Zone 2: Differences in Calculation Methods & Potential Benefits

I have been following the z2 discussions. It is interesting to see the variation in z2 ranges being discussed in various places. I see as high as 80% of max hr being noted as still zone 2. Can you help clarify what the range should be and why so much variation from various sources


Excellent question. I have been studying this for the last 10 years or so. There for sure bigger experts than me, just I know a bit about this. I think the main source of confusion comes from different people being different. So theoretically if you are training and your HR/avg power is increasing then you are achieving the primary goal and the rest does not matter. But there are many values that can be achieved from “zone 2.” First let’s be clear “Zone 2” is not Zone 2, just a nice name for it.

Benefits or potential desired benefits of "Zone 2"

  1. Aerobic improvement
    a) Improves mitochondria
  2. Become a much better fat burner
  3. Minimum stress on the body (allows more training)
  4. Improved health (longer discussion)
  5. A solid part of periodization that improves seasonal gains, giving a rest period
  6. A solid base allowing more intensity with less risk and downsides
  7. Improves work capacity (the amount of effort you can do in a week)

So when talking about this “Zone 2” you have to understand which of these benefits you are shooting for. Most people are thinking primarily about #1. In this case it’s possible you could do sweet spot or threshold workouts and see benefits, even vo2max might show improvement in HR/power…

Now the down side is at these higher intensities the aerobic improvement will likely end much sooner and result in a lower maximum benefit. If you nail your Zone 2 right you may see continued improvement for a long period of time. If you do zone 2 for a long time eventually you could get to the point that you can do sweet spot power zone at closer to a zone 2 heart rate so you can go fast for a very long time with little pain.

I would argue #2 might be the biggest benefit and bring all the other benefits with it.

So all that said I did not really answer your question :slight_smile: I will slightly answer your question now and answer it in more detail later.

Most experts like to associated this Zone 2 limit with AeT (aerobic threshold). That can be 65% in some people and might be 82% in others (I am not sure the maximum). So 82% has nothing to do with zone 2 heart rate. Seilers 3 zone model in this case is a better definition and let’s call it upper zone 1. Zone 2 is a convenient and now “standardized” name and roughly equates to where you should be training.

So when hearing the experts talking there is a disagreement of what AeT feels like or how to measure it outside the lab. I believe this is because it feels very different in a pro or elite vs a beginner. Maffetone was the first one to really bring low heart rate “zone 2” to the mainstream.

Maffetone mostly had runners and triathletes, and that is who mostly got excited about it, because they become desprate for a solution to their over training problems (less of a problem in cycling). Still I and many others believe Maffetone is still THE EXPERT when it comes to understanding average people (as well as top endurance athletes), in regards to low heart rate training. Low HR training gets a bad name because it sounds so slow, Zone 2 sounds a little faster and less scary :slight_smile:

So Maffetone has had hundreds of thousands of followers using or that used his program and I would guess 90% see the benefits (following all his groups for a long time). His HR limit is based on the 180 formula. You can google it Maffetone 180. For most people it seems to come around 65% of max HR but you could just use his foruma as long as you are not approaching or over 65 years old, where his formula stops working.

The main point Maffetone makes is that it is better to start on the low side of your AeT rather than risk it by going over. Going over can slow progress drastically. Being under your limit seems to have no negatives other than you have to run/ride so dam slow in the beginning, uphill you might even have to walk or get passed by the walkers… slight exaggeration. Finding a good route or doing z2 indoors makes it much easier.

Anyway that’s a quick summary. I will try to respond in more detail :slight_smile:

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San Milan, Peter Attia and Seiler seem to set the limit based on how you can talk but I think they are using themselves or serious athletes and so their talk test might be higher than the average person. They set it based on when you can talk but are slightly struggling but you can still have a continuous conversation but if you were on the phone people would notice you are exercising. For me and based on Maffetone’s limit’s it’s lower than this. I believe it is closer to when you first start to feel breathing feel more intense than an easy walk but talking is still unobstructed.

Ultimately I would say it’s important to know your self. For most people when they first start 65% or even 68% of max HR and strictly staying under it, it’s painfully slow except in optimum conditions. After a few months it’s much faster but those first few months are hard. So if you can’t handle this. Doing it indoors is much easier (with big fans and practicing deep breathing). Otherwise outdoors you might need to try these higher intensity levels and see if they work for you.

Overt a period of time I would think your AeT improves although based on Maffetone’s calculations he believes that takes a few years and gives about a 5 beat improvement. But this 5 beats combined with being faster at a low heart rate could give you up to 50% more power at an easy pace or more. (Just a guess).

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I’m confused now. I’ve listened to San Milan as my reference on this subject and have thus been exercising z2 based on the perception of “conversation with puffiness” guidance. I’m almost 65 and this perceived z2 lands me at around 75% max HR. Am I doing this wrong?

The problem is there is no clear answer (other than potentially a lactate test). After lots of Maffetone reading I believe that San Milan’s breathing indicator is slighly high for most of us, but at the end of the day if you are seeing progress in HR vs power then it should be fine.

Another indicator according to Maffetone is you should have as much or more energy after the session as when you started even when doing many days per week. Meaning it should not require much recovery. HRV monitoring should indicate you are are not digging any holes even after back to back days unless they are really long or you are noticably increasing your volume you might see a small hit.

If you are not seeing consistent monthly progress then I would reduce your target HR and focus on pre-ride food and getting enough sleep.

Generally I think 65%-75% is probably the normal AeT for most, if you have been consistent for a long time doing a reasonable # of hours per week then 75% might be closer to your actual AeT.

San Milan does not give much specific advice. I haven’t gotten much out of his interviews.



Agreed but he doe’s slightly suggest in an interview with Peter Attia a right under harder breathing threshold which is too high based on Maffetones suggestions. Because he is cycling focused and Pog’s coach people seem to take what he suggests more seriously.

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There’s a more recent podcast called The Proof, hosted by an Australian named Simon Hill, where he and San Milan discuss the perceived exertion of Z2. This has been my reference. One thing is clear. You can’t mathematically define it with a simple algorithm. I’m starting to believe that a lactate meter is the only way but I’m not willing to go that far :joy:.

I’m not so sure that level of precision is required unless the cyclist is very serious. The idea is to stay below the point where you start to cause a stress response from your body.

The breathing test, Maffetone suggestion, Seiler’s 60% of heart rate reserve, etc… are all “get me close” type ideas. The concept is to log hours and build up your aerobic endurance.



I agree with Dave, lactate meter is un-necesary. I did buy an SMO2 meter which works for some people, it clearly shows my defection point exactly where my breadth estimated AeT is which is where Maffetone’s 180 formula puts me. He says his formula is not good for 65+ years old. For me this is the place where breathing just barely starts changing, which is not the same as what I consider right before heavy breathing. It’s like the very bottom of a change between zero breathing and some breathing. It’s less than Peter Attia would suggest that you would notice I was exercising if I was on the phone. Also there is zero risk from Maffetone’s perspective of being slightly on the too low side of things.

I also agree with Dave, it’s the no-stress point.

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But I think we can all agree that there are variables in play that make Z2 unique to everyone.

I read Maffetone’s intro book last night and it all makes sense. There is an adjustmet for > 60 years old which would put me somewhere around 121 BPM at my tender age of 64. I’ve been working Z2 closer to 126 BPM so not a substantial difference and quite frankly, let’s not forget that it’s about maximizing fat burn (while still burning glycogen as we do at every category of effort). So I am happy to dial back my workouts but I think we can all agree that it’s not ever going to be an exact science.

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Yes, I think the exactness comes in the testing. If you are improving aerobically then all is good. If not, probably need to make some tweaks. If you get a pattern of long improvement and stop even trying all the tricks then you probably could switch out of “base building.”

Maffetone says some people just doing strength training a few times a week might block their aerobic progress (especially if they have a lot other stresses). I think strength training is very important. Indoor cycling and running can be perfect activities for testing.

I am actually just re-entering the world of high consistency (1 month of 6 days a week now), first time I have been this consistent since our twins were born (stressfully early) but still doing low volume but I want to start this testing process again. I have been doing a big mix of non-testable activities (MTB with kids…) but getting back on the indoor bike now so just did my first test myself. My HR reaches targets in about 10 minutes so I am just taking average power from 10-20 minutes. Not exactly Maffetone’s suggestion but I think it should give me a pretty good idea. I might not do longer than 20 on indoor bike so trying to keep it simple easy :slight_smile:

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