Last year I used a Garmin Heart Rate based training plan. This year I bought a power meter and started using TrainerRoad. Garmin had me do a lot of 2 or 3 hour rides in Zone 2. I am on a low volume plan and then the last 2 Saturdays have gone for about 2 hour rides trying to stay in Zone 2 like last year. My normal 2 hour route has a couple decent climbs and I can usually climb them slowly enough that my heart rate barely creeps into Zone 3 for about 1 minute, but I noticed my Power Zone went up to 7. Should I be trying to keep my Power in a certain Zone on Endurance rides and completely ignore my heart rate now that I have a power meter, or is it still beneficial to do Zone 2 heart rate riding?
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Long story short, you need to establish both HR zones as well as Power zones.
For example, my z2 is up to 220w, but thats the theoretical max (first lactate threshold measured by lactate testing), but if I were to ride 220w constantly it would be a lot of fatigue, so I try to aim for 180-220w when riding outside and that usually ends up being 180w avg power, and about 190w NP.
Some days those rides mean I am 10-15 beats under my z2 HR “max”, but some days I am a bit higher. So for those endurance rides I look at both HR to gauge effort and whatnot.
So, I would say that you need to establish your zones based on a ramp test or the like.
And to be very clear, TrainerRoads endurance rides (like Petit) can for some be on the high side of endurance power watt wise.
I am a anaerobically inclined athlete so my z2 power is lower than what TrainerRoad would put me at with my FTP (305 ish).
If you know your FTP, aim to have a Normalised Power of about 0.55-0.65 for your endurance rides 
Gives you those mitochondrial adaptations while still keeping the strain of the body low enough to be able to ride a lot.
Also don’t forget to fuel your z2 rides as well. 90min or below is fine without carbs if you have eaten properly the day before and morning of, but anything over 90min aim for 60-80g of carbs per hour.
This ended up being long story long, but yeah Its a very big topic when it comes to zones, how to train etc.
I think it crucial to keep track of HR and power and their correlation.
Good podcast on the subject of z2: How to find your “Zone 2” without using a lactate meter | The Peter Attia Drive Podcast - YouTube
And same podcast regarding volume of z2: Zone 2 Training: Dose, Frequency, and Duration | Iñigo San-Millán, Ph.D. & Peter Attia, M.D. - YouTube
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If Zone 2 HR truly yields zone 7 power either your LTHR is too low. Or your FTP is too high. Or some combination of both being off. Or your PM calibration is off. Assuming calibration is ok how you test becomes critical when comparing HR and power zones.
You could go out in one ride and establish both in one test as recommended by Joe Friel: Ride 30 minutes as if it were a time trial so as hard as you can go for the entire duration. For LTHR take the average HR of the last 20 minutes. For FTP take the average watts over the entire 30 minute duration.
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Thanks, this is awesome info!
I only hit the Zone 7 power for a couple seconds and it’s back down again before my heart rate climbs out of Zone 2, but that’s what I was wondering. Should I find an endurance course where my power never goes above a certain zone, or is it ok for my power to spike occasionally as long as my heart rate stays in Zone 2?
Don’t worry if it spikes a bit, but unless you really have to spike it it’s kind of unnecessary load since you’re doing endurance.
Fine if you go into tempo watts just to get up to speed for 2-3 seconds. But you shouldn’t be spiking into z7… that’s like a sprint.
Keep it easy on the easy days!
Just because there is a delay in HR doesn’t mean you can ride hard until it eventually goes up…
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OK I interpreted you held zone 7 a bit longer. Sounds like just new to looking at power…Power will naturally spike a bit especially if new to riding with power. Zone 7 is a bit high though. It might take a few rides but, you’ll have to learn what your zone 1, 2, 3 etc…power feels like. Once power is under control stop looking at your watts bouncing all over the place on your computer screen. Focus more on steady even pressure on the pedals. The tension or lack thereof in your legs. Your breathing…Also, smooth power readings by using a 3second average (or longer) rather than instantaneous.
Still might be good to do the power/HR test I referenced to get a baseline. Honestly though, if new to it all I’d just pick HR or power and train with one or the other. HR will be really useful for lower intensity rides but, not perfect. Power is amazing for HIIT but also not perfect. Learning to use both and incorporating RPE seems like the best compromise. All three are useful. All three have limitations. It’s easy for me to say as I learned before HR then learned HR before power. I can’t imagine getting into this sport now. Too much information IMO.
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Hr training at times can vary as a lot of factors like weather, humidity, hydration, sleep can sway it. While power is just power. I do still keep an eye on hr just to help me pace if it is hot outside doing an unstructured ride and useful for fitness gains.
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Yes, very good points! I know that in the mornings for example, HR is much higher and faster responding, than in the afternoon.
Don’t know if it is because its early, or I just had breakfast/coffee or whatnot. But morning commutes HR is always a little bit higher!
Like some others also say, you eventually get a feel for what endurance riding looks like, and HR can then act more of a compass.
Power is always absolute.