Additional Zone 2 Rides - best way to dial in Correct Heart Rate Intensity

As has often been suggested and discussed on the forum, the podcast, etc., I am currently on a SSB low-volume plan to which I add zone 2 rides for additional volume and zone 2-specific adaptations.

Many of the leading zone 2 researchers such as Seiler believe that it makes a lot of sense - for those of us not constantly measuring lactate levels - to not only look at power but also heart rate to dial in the correct intensity of zone 2 workouts.

The issue I have right now is that the workouts TR gives me seem to be too low in intensity as they do not/only barely get my HR into Zone 2 territory. So I wonder how to best handle this within the TrainerRoad cosmos.

Some more info:

  • based on the heart rate reserve method my HRZ2 ranges from 131 to 144 bpm (max HR-based it would be 135-147).
  • a few days ago I did Little Park as suggested by TrainNow. It had me ride between 50-59% of FTP, so below or at the lower end of most zone 2 power zones (e.g. Coggan starts at 56%). During this workout, my HR AVG was 120 bpm and maxed out at 129.
  • yesterday, I selected a “stretch” endurance workout, Navetta, which had me between 55 and 68% of FTP. During the workout, which has 3 peak “intervals” of 15ish minutes at 68%, I increased the workout intensity by 5% a few minutes into the second “interval”. This finally got my HR up to 130. During the third interval, I did even get it to 131 :partying_face:

Now, the first question is: how important is it that heart rate is in zone 2 and not below? My hunch is, that, in order to get the adaptations we are after, it’s at least preferable. But that’s obviously not empirical.

Assuming that my hunch is correct, the next question is: what’s causing the issue then? As I don’t feel fatigued (and my Garmin watch tells me that my current training load is in the optimal range :sweat_smile:). Thus, I think the simplest and most likely explanation is that my FTP setting is a bit too low*.

What’s the best way forward?

  • simply wait for my next AI FTP detection or
  • do an FTP test now?

And as long as my FTP (setting) is unchanged:

  • Should I expect that progression levels take care of this and simply pick suggested TrainNow workouts or

  • Should I keep selecting relatively “hard” easy workouts (talking IF and TR classification) and, if necessary, manually increase the intensity? (Making sure that power stays within my current power-based zone 2).

  • Or should I simply not care and enjoy the easy rides TR suggests without worrying about HR?

And bonus question: wouldn’t it make sense for TR to take HR into account for endurance workouts specifically? At higher intensities, it’s a less reliable metric but when it comes to zone 2, it seems like a useful data point to assess an athlete’s fitness (and so, e.g., could influence endurance PLs) and might be useful to select workouts / adjust intensity.

’ * I had like a two-month break from training in May and June, restarted in July with AI FTP detection (which did a pretty solid job), had another 2-week break due to travels, and finally restarted in August with another AI FTP detection. I assume this on/off training makes AIFTPD less reliable and I might be re-gaining my lost power from early this year a bit quicker.


Not very important. The fact you are exercising is more important. The endurance volume supports your harder workouts, and you’ll likely find an ability to progress your hard workouts more often, or have less failure if you’re keeping your z2 intensity lower.


This. You’re not a computer. Don’t look so closely at what your body is doing. Go by feel. Easy should feel easy, so it sounds like you’re doing it right!

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I’ve had a couple people say that the talk test is quite effective. If you can/could carry on a semi-normal conversation – you’re still in zone 2.

Sometimes during a ride, I’ll recite the Pledge of Allegiance out loud. It gets a few strange looks. But patriotism, you know.



Everything gained from “zone 2” training is also gained from every other training. It’s just that the dose/intensity response is different

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200w (1)


I disagree. You should be looking at what your body is doing, just not simply hr/power metrics…or use those to build a feeling/picture of what’s going on when combined with RPE and your breathing rate.

I also don’t think z2 should be easy. Easy to me means sub 55% ftp and kinda just spinning. Not a lot of pressure on the pedals, coasting downhills, could legit do it for 12+hrs continuously and be fine. Dedicated z2 takes some focus to always be on the pedals, always be working just a little bit but not too much, pedaling harder on the downhills to keep power and hr up but slow on the uphills to stay out of tempo. After 3-4+hrs you’ll probably start building a fair amount of fatigue and naturally want to ease off or stop pedaling when terrain allows, but gotta resist that urge.

Go do Hoffman in erg mode and tell me how it feels after 4hrs. Unless you’ve tapered for it, it’s probably not gonna be easy after the first hour or so. It ends up being kind of a dull fatigue in your legs that’s doable and doesn’t require a high breathing rate or hr, but takes some focus to keep the power/cadence up.





ETA: That article illustrates everything that is wrong with the Internet. Lots of vague/undocumented/patently false assertions presented as “facts” by somebody with (at best) limited expertise. Sadly, things are only going to get worse when this sort of pablum is picked up and regurgitated by ChatGPT and the like.


Lol exercise physiologist vs carpenter

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But he’s an orthopedic surgeon! He went to medical school so he should know everything. :slight_smile:

@ThomasE Howard Luks is just another self appointed lifestyle guru selling books, podcasts, supplements, and whatever else to the masses.

I’m fine with these types getting people off the couch to do some zone 2 on their Peloton bike but they don’t know squat about real training.


What is your HR zone2? When I first got started 8 years ago, I looked at several HR zone systems and here are my z2 HR ranges:

  • 128-142bpm Friel system
  • 110-134bpm Coggan semi-reluctant and loose recommendations
  • 114-131bpm BCF (British) system
  • 116-128bpm USA Cycling system

You know what I did? I went out and did some 8-12 hour climbing rides and figured out that I can “ride all day” without suffering around 130-142bpm. Which happen to align well with Friel HR zones. So thats what I use, rather than randomly pick some system.

Some other people I know better align with Coggan or USA Cycling.

I think its worth individualizing your HR zones, rather than blindly accepting a system. And then use HR as a reference rather than worry about it. Guide efforts on feeling and power, with an eye on HR as an indicator that something is off (dehydration, lack of aerobic fitness, etc).

Hope that helps.


Dude knows his customers:

How much exercise is needed to improve Zone 2 fitness? I have spoken with many elite coaches about this. These professional coaches suggest that 90-minute sessions are needed. If performance is your goal, then preferably twice a week. That’s hard for many to do…

Lol. Reminds me a friend who argues one can never lose weight by exercise alone and has to diet. His strong argument delivered with faksure intensity:

you need to train almost everyday up to a whole hour.

Noooo. Humanity.


Fair enough.

Tbh I didn’t do a background check on the guy. But the article mentions many of the aspects that I heard others - I assume more well-respected people in the world of cycling/physiology/endurance sports such as Seiler or ISM - discuss as well. For Example, ISM gives his definition of Zone 2 in this well-known video.

In there, he also touches upon several of the benefits he thinks are distinct to or most prevalent in Zone 2 training. In short, he states that it is the intensity level where you stimulate the mitochondrial function, fat oxidation, and lactate clearance capacity the most.

Of course, ISM is also only one voice/perspective. As I’m certainly not an expert in physiology nor qualified to critically challenge any of these claims, I’d be happy if you, @The_Cog, or anyone else for that matter could point me to some reliable sources that explain why, in fact, there are no/little Zone 2 specific benefits/adaptations.

I hadn’t seen that video before. My goodness… where do we start. The intensity at which the mitochondria are most stressed is vo2max (or greater if you isolate them) and not “z2”. He seems to be under the impression only type i fibers have significant oxidative capacity, when it’s been known for some time that type ii fibers can be just about the same in the sufficiently well trained. You also can’t always be sure what muscle fibers someone is recruiting as there is a big range in the population, plus recruitment can change for various reasons like fit, altitude, fatigue. I also wouldn’t rely on him for muscle physiology, as I recall a trainingpeaks article where he mentions type iib fibers… which don’t exist in humans, but we’ve only known that since the 90s so maybe he just hasn’t seen that data that’s been available for ~25 years. Besides, there’s no reliable overlap between fiber type and metabolic pathways (this is related to training status) which would change one’s interpretation of the lactate shuttle. What else… There’s no accepted universal definition of mitochondrial function, but his definition seems to revolve around substrate oxidation and fiber type rather than what I usually see which is measuring how much O2 that isolated state 3 mitochondria can go through (their ETC capacity, similar to vo2max). You also can’t really “stimulate” oxidative phosphorylation, which he seems to think is a signal to improve aerobic performance, when in reality if how much fat you burned (or lactate for that matter) made you better at burning fat, then we’d see massive endurance improvements in all keto/LCHF experiments, and we see equivocal or reduced performance. You can’t “game the system” with substrate oxidation because the system is designed to not be gamed this way. In fact, if substrate use were a signal for aerobic adaptation we’d know it by now, and it just plain isn’t. It would be pretty bad design anyway. What are the actual signals? Energy state, redox state, calcium, ROS, and more. And this is just a quick brain dump after only watching a few minutes of this video that’s as long as Return of the King.

On your original topic, there’s technically no such thing as the exact HR range (I would argue there’s no such thing as a threshold HR either), and this is being way overthought. Lots of things modulate HR like sleep, stress, stimulants, and things that don’t even start with S, like fatigue. Isn’t TR’s thing entirely power based anyway? This is almost always an issue when you start mixing training systems and expecting neat overlap.

Can’t prove a negative. But here, try this one: Similar metabolic adaptations during exercise after low volume sprint interval and traditional endurance training in humans - PMC


Hey @ThomasE, thanks for writing such a detailed question!

It sounds like you’re concerned your HR isn’t where it should be – here’s why we think that’s not the case, and you don’t need to be worried:

Power vs. Heart Rate

TR does not use HR data for any training zone because your heart rate zones can change dramatically from day to day due to external factors, whereas FTP is a more stable metric on which to base your training. Some days, you may not be able to express high percentages of your FTP, but that does not change the value of your FTP.

Endurance workouts too low in intensity

By nature, Endurance workouts aren’t meant to be challenging and raise your heart rate to levels like VO2 Max workouts do. Your RPE seems good, especially for SST/Threshold, which we think is more important/representative of where FTP is than trying to guess based on Z2 efforts.

That said, if you feel like they are too low in intensity you can always choose a Workout Alternate to change the Difficulty Level, and based on how you perform Adaptive Training will make the necessary adaptations to subsequent Endurance workouts.

FTP setting a bit low

I don’t think your FTP is set too low since your Post-Workout Surveys seem to be in line with how a workout should feel for higher zone levels like Sweet Spot and Threshold. However, don’t be afraid to manually adjust your FTP by 5-10 points and see how your workouts feel at that FTP. Adaptive Training will compensate after a few workouts if your FTP was set a bit too high.


Peter Attia is also a lifestyle medicine guru (one of the better ones). I don’t know what game ISM is playing inhabiting this world. Have we ever seen the coach of a Tour de France winner do this kind of stuff? Maybe ISM’s long game is a zone 2 book or to enter this lifestyle health and fitness arena?

In any case, they are speaking to the non-athletes looking for a reason to ride their Peloton bikes.

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I don’t think that the literature allows you to draw that conclusion. In fact, quite the opposite, i.e., the largest increases in mitochondrial respiratory capacity have been found in studies with the most intense training programs.

Because (seriously!) there is no such thing as “zone 2” (or zone 4, etc.). Such distinctions, while sometimes useful, are almost completely arbitrary. In point of fact, exercise responses and adaptations reside on a continuum, and you have to go well up the intensity spectrum before things might start to change significantly. Even then, since recovery is essentially a 100% aerobically-fueled process, you will actually elicit the same adaptations by performing really high intensity, short duration intervals if the rest periods are kept short enough.