Heart Rate and Power at LT1

For people that have done lactate testing and know their HR level associated with LT1 (which I understand is relatively constant), how do you distinguish between:

a.) A genuine improvement in fitness, at same HR you can push X more watts. Or at same watts your HR is a lot lower.


b.) Your HR is lower for the same watts in the context of accumulated fatigue from training.

I’m asking this because these days I can push the same endurance watts I was doing 2-3 months ago, but my HR is 10 bpm lower. This is not day to day HR noise.

Am I supposed to increase my watts to achieve the old HR level, or this is just an ephemeral effect product of accumulated fatigue?



Haven’t done lactate testing but have opinions. For myself, it’s the top end that gets blunted. But my coach says, “if you want to lower HR then I’ll have you do some back to back 20 hour weeks” (I can only sustainably recover from ~10 hour weeks).

I hope you get some athletes chiming in with HR and %FTP numbers for their LT1. It’d be super interesting for generalising.

To your point though, wouldn’t you realistically test your LT1 level to find out if the Power has increased?

I was very curious in the idea of getting a Lactate Meter. Pretty spendy still though.

With this, he is implying that is just an artifact of fatigue and not a true fitness improvement….

My understanding is that the hierarchy is: Lactate > HR > Power.

Seems like Vo2 max block after the back to back big weeks is a good complement.

What does this mean?

Does LT1 HR relationship remain constant and Power changes with fitness? So once you’ve measure Lactate, you can reasonably expect LT1 to occur at the same point?

Yes, this is what Mr. @sryke reports.

It’s a joke. I can temporarily drive HR down by doing a few big weeks. FWIW I’ve posted power @ my “all day HR” (~140bpm top on Friel HR z2). Basically it went from 150 to 200W over two years under my coach. Round numbers.



Very keen to see if people have tested (either self or lab) results to illustrate LT1 HR (%max or %LTHR) and LT2 HR (%max).

Something similar for me. No coach. No structure.

His classification is just a license to do tempo under the Z2 label.

Whatever. I can ride 8-12 hours at that HR. Sorry for stopping by and commenting. Later.

No, you should train according to power zones and leave heart rate as a secondary metric. Heart rate is influenced my many things, including fitness, fatigue, sleep (quantity and quality), illness, etc. Apart from pacing mellow endurance rides, I do not use it as a primary metric.

To address your questions, though:

  • Yes, it is normal that heart rate in a specific power zones decreases as fitness increases. So if you do lots of endurance rides, your heart rate in Z2 will tend to be lower. 10 bpm jives with my personal experience.
  • Not just heart rate in absolute terms is important, but how your heart rate changes over time. E. g. if you are doing hard intervals (threshold, VO2max, whatever), how much time do you need until your heart rate goes back into Z2? When I am trained and well-rested, it is <90 seconds.
  • There is typically no simple way to draw conclusions from a single data point. To me one of the most useful metrics for how hard a workout is to look at the heart rate recovery time (see previous point) and how that develops as I do more and more intervals. The first one gives me an idea of my overall level of fitness, they give me a baseline. If my recovery time explodes, I know I might have to push hard to finish the workout or call it quits.
  • Heart rate lags behind and is not useful to pace shorter efforts.
  • Heart rate is highly personal. Some people have a higher heart rate than others in specific power zones. It doesn’t mean they are more or less fit, just that their heart has adapted differently to the demands.
  • HR is useful as an additional, secondary metric to inform your training, but not suitable as a primary metric if you have power data.

No, lactate heart rate changes with fitness, too. It is just that your heart rate range is much narrower and don’t change as much as power zones might. In my case, heart rate in specific power zones can change by 10–15 bpm.


My two cents: Over a medium-long period, an improved pwr/hr relationship very likely means increased fitness. Provided that perception of effort or rpe agrees.

Over a short period, it could be fatigue driving things. I experience this a lot, hr sinks thanks to load as it were But then we have perception of effort to double check. If the same wattage creates a lower hr but feels harder, fatigue is probably the main driver (which doesn’t rule out improvement, just that for the moment the fatigue effect on hr dominates).

Would not worry too much about increasing Z2 watts as such as long as Z2 rides are in the zone and facilitate overall training goals. Conversely, if upping the watts does not interfere with other rides, no problem going for it as long as you stay in zone.


This is the key. Thanks for your comment.

Can you ride 8-12 at the power you associated with that HR?..…I’d like to see that 7000 kj ride file :eyes:

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I like this thread.

I’ve been training for about 1.5 years now. In that time ive learned (and I keep trying to apply this knowledge) that heart rate is a bit limited when trying to assess fitness gains.

Hard blocks of volume and will drive my heart rate lower. “Suffering,” having a huge mental aspect, can correspond to that RPE and tell me it doesn’t hurt because my heart rate is low. It’s fine at Z3 and Z2, but higher than that when the heart rate doesn’t rise to meet the demands the RPE goes up.

Adding to this, the Garmin watch I run concurrently with my KICKR, “rewards” me with a higher VO2 max score when I’m fatigued! Take a rest week, heart rate rebounds, and Garmin tells you that you’re now “unproductive” and lowers your VO2 max score. Very frustrating. I know, just a number, but let’s be honest, we live by these numbers and ignoring them is much easier said than done. For all of us.

I’ve been tempted to hide my HR info and just go by power and feel.

Pretty sure he meant in a week.

You can also see the entire existing thread about lactate testing data here.

I think is not so fine at z3, z2 either, because you want to keep the work within the target zones, otherwise you dig a big hole in big rides.

I disagree here, the HR/Power relationship is one key marker of performance.

It seems that when we are in this fatigue states, RPE and Power should get more weighting in our triangulation

Taken as one liners without context makes you and others misunderstand what I said.

I said for me, the lower fatigued heart rate during Z2 and Z3 rides (IE, In my target zones), doesn’t matter much because the RPE is still low. Its when the RPE gets higher yet my heart rate doesn’t respond concurrently.

Disagree with the limitations of heart rate all you want, but the fact that heart rate has so many variables makes it susceptible to inaccuracy when trying to compare different sets of data. Fatigue, hydration, humidity, temperature, elevation, etc etc, heart rate will respond differently. I did not say its a worthless metric, and I wear my heart rate monitor every ride. Yes, ultimately you can look at trends. If you stay at 180 bpm at 200 watts and never improve that metric, you aren’t improving. However, I think with heart rate you need to look at very long term trends.

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