Z2 power question

I’ve been riding about 6-8 hours a week unstructured all year, but have just started to add in structured training on the trainer with the colder/darker days. My goal is to supplement the indoor intervals with Z2 rides on the weekend outside if it’s not too cold. I am confused about Z2 training (sorry if this has been beaten to death.) I went on a short Z2 ride yesterday. Heartrate was firmly in Z2, NP was right at the top of Z2, RPE was easy, but my power definitely slipped into Z3 and above. I live in a hilly area, and power definitely spikes on some hills as my FTP is very low. Is this ok for a Z2 ride or should I ride easier?

I’ve included the intervals.icu graphs of power and heart rate below (hopefully these show up).

Thanks in advance.


For endurance rides, zones based on power and HR are approximations. And given you ride in hilly area I would suggest widening your idea of “z2” to endurance at say 65-82% FTP (an example, not a prescription) and accept that you will go over at times, up hills, and go under at times, downhill.

Zones don’t always match, so don’t expect power and HR to align perfectly. Also, Intervals uses Friel HR zones and for some those are too high and you are better off using Coggan HR zones. There are other HR zone systems.


Before anything else I’d suggest reassessing your FTP by whatever method you prefer and resetting your power zones, and/or your threshold and max HRs and your HR zones.

The two graphs you’ve posted suggest (to my untrained eye, at least) that something is awry, in that you’re doing a fair bit of work up near threshold without your heart rate getting near the levels I’d expect.

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going into z3 isn’t the end of the world, but you’re not really “brushing” into z3 you’re spending 1/4 of your time there.

in general don’t try to be “top of” z2, its far better to be in the center or even bottom since you’ll end up getting less fatigue for a similar amount of adaption

some questions:

  • is it the default HR zone calculation, or have you tweaked them to you personally? HR is incredibly variable
  • when was your last FTP test, and what method?

I set max HR based on the highest HR I hit this year (may not be the best way).

FTP is just set using intervals.icu estimating it based on my ride history - probably not the best way.

The Friel HR zones used by Intervals are suppose to be set by going out and doing a 30-min all-out time-trial effort by yourself. And then taking average HR from last 20 minutes as your Lactate Threshold HR (LTHR).

Both Friel and Coggan HR zones want you to use LTHR instead of MaxHR.


Probably worth listening to the latest empirical cycling episode (10m tips 25) he goes over a lot of what is being discussed here.


If It’s not sustained threshold, then there is a lag for heart rate - so if you don’t stay there it takes time for your heart rate to increase to threshold levels.

To the OP - just use RPE - don’t get bogged down by HR or power. Go as hard as easy feels - hills or not. If your NP by the end is around 55-70% than you’re good. Technically Z2 goes up to 75% of threshold - but for me to ride for a few hours at 75% FTP would be fatiguing. After doing endurance rides for a few weeks/months you can get a feeling when you are working too hard. Just keep it below this “feeling”. The whole idea is that you won’t get too fatigued to give the harder workouts your “all”.

Good luck


Sure … but there’s a chunk of VO2 Max and Anaerobic as well. Unless it’s a series of very short, spiky efforts, it just seems unlikely, and at the very least worth a sense-check. :+1:

TL:DR: use your gears and keep a steady effort that FEELS easy at all times, even while accelerating.

For most endurance rides, I want to see:

<25% in zone 1
<10% in zone 3 or higher
Minimal time above threshold
Minimal coasting time
Few/no very short breaks

The time above threshold can be tough for newer riders to “get” because they’re not used to using their gears or they feel like they have to get up to speed quickly. If you go for a 5 hour ride and there are stop lights/signs along the way, the quick bursts to accelerate back up to 18-20mph from a stop add up. Use your gears, keep the power down while you accelerate, and you will generate a lot less fatigue on your long rides.

On hills, just be willing to let your speed go way down and make sure you have adequate gears.

On downhills, sit UP as big as you can get and keep pedaling. (Sometimes I even pedal while braking, but that’s just kinda silly, really).

Or, preferably, just pick routes that make steady power easier.


I live in a very hilly area, and have pretty much given up trying to do a zone 2 ride from my house. I can drive to areas that are less hilly to do such rides. If I ride from home, my power spikes over 300 watts in my lowest gear just to get up to the main road from my house. My FTP is just shy of 200 watts. Rides from home are for enjoyment and saddle time. At my age (68), I ride for enjoyment anyway.

I am about halfway through the latest Empirical Cycling Podcast - but it answers your z2 question very well.


I did an endurance ride yesterday - and to avoid cars and take a path that goes along a busy road there is a VERY short climb that hits 18%. Even with low gears you’re gonna go above threshold - but for about 5-10 seconds. Just happens. I can not avoid hills where I live - I just gear down and try to keep it chill, whatever my power is it is. But I’m in my lowest gears trying to go easy.

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I’ve recently adopted the opposite approach; Z2 during the week on the trainer where it’s easy to hold power/hr and long outdoor rides on the weekend with lots of Z2 but steady efforts on the climbs and let the power go where it needs, often SS & Z4. This just seems to fit my lifestyle better and the kind of riding I like to do this time of year.

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Only if your threshold is below 200 watts or so, or your gears aren’t as low as you think.

What if your ftp, like mine, is 2.9W/kg? And lowest gear is 1 (33x33).

I just looked and at 75 kg I hit 328 watts at the 18% crest of that bump (at 300 watt FTP) 34x32 low gear.

That is after four hours and trying to keep it endurance pace.

So……it’s hard to stay under 200 watts at 18% at my weight.

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I’m my opinion, if your goal is Z2 for the ride then just shoot for your avg power / NP to be Z2. I also live in a hilly area and I’ll ride up to maybe 80% ftp if it’s only for a few minutes. Drifting up in power is nbd, just don’t throw in a hard interval up it or anything.


This is good advice :+1:

I’d add a few things:

  • Unless we are talking about really long endurance rides (4+ hours), make sure you can recover from your endurance ride within one day. That is absolutely paramount, you want to be fresh for the next hard workout.
  • Avoid power spikes. Roll power on slowly whenever you can.
  • It is mostly about smooth, consistent power, you want to train your cardiovascular system and your energy supply systems. You want to minimize stress that causes additional recovery. So like @WindWarrior wrote, it is less about dipping into Z3 to get up a small hill or incline and more about not overly taxing yourself.
  • Route and bike choice is king. I know I cannot stick to my power targets on certain routes. Some routes have hills that are too steep, others have segments that are too tempting. Avoid those, make it easier for yourselr, not harder.

If you can’t avoid that climb, then you gotta do what you gotta do. But if you can avoid it by going a different way, I think that’s better.

I will always choose a no traffic option

Z2 less important than safety IMO.

And I think ppl are taking this entire premise too seriously. Keep it easy, recoverable (like you mentioned) and don’t smash the intervals.