Z2 power vs Z2 HR

So most of us here train to power for everything, but I’ve heard people talking about training z2 to HR.

However it seems like my heart rate z2 and my power z2 do not line up in the slightest (power z2 has me at HR z1) .

Yes ofc aware that HR is less reliable, but even then, when doing FTP work, this does actually line up.

Does this mean I’m doing my Z2 too easy, should it be brought up a notch? Or keep it in line.

Anyone here train z2 to HR, what are your experiences. Just curious

Not knowing at what HR or (current) power your aerobic threshold is, I would say yes, your Z2 is too easy. Also, it takes a while for your HR to rise so if your doing a long low Z2 ride, it will take a while before your HR starts to drift upwards (not forgetting hydration, heat and 1000 other things).

Or then you have just become extremely fit!

I do all my Z2 based of HR. I’ve listened to several pro coaches (Mattias Reck from TrekS., ISM etc… even Seiler) who all have said that endurance training should be based on HR. Of course I have my power target zones but it’s the HR that triumph.

My AeT is at 139bpm and current power at around 240W, which is almost 77% of my FTP (note Coggan Z2 is 56-75% of FTP). For my Z2 rides I will not want to go above the 139bpm, target is 135bpm.
E.g. for a 3h Z2 ride I would start of targeting 230-240W and let my HR get up to the 135 bpm target . If I have a good/bad day I obviously need to adjust already at the very beginning. However along the workout when heart rate drift occurs I reduce the power/pace/effort.

Others may be more obsessed with power (Palpatines, Anakin etc) :rofl:


On the trainer my Z2 is always hr in z1. Lower tempo is pushing my hr into Z2 zone. Everything above is in line with zones. Outdoor is correct. Do not care about this :slight_smile:

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Good to know, this is exactly my experience. So I’m not alone here. I was wondering because if I hold z2 HR it’s definitely a lot more fatiguing.

This has me thinking recently.

First there are multiple models for HR zones (and Power zones)…so you might want to clarify on that. Otherwise people might answer with different assumptions in mind.

I might be similar to you.
I start with Friel HR zones derived from threshold HR but adjust start of z2 and z3 by ~-5%. So these better match the RPE of the according Coggan power zones. Otherwise HR z3 feels way too narrow and HR z2 would let me produce too hard power. I look at HR as additional guide, especially indoors.

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No. It means you have a well developed aerobic system. Your low HR is a response to this condition.

Some longtime MAF practitioners (low heart rate training) have managed to increase their power @ MAF from Z2 to near-FTP. They now have to do their Endurance work at sub-MAF HR because it’s too much intensity if they do it by HR.

If you have a correct FTP, then stick to Z2 power/RPE and be done with it.

To add on that:
Otherwise I could leave Friel HR zones as is and then think that I’m super duper aerobic fit and while my power distribution is more pyramidal my HR distribution would then look more polarized.

Guess there might be some truth to that…being a bit aerobic fit…but not like those forum hitters doing 3-4 hours endurance with very little (or even negative) aerobic decoupling.

With my modification my HR TiZ is more in line with the pyramidal power distribution and “it feels correct”.

After all I guess it’s mostly more of a technical question for me.

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I’m a fan of Z2 HR for endurance training >3hrs.

I get that power is awesome for training. But I would never exclude the HR part of the equation. It helps me understand when my aerobic conditioning is good. Flat HR under threshold HR during high SS intervals or low threshold intervals, for example. Or consistent recovery interval HR, etc.

If HR was a pointless measurement for endurance training, then we wouldn’t see pro athletes wearing HR straps. Except…we do. Pretty much all of them. I’m going to trust the advice they’re getting is pretty good :slight_smile:

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I have both HR and Power in Z2 and do monitor both. I already know quite well, which gear, which cadence leads me to a stable Z2 training.
my power readings are rather unreliable so I tend to watch my HR closely, also to make sure not to go beyond Z2 limits.

I know about the HR being dependent on so many factors, but still I am surprised how low its value is seem at TR. i feel that with some experience in training everybody should be able to read the HR numbers the right way taking into account other variables like exhaustion, sleep etc.

FWIW here is a snippet from Training and Racing with a Power Meter 3rd Edition (page 34):

“Relating the specified power levels to corresponding heart rate ranges or zones is somewhat difficult to do owing to the inherent variability of heart rate as well as individual differences in the power-heart rate relationship (even when referenced to threshold power). Nonetheless, approximate heart rate guidelines have been provided in Table 3.1 so that they ca be used along with power to help guide training, if desired.”

In other words, don’t get excited if the zones don’t line up.

Only during early base, or after taking time off the bike. During that 4-6 week period of time, upper zone1 and lower zone2 power will map to zone2 HR (Coggan zones). I normally cap efforts at the top of zone2 HR during this time. For me, top of Coggan z2-HR is 9bpm lower than Friel z2-HR.

Coming off early base, my aerobic decoupling will drop below 5% and I start seeing a lot of 0-3% decoupling. From that point forward, zone2 power will usually map to Coggan zone2/zone3 HR, and map to Friel zone2 HR.

Not much later in base I can do threshold efforts with almost no decoupling. Seems that both cardiovascular and metabolic fitness is good, and I see stable relationship between HR and power from aerobic endurance to threshold. Tempo and threshold workouts map to the same Coggan HR zones. Overall I find Friel HR zones to more accurately map to power zones, mainly because of z2 and z5/z6.

After a few months of base I can ride all day at Friel zone2 (130-143bpm) without major fatigue. Coggan’s guidelines for zone2 (111-134bpm) would have me riding much slower and no difference in fatigue the next day.

Given all that, I’m happy training to power zones most of the year. That means I usually ignore HR zones and use power zones to guide training. I do look at power-to-HR relationship of every ride, and what I wrote above is based on 4 years of reviewing power & HR data of every ride/workout. I’ve got a pile of century rides both flat and mountain, many in lower to mid tempo (by intensity factor), and all of those have an average HR in Friel zone2.

FWIW my inside HR is almost always lower than when outside, and I train in the garage without air conditioning (or heat) so the temperatures are comparable.


I might be oversimplifying things, but think of this:

You can measure the effort you put in (HR)
You can measure the output of your effort (Watts)

Without any other reasons (and there are plenty, see Seiler et al.) I train longer intervals up to Tempo only by HR. Even at Threshold I check for HR anomalies.

Yes, HR is variable. But it is variable for a reason (at least most of the time). If I’m able to produce 10-20 watts less in Z2 today, then it is likely for a reason. Maybe I should not push to reach my goal wattage. With that mindest I have never gotten sick again for 2 years now. Not even a slight cold. (maybe just a coincidence or luck, but worth mentioning I guess)
Same the other way round… If HR is stable and RPE ok at 10watts above target … enjoy :slight_smile:

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I’ve been doing a lot of Z2 for base. I keep an eye on both power and HR. Remember that Z2 is a range. Low Z2 is very easy for me. High Z2 will generate some fatigue for me.

I’ve been trying to follow the Inigo San Millan protocols, so I calibrated my San Millan Z2 (LT1 aka aerobic threshold) with the talk test and my HR. With talk test I’m at the higher end of my Z2 and 130bpm. I use this for most base riding. I use low Z2 for recovery rides. I don’t even do much Z1 on trainer rides.