Zone 2 training. Power vs heartrate

Just a little confused. I have been trying to build my base and have been trying to stay in zone 2 on my rides. I am 51 and have set a maff zone 2 heart rate of 129.
I did an outdoor ride with a buddy this past weekend (proper social distancing in effect) and managed to stay in HR zone 2 for most of the ride. This is from my 4iiii’s left side meter.

As you can see heart rate was pretty good and I was satisfied and then I looked at my power and it was all over the place. Should I be trying to stay in zone 2 power the whole time?
I am approaching a ramp test next week so all my indoor rides this week are zone 2. Here is from an indoor ride.

So I have been concentrating on heart rate but I am thinking I need to have both my heart rate and my power in zone 2 to be really working on zone 2 base? Is this correct? This is the first year I am training outdoors with a power meter.

Thanks for the guidance.

I’m not aware of any science on this, someone may come along and provide that.

My experience had been targeting power.

I wonder if something is wrong with the calculations. If you truly rode at MAF heart rate then how could you possibly accumulate 42 minutes in Z4 (threshold), 12 minutes in Z5, and 4 minutes in Z6?

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42 minutes seems high but not impossible.
In a 3 hour ride all those mini spikes into Threshold power won’t necessarily result in threshold HR.
Although if you add the Z4 - Z6 together that does look like something is amiss.

What are the HR zones based on? HRmax, LTHR, something else?

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PS. Heart Rate zones tend to typically be a zone under the Power zones for most well trained people.
For example Power Z3 ends up with HR Zone 2.

I think Tom Bell might have wrote something about this?


Heart rate control is normally what I would target for a long Z2 ride, not stepping outside the endurance zone. Terrain can sometimes dictate your power too much. Avg and NP can be a good insight to how you were riding over 3/4 hours, but I wouldn’t be staring at 3second avg power for endurance rides.

After all it is the heart and blood you are trying to train which reaps the most benefits. There is no point doing 200w endurance if you are at Tempo HR.

I get you point but if you are in Endurance power zone you are not going to be in Tempo HR unless overheating / dehydrated. If someone is in Tempo HR I’d suggest they are actually riding in Z4 power.

Thought it was a Tom Bell article…
“Note that there isn’t a 1:1 correspondence between these heart rate and FTP zones. We often find that the heart rate zones come out a bit higher than the FTP zones, so riding at zone 2 power, might only result in Zone 1 heart rate. For this reason, we tend to err on the lower end of the heart rate zones, especially if the goal of the session is recovery.”



You sound surprised that the power readings are “all over the place” when riding outside. That is what happens if you don’t keep an eye on your power readings when outside, especially on a hilly course but also when riding with others.

I set a target HR for the ride and if my heart rate drift a little upwards I just ease off the pressure on the pedals ever so slightly. If HR is a little low I just put some more pressure on. In the end there might still be some work done in z4-z6 but not much and certainly not for more than a couple of seconds so it doesn’t influence HR. I usually end up with the majority of the work in z2 but also a substantial amount in z3.

It takes some focused work to keep the power steady so keep one eye on your power readings and one on your HR and get a feel for how much pressure you need to apply to reach your target HR. It might be a good thing to practice on a solo ride; it is difficult to get a steady power when riding with others.


For the last seven years I’ve ridden the endurance days by feel and breathing. Power will go into zone 3 or 4 for some short hills, but HR stays fairly flat for most of the ride, and for a 2.5-3hr ride decoupling will be under 2-3%.


Isn’t most of the improvement in exercise performance with training due to changes in the muscles themselves?

And why would slowing down to reduce your heart rate result in a greater training effect on the cardiovascular system - just because you might be able to go longer, you mean?

My guess is that your ride was rather hilly or had a lot of stop-and-go or coasting. Heart lags behind power by quite a bit, so it would have stayed in zone 2 while your actual effort was all over the map.

No, Zone2 rides are targeting adaptations in the muscles. For example from the site referenced above:

Assuming good hydration/fueling/temperatures your HR will increase as Type 1 slow-twitch muscle fibers get tired and more Type 2A fast-twitch get recruited. That increased HR lets us know that the training is sending a signal to the body to adapt and:

  • increase mitochondria (more power generators)
  • increase use of fat as fuel source
  • increase fatigue resistance
  • increase aerobic function of type 2A fibers

In other words, increased HR is a sign that we’ve started to ride long enough in zone 2 to begin sending adaptation signals to the body. It’s a good thing, embrace it and ride long.


Heart rate zones I am using
Zone 1 87 to 105
Zone 2 106 to 129
Zone 3 130 to 152
Zone 4 153 to 163
Zone 5 163 to 174

Maff rate 129

Todays ride trying to concentrate on zone 2 on power meter. I had one big hill that is a strava segment and could not resist pushing it half way up.

I find it very hard to stay in zone 2 power wise. I think I will just ride for mainly enjoyment and fun outside and will keep to my indoor workouts for training. Any riding outside structured or not will be a bonus.

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Post your ride, in TrainerRoad or some other analytics software like TrainingPeaks, etc. and set the privilege so that it’s public. Let’s take a look at this data in more detail.

Is the indoor ride using the same power meter?

Outdoor ride 2

Outdoor ride 1

Indoor rides are done on a saris h3 and the saris is used for power.

Outdoor rides are on a 4iiii’s meter left side only.

The power meter difference is part of it.

The May 16 ride looks fine. The May 10, does not. The ride has a IF of 0.79 Your HR is also a bit higher there. I’m going to go out on a limb and think your HR zones are off. Did you do a 20 minute FTP test? What was your avg HR on that 20 minute?

Your HR is also surprisingly steady. On that May 10 ride, you also have declining cadence, indicating fatigue, but the HR is fairly steady. At threshold efforts, your HR is only about 20bpm higher than your Z2 efforts. I’m thinking you’re similar to Lionel Sanders in that regard.

I also think that MAF formula is bogus. Determine your LTHR from a long effort. Either the 20 minute FTP test or the longer 1hr+ test.

Edit: I’m going to take a WAG that your LTHR is 140bpm-ish with a max around 165-ish.

Edit2: Also a good listen, not exactly the answer, but it’s good info …

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What’s wrong with his May 10th ride? It looks like a solid level 2 effort to me. The IF of 0.79 is right in the middle of the expected range of 0.75-0.85.

Why would you always try to keep your power in level 2? It seems that would require riding really slow up hills, then bombing down them at a moderately high effort. Nobody I know actually rides that way¡