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Zone 2 training

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I wonder if anyone here is already practicing this kind of training.

A useful breakdown on zone 2 is in this Laura Norris website. Zone 2 is basically a heart-rate range corresponding to the plateau of serum lactate concentration, below the aerobic zone, a range in which the energy is mainly derived from fatty acids and which exhibits many metabolic benefits, mainly due to mitochondrial number and efficiency increase.


There are a few issues with zone 2 training, the first one is to determine the  HR range corresponding to such zone. Usually it's done by measuring directly (better) or calculating (much less accurate) the maximum heart rate, HRmax. Zoen 2 range corresponds to percentages of HRmax, according to various definitions.

Peter Attia suggests Zone 2 = 70% to 85% HRmax.

Other suggestions are listed in the linked webpage.

Often Zone 2 is calculated as 60% to 70% of HR reserve, a quantity estimated by formulas like the Karvonen formula, or the brute and very uncertain HRmax=220-age.

Also, according to Peter Attia a better estimator is to measure serum lactate, which should be in the range 1.5-2.0 mg/dL. More precisely, there is a lactate threshold value corresponding to a plateau beyond which aerobic metabolism is triggered.


Often, training zones are defined by percentages of maximum heart rate. However, methodologies may delineate the zones differently. 

  • The Norwegian Olympic Federation (and many research articles) define zone 2 as 72-82% of maximum heart rate. 
  • Dr. Stephen Seiler’s 2006 study on training intensity zones found that low intensity running cut off at 81% heart rate max in trained runners (+/- 2). This is the same as the NSCA recommends for easy zone running. 
  • In a study of training qualities that predict performance, Casado et al. (2021) defined easy runs as “62 to 82% of HRmax,” with minimal mental strain. 
  • Jack Daniels Formula defines easy zone training as 65-79% of max heart rate. 
  • The Joe Friel method using lactate threshold heart rate defines zone 2 as 85-89% of lactate threshold heart rate. (Some though use <85% of LTHR to calculate easy zone heart rate, if they are functioning in a three-zone training paradigm.)
  • Polar defines it as 60-70% of maximum heart rate. 


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Today, equipped with my new Polar H10 chest strap, I did a direct measurement of my HRmax. That was a brute force increase in treadmill tilt from o to 15%, then steady increase in velocity until I was afraid to drop dead on the treadmill. My HRmax turned out to be 177, perhaps I might have reached 180 but I chose to play it safely.

Applying the inaccurate 220-age formula, my HRmax would be 158, almost 20 bpms less than the measured quantity.

This is the graph of the test, time versus bpms, I did it in 2 stages, first time around I reached about 165, 2nd time around 177.


This is the output of the training session from the polar app connected to the sensor


After the test, my wife went: 'Since you are already sweating so much, you can hang the laundry'. Today it was under a scorching sun with high humidity, I recorded this chore as a training session, this is the result in the Polar app, which illustrates the training zones. I didn't adjust my HRmax so I don't know precisely the zone it might have been in lower zone 2 according to Attia.


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Next time around I'll try and hit a 70% HRmax pace, checking that the results fit the description of a moderately easy, possible-to-talk but inconvenient qualitative state. That's how zone 2 is described (RPE= Rate of Perceived Exertion)

They say that HRmax is different on different devices (treadmill, stationary bike, eccentric, rowing machine). I have a bike and maybe I'm going to test my HRmax on it but not very soon.

Peter Attia recommends, as a beginning level, 2X30 minutes per week of zone 2 training.

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It is a thin ice and since I personally do not like "excercising as obligation" (unlike many people who are completely ok with it) my intuition could be too biased against intensive excercises behind what is thought to be our evolutional tuneup. So I am completely ok to find myself "barking on a wrong tree".

So my concern about such excercising is that it could make more harm than bring benefit. Just excercising more than we are evolved to do and only in the context of longevity, not even health. All other contexts like medical prescriptions, health, internal and external recognition that drives the big part of athlets - all is out of scope, as always - it is a choice, a tradeoff that when done consciously is ok.

My orientation about "optimal" is 5h/day of activity with 1h of being considered as intensive but IMHO it is far from be intensive in proexcercising communities parlance. With some sudden bursts for 15-30 seconds but not every day and not for everyone. Like described here https://link.springer.com/article/10.1007/s42978-020-00091-0

So daily chores that spreads around the whole day, with 2h of walk and a short run, maybe a bit of calistenics is en entry to the way our bodies evolved to live but we do not really need to multiply it more than 2 times.

And another angle of view is an idea coined by Aubrey de Gray as "survival of the slowest". De Gray is obviously a genius but they are also error-prone so I am taking this idea as "a revelational guess" until it will be either proven or there will be a better idea)).

Nick Lane in the book about oxygene mentioned this idea as "supported by empirical data". Curious people, e.g. here https://www.quora.com/How-credible-are-Aubrey-de-Grey-and-his-SENS

seems agree with this. I personally read yet not enough papers/books to build my own opinion to what degree this is supported by the known data but there could be something like a requirement to work in the area and participate in research to understand it deep enough. I will learn it soon, I hope).


So what is my concern? If the SOS theory is in action, forcing body to speedup in the believe that it will create more mitochondrias/make them "more fit" will probably just force a negative selection from their population. Those already "better to be destroyed" will not participate in multiplication but will stay longer alive, producing more ROS and this way causing more damage. Since aging in such angle of view is all about increasing of mitochondrial inefficiency as an underlying cause of most aging-related things from the longevity perspective this is unwanted. However here comes a catch. I don't know how Nick Lane came to ~120 years as mitochondrial "hard limit" for out bodies but I assume he has some ground since he thinks about this area for decades and works on it etc, he definitely has better ground than I will ever do to make an educated guess on it. So most of humans are never hitting it close to this limit, hard to say if ROS damage is the main deep reason to die earlier or not. So maybe concern about SOS theory is not worse other benefits that intensive excercising creates.


That is my reason to rather use hunter-gatherers way of excercising and stay away of recommendations by people who like/biased towards intensive no matter what are their reasons (but if reasons are not grounded in science it makes their opinion less persuasive for me also).



Edited by IgorF
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Igor, I understand you because there should be some fun in exercise as well, zone 2 sounds like the perfect boring experience, although it is apparently where you reap the most metabolic benefits. And it should be paired with some VO2 max training (although the latter is subordinate).

I don't even know if I'll have the time to run on the treadmill for 30 minutes without interruptions, maybe by night but I already sleep little.

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Apparently, the concept of cardio zones was introduced by Sally Edwards in her 1996 book.


The original rationale has been adopted by the main heart rate monitor producers, like Polar and Garmin. So, zone 2 in my Polar H10 is 60-70% of MHR, whereas more recent research seems to pinpoint a little higher percentages. Also, there are many definitions of zone 2 .

Peter Attia uses the lactate concentration which should not exceed 2 mmol/l. This follows the classic definition of lactate threshold (LT)

Aerobic exercise, anaerobic exercise and the lactate threshold

Affiliations expand


All exercise draws first on intramuscular stores of ATP and creatine phosphate; initially these are replenished by anaerobic glycolysis. The lactic acid produced contributes to the rapid development of fatigue in high intensity exercise. Aerobic metabolism (at first mainly of glycogen, later increasingly of fat) is the principal route of ATP resynthesis in activities lasting longer than 2 min, but can only maintain work-rates about 1/4 of those possible in very brief bursts. Blood lactate rises at the higher aerobic work rates. 'Lactate threshold' (LT: approximately 2 mmol/l) is almost exactly the speed at which endurance races are won, and close to those apparently providing optimal aerobic training. This training, predominantly of muscle aerobic capacity, elevates LT more than maximum oxygen consumption. LT is not now thought to indicate oxygen-deprivation, but intracellular adjustments driving oxidative phosphorylation faster. Ventilatory breakpoints, formerly considered to indicate LT, correlate more closely with the accumulation of potassium than lactate.



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I listened to more podcasts from different sources and indeed there is some confusion about the HR range corresponding to Zone 2 as defined in sports physiology: the intensity of effort at which hematic lactate reaches a plateau of about 2 mmol/l.

Without a lactate-measuring device, I proceeded to triangulate HR as a function of HR max and rate of perceived exertion.

 According to today's test, my Zone 2 may be located at the border of Polar's zones 3 (green) and 4 (yellow), which are also the original zones of Sally Edwards.

That means about 80% HR and maybe a little higher, coherent with the indications of Peter Attia (from 70% to 85% HRmax) and more than the usually suggested 60% to 70 or 75%.

The workout may sound very boring but at the beginning is fun, trying to fine-tune the speed and tilt of the treadmill to keep a constant HR (in my case, 142 bpm).



Edited by mccoy
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  • 4 weeks later...

I'm doing just the minimum (even less) recommended effort, but the system efficiency starts to improve, producing more work with the same bpms. In my case, the average treadmill velocity increased, keeping the same 80% of HRmax. This is the typical graph of a zone2 session, a few warmup minutes, then trying to keep a constant HR by adjusting the treadmill parameters (velocity in my case).



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  • 2 months later...

an interesting talk with Andy Galpin on muscle endurance training and a lot of surrounding things, so-called breathing gears instead of (imho) more hype-driven than solid grounded zones+fancy devices advocacy



(Huberman's using of longevity word here is not in max lifespan context but rather in h&w industries context, but nevertheless the talk is interesting and actionable somehow - e.g. how not to stimulate unwanted muscle growth)


Edited by IgorF
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Thanks for the link. What I'm noticing about zone 2 in the narrative of Peter Attia or worse Inigo San Milan is that it may not be the best choice for everyone. The negative aspects are that It needs lots of time. It may worsen muscular or joint pains. It necessitates an uninterrupted gig longer than 30 minutes, longer than 60 according to San Milan.

It is good to know that it may be the ideal endurance exercise for longevity, but it sounds too inflexible, especially in the words of Inigo San Milan (various podcasts available in the web), who is after all a trainer of professional elite athletes.

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