "exercise", or do you view those terms as equals?


Hi Anthony

I am using them interchangeably, but I also of think of physical training as a subset of exercise.

Exercise is anything physical that "exercises" the organism. For paleolithic man, that would be daily life. Physical training is purposeful exercise to try to achieve some effect, whether improved sports performance, ability to shoot your longbow without difficulty, enhanced mood or improved health or longevity. I don't utterly dismiss the last two, but they have definitely been oversold since the 1970s "running makes you healthy" mythology.

December 27, 2009 | Unregistered CommenterAnthony

I haven't read the book, but Mcguff's views on machine vs barbell/dumbell in the interview seem strange to me. Yes, machines can be safer, but I think it's because people do too much with free weight or do free weight exercises with bad form. You can go into a gym and watch men do bench press as fast as they can, so of course their shoulder or pec is going to get injured. Also, at the gyms I've belonged to I think most of those who can box squat 315 could max leg press 1000 without training for it. The % of those who could max squat 315 without training for it would be less. Certain exercises promote overall strength much better others. For me pull ups, bench, squats, and deadlifts seem to work best. If I go up on deadlift, my bench will usually increase a little too.


I prefer free weights to machines as well. Training the muscles that you use to balance the weight makes you more functional.

December 28, 2009 | Unregistered Commenterzach

I used to do a routine of squats, bent rows, barbell presses and incline presses and did very well with this routine. Lately, however, I have been doing a lot more machine work and am really enjoying it. Yes, there is less "stabilization" required using machines (ie. leg press vs. squat) but I feel a much greater targeted effect when using machines in a high intensity fashion. If you are doing slow reps (like what Dr. McGuff prescribes), the compound exercises using machines are far superior than free weights in my opinion. I also feel much safer doing heavy weights with machines. So, I have started doing my heavier, failure training with machines and doing lighter, higher rep work with free weights (often dumbells) to also get that stabilization effect that comes with free weight compound exercises. As the higher intensity, heavier machine work takes very little volume and, I think, it doesn't require a high volume of free weight work to get that stabilizing effect, these workouts have become very efficient (and are very hard). I rarely to more than 30 minutes of work per workout and do well on two (sometimes three) workouts in a week. This is higher than what Dr. McGuff recommends but is far less than what I used to do (I also find myself moving more and more toward his recommendations as time goes on).

December 28, 2009 | Unregistered CommenterThomas

The best book I've read on what is known about strength training and exercise and the body's response to it is "Practical Programming for Strength Training" by Rippetoe and Kilgore.

December 29, 2009 | Unregistered CommenterTony

Great post - as always

December 29, 2009 | Unregistered CommenterChris

By the way, I interviewed Doug McGuff if anyone is interested:


KGH: Thanks, Chris - I remember that interview - that was where I first heard of him.

December 29, 2009 | Unregistered CommenterChris

Dr. Harris,

Firstly, I'd like to thank you for all the great information you provide here on your blog. I stumbled across your site via Mark Sisson's, whose site I stumbled across while searching the web for information on low carb diets and sprint sport athletic performance. In the 4 months since I've found your blog, I have fully subscribed to a PaNu style regemin, save for the 12th step. I've also thoroughly enjoyed reading GCBC, N&DD, and Catching Fire. Aside from nutrition, I'm very interested in exercise prescription & sport performance--I hold a BS in Kinesiology and a MS in Exercise Physiology. After reading your recent posts on exercise, I'd like to offer the following points ( I've read Doug McGuff's book in the past 2 days)-

Areas where I agree with Dr. McGuff's book are his reccomendations regarding frequency and volume. However, I can't agree with his advice to use machines as well as the rep speed he reccomends. I'd be very skeptical of anyone claiming that superslow training is optimal for expression and stimulus of fast twitch muscle fiber---if you are purposely slowing down the speed at which you execute a rep, then you are not taxing fast twitch muscle fiber optimally. Furthermore, if you are using a weight that you can control for upward of 20 seconds on a single repetition, then you are using a weight that is not capable stimulating high threshold motor units, thus under-stimulating your fast twitch muscle fiber. I was left scratching my head by the claim that the goal is to stimulate fast twitch muscle (which I agree with), yet the way to do this is by utilizing superslow rep speed (which I highly disagree with)---these, as far as I know, work in complete opposition.

KGH: Good points although McGuff might argue that the terms fast or slow mean something different.
My main concern is that very few folks are able to do workouts to true failure - it is harder than people think. Machines are good for old people from a compliance and safety standpoint but there is no substitute for the functional strength you get with compound exercises with free weights.

As for Crossfit-

I think they have some good fundamental ideas regarding overall fitness and metabolic conditioning through high intensity, short duration exercise. However, the area where I disagree is in the use of high repetition olympic lifting, and excessive reps on single exercises in general (ie hundreds of pull ups in single sessions). Don't get me wrong, I enjoy the circuit style, highly intense design, however, the actual rep/exercise prescription in many cases is not good IMO. Another blog I have stumbled upon that advocates a modified Crossfit-style program is the Theory to Practice blog. The author, IMO, has done a great job of taking that which is good about Crossfit, and tweaking the bad to create a more auto-regulated, fast-twitch focused metabolic workout containing similar benefits and less risks.

Just my 2 cents.

Love the blog!

KGH: TTP - that is Keith Norris, right? I'll have to read more of that soon.
The thing that bugs me about Crossfit is the dumb proprietary jargon (Fran, Metcon..) and the "puking is good" mentality - but those are minor quibbles. It makes more sense than marathoning for sure. I'll take them to task for nutritional idiocy soon enough.

December 30, 2009 | Unregistered CommenterBrian

@ Brian:

I hold a Kinesiology degree as well and work as a clinical exercise instructor. I have been following Dr. McGuff and his writings for some time now as well as HIT style literature starting back with the writings of Arthur Jones in the 60’s.

I think a big misunderstanding with this style of training, and particularly muscle fiber recruitment is that you do not need to move fast in order to recruit fast twitch muscle fibers. Your last 2-3 repetitions of any given set should be brutally hard and therefore your attempt to lift the weight fast (despite your inability) engages and fatigues the fast twitch muscle fibers.

The greatest benefits to adopting a slower rep cadence are:

1. Safety – F=ma …therefore the faster, more accelerative movements put greater stress on your joints, ligaments and tendons increasing your risk for injury, short term and long term.
2. Efficiency of work. Slower movements involve less momentum (which is an external force) and therefore forces your muscles to work harder through the entire ROM.


“Machines are good for old people from a compliance and safety standpoint but there is no substitute for the functional strength you get with compound exercises with free weights.”

You could lift a bag of rocks over your head and if the stimulus was great enough it would elicit a training effect. Your muscles don’t know the difference between a dumbbell and a machine.

You also use the term “functional strength”. That gets thrown around way too often IMO. What does that mean? Are you saying that the large thigh muscles and the accompanying strength I’ve developed over the past 4 years using a leg press, leg extension and leg curl machines are not functional? They function just fine thank you ;)

That being said I also believe that the barbell dead-lift is one of the most excellent and intense muscle building exercises in the world.

Love your blog Kurt.

KGH: I am glad you like the blog.

My personal experience and I am obviously not alone in feeling this way - is that free weights can be used with fewer compound movements than a roughly equivalent regime with multiple highly constrained machines to give me the functional strength that allows me to lift heavy objects like the wheels for my sportscar, shoot a longbow, haul a deer out of the woods, chop wood, climb a tree. Free weights are harder and more dangerous (I acknowledge) to use. If so, how can the results be equivalent? Is there no neural training at cortical and cerebellar levels when ancillary groups of muscles are required to balance the weight?

I think it is a tradeoff - free weights work better but are harder to use properly and not as "safe"

I can definitely handle heavy unconstrained weights that don't run on grooves or in tracks better in my daily life by training with similarly unconstrained weights in the gym. Just like sprinting seems to help when I sprint. That is my definition of functional strength - sorry if you think I should not use that word ;)

December 31, 2009 | Unregistered CommenterMatt M.


I think you are confusing strength with skill.

KGH: I can usually tell when I am confused. Perhaps you mean conflating. OK, if you want to start defining the ability to lift things as "skill" then the definition of strength has been dumbed down to "the ability to use the weightlifting machine".

All of the activities you listed require some practice/skill to become efficient at the movements, thus making it seem easier to perform them.

KGH:Beyond the initial learning, no they don't. I can shoot my longbow pretty accurately without touching it for over a year.

That is where the neural training takes place, according to basic motor learning laws. As, I’m sure you know, specificity is key with your practice.

KGH:You cannot train specifically for every conceivable novel thing - that is absurd.

I would disagree with you that free weights are “harder” if you mean in terms of muscle stimulation and fatigue.

KGH: I don't mean that - I mean harder in the normal english sense of the word - difficult.

“Hard” is relative to the exercise, the weight you select, the ROM you work through and the order of the exercises you perform. Free weights feel “harder” to use because they require greater neural attention to coordinate the movements, which is why I believe for general strength training, are inferior to a well designed machine.

KGH: That is exactly what makes them superior, IMO.

You can lift much heavier loads and, theoretically, induce much greater fatigue to the target musculature if you are not worried about the weight crashing on your head, or, more likely, straining a joint. Machines also require much less attention to control allowing you to put that attention towards maximal effort.

KGH: I get that part of the "theory" - don't necessarily agree that is an advantage.

That being said most machines you find in conventional gyms are shit. I have the luxury of being able to workout with MedX machines at our clinic which, in my opinion, are amazing and I have experimented with a lot of equipment over the past 14 years (I am not endorsed by them or getting paid to say this). Given the choice at a conventional gym that has shit machines I would definitely workout with free weights.

KGH: So now we need a "special" type of machine as most of them are "shit" - You just made my case against machines far better than I could have myself.

Anyone who tells you the secret to health is a special proprietary diet, vitamin, supplement or machine or even a training program is likely to be selling something. Not saying you are selling something, but that has been my experience.

I am not as articulate as Dr. McGuff, but he has written a lot of great things about skill conditioning and skill learning.

KGH: I like his book - don't agree with all of it in the implementation. I shall continue to prefer free weights despite arguments to the contrary and would in fact prefer not lifting at all to the machines I have encountered.

Let's get back to nutrition, this physical training back-and-forth is boring. The practical relevance of all this stuff from fitness coaches and other "experts" to health and longevity for most people is an order of magnitude less important than diet. That is why I don't usually blog about it unless asked.

And I am sorry but I would never pay a trainer a single dime to tell me how to lift weights or run on trails. Most of the bodybuilding/training workout world is just selling pseudoscientific complexity, just like most of the nutritional world is about selling dietary complexity and supplements.

Thanks for your thoughts.

December 31, 2009 | Unregistered CommenterMatt M.

@ Matt

Disclaimer-Despite my criticism in my previous post, I liked Dr. McGuff's book. I think there was a lot of good information presented and I enjoyed reading it. I think we agree on the end training goal, but we differ significantly on how best to achieve it. I think the BBS method is far superior to any marathon-esque training, and the information Dr. McGuff has provided can only help to educate people to move to a highly intense, less-frequent workout regime. A few points (in no particular order) -

-I did not say that SS/BBS can not stimulate FT muscle fibers---I said I don't believe it can do so optimally. Why do you feel it is necessary to first fatigue slow twitch fiber to get to fast twitch fiber? Seems like an unnecessary step to me. Plus, Im not interested in stimulating slow twitch fiber, which, as far as I know, has been shown to negatively effect fast twitch fiber expression.

-I fully understand that speed of movement isn't necessarily crucial ie. using maximal rates will stimulate HTU's irrespective of concentric lift speed. However, I do believe that purposely slowing down a movement is counterproductive.

-The idea that machines produce equivalent stabilization forces compared to free weights is, IMO, incorrect. Read some of Mike Clark's research from NASM. Lots more required by the body when you are not exhibiting force on a fixed plane of motion.

-I don't know how much I buy the idea that free weights are more dangerous than machines. Perhaps in the acute sense when lifting free weights with bad form, but otherwise I don't think the claim is strongly supported. Furthermore, I believe that strictly using machines for resistance training is far less optimal for injury prevention when transferring gains to real life tasks whether it be carrying groceries, shoveling snow, or playing basketball.

-Where is the momentum in a deadlift or olympic lift?

-I am weary of anything claimed to be optimal that either requires me to purchase a great deal of equipment, or must be done in a specifically equipped gym requiring membership or perhaps a certified instructor.

-I believe that just as PaNu attempts to mimic the evolutionary metabolic millieu, our fitness should mimic infrequent, anaerobic, fast twitch, power expression work that IMO is optimal for expression of the human genome (stolen from Mr. Norris @ TTP). Can BBS accomplish this optimally? I don't think so. Is it better than the majority of what people do? Absolutely.

@ Dr. Harris

Couldn't agree more with the annoying, macho BS from Crossfit. If you don't puke you aren't working hard! Gotta love the "Uncle Rhabdo" t-shirts as well. Ugh. That being said, I couldn't agree more that it is far superior to 'jogging.'

I also think that Mark Sisson's exercise pyramid is a great guide to get people on the right track. Lots of walking/hiking type activity, 1-3 intense resistance sessions/week lasting no more that 25-30 mins, intermittent 'play,' and a nice sprint session every 7-10 days if fully recovered.

KGH: Agree with all your comments - I very much like Sisson's barbell approach - low intensity (like walking) ad lib and infrequent HIT and lifting. Skip the chronic cardio in the middle.

I loathe the idea that I can't be fit with only access to the outdoors and few hundred dollars of equipment. I only belong to the local "Y" so I can avoid running on ice in the winter!

December 31, 2009 | Unregistered CommenterBrian

Hearing about HIT on a paleo site is great. When HIT is adressed, however, credit should be given to it's founder, Arthur Jones, and all the pains taking research he has done. HIT has been around for a long time.


This is why I don't blog about fitness theories - I get trapped by esoteric jargon. I am using the term high intensity training in the common sense of english usage. Training at high intensity - like Crossfit - vs aerobic training or pure strength training.

I am not talking about Arthur Jones theories and perhaps that is obvious if you read the original essay about Jason's Crossfit workouts which as far as I can tell has little specifically to do with anything espoused by Arthur Jones.

January 2, 2010 | Unregistered CommenterChris

why should I think that super slow reps are good, when that is about as unnatural as you can get? what moves deliberately slow in nature (besides e.g. a stalking cat)?

why should I think that fast reps are bad because they place too much stress on joints? why not say that going slow with too much weight causes too much stress? if you reduce the weight and go fast, why does that have special risk?

P.S. while people rightly say that almost everybody might be selling something, why not mention that Arthur Jones was in effect increasing gym profits by getting customers out the door as soon as possible - just like a restaurant getting its customers to leave a table ASAP so the next diners can sit and pay.

January 6, 2010 | Unregistered CommenterStarf

I think the exercise and diet issues are being combined in part because they both relate, one hopes, to feeling good. Not just not feeling bad or not being sick from Neolithic agents, but in terms of taking control of one's life and giving one the feeling of control over certain aspects of life, adding something positive to the negativity of avoiding the Neolithic agents.

In terms of exercise with free weights compared to machines, and compared to getting outside and taking a walk in the hills: in some sense just going to the gym and working out is, for some people, an end in itself, as part of feeling better and looking better, etc. I do not see that there anything wrong with that. I do strength workouts three times a week and play tennis three times a week. I enjoy both.

But it is certainly amusing to read the different theories, some with resemblances to angels on pinheads, regarding how best to do the work-out, when the reality is that simply getting out of the chair is probably the biggest and most important step (after avoiding fructose and wheat and PUFA).


I think to those of us who think diet matters more to disease avoidance than exercise, some of the more esoteric doctrinal differences in the training world look less like arguments about saturated fat than arguments about whether, say, lamb is better than beef.

February 27, 2010 | Unregistered CommenterRichard

Dr. Bernstein brings up a couple of interesting points regarding exercise. He believes that anaerobic is better due to the high glucose demand which ultimately causes greater insulin sensitivity for lowering blood sugar. This eventually reduces the body's ability to hold on to stored fat, thus lowering insulin resistance. He also encourages a strenuous form of cardiovascular exercise that is intermittently anaerobic. He points out that not only does this accomplish the same benefits to metabolism as weight lifting, it also promotes faster heart rate recovery (from maximum to resting) which he claims is the present day barometer for cardiovascular health. He also implies that doing this often has acquired benefits.

Do you agree with any of it and is it only relevant to those with damaged metabolisms.

KGH: Positive effects on insulin sensitivity are well known, yes

February 28, 2010 | Unregistered Commenterkb

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