High HR when hitting correct power zones? | 80/20 Endurance

High HR when hitting correct power zones?

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    Hi All,

    I’ve started a full iron plan. Only into week 2 so far. I have a query around Power and HR. I guess I want to make sure I’m doing things right before pushing on with the plan.

    I completed CCI13 today. Using power, on zwift. I know my ftp is correct as I tested before starting the plan. So I’ve produced the power required all through using a wahoo kickr. I’ve spent an hour at z2 power, but an hour at z5 HR?

    If I was training off heart rate it would be a completely different workout and much easier?

    I would screenshot the zones off TP but cant see a way to do so?

    Hopefully what I’m asking makes sense.

    David Warden


    Welcome to 80/20 training!

    A disparity between HR and Power/Pace is a common experience. Two ways to address this:

    1- HR and Power zones might, but only if you tested them at the same time. How did you identify your LTHR? It would be best to use the HR data (peak 15 minutes BMP of the exact same test where you got your FTP). I’m guessing that your LTHR was identified in some other method other than the 20-minute protocol we recommend in our documentation.

    2- Even if you test FTP and LTHR in the same test, the nature of HR is that it will change for a given power output based on the environment. A give n power output of 250 watts can have a swing of 20 BMP one day to another based on temperature, time of day, stress, sleep, humidity, indoor or outdoor training even when you last ate.

    So, if you have Power, don’t even use HR. Just use Power.



    Thanks David. That makes sense. I’ll just stick with power.


    The same thing used to annoy/perplex me when I was was starting to use power, but was very much used to using HR. Even though of course they all lined up when I tested them on a lovely flat as a pancake seafront quick course, as soon as I ran on my hilly (for here) easy run route they quickly separated. I don’t really look at HR now, just power zones – with an HR check occasionally if I’ve found the workout to be tougher than expected to see if it ties up etc. However, since I’ve ‘divorced’ HR and stopped looking at HR religiously, life has been easier, my watch beeps less at me, so it’s all good 🙂


    I wouldn’t worry too much about heart rate drifting higher. There are times when a higher heart rate can be indicative of other factors that might necessitate backing off. For example, fatigue from a previous hard workout, dehydration, etc. But in these cases, I’ve found that it’s just as effective to use your sense of perceived effort to recalibrate as needed. When this happens, I’ll adjust my effort to what feels right and then try to keep power at this level.

    David Warden

    My name is David Warden and I approve this message.


    What about the flip side to this? I just finished my second block of the advanced IM plan, and I have my HR oftentimes staying in mid to upper Z1, even though my pace/power is in high Z2. I have also noticed even though I can feel my run and bike endurance fitness increase, I make only very small improvements in my 20 min FTP/LTRP tests. My guess is because IM training is very different than focused 5k run or bike TT training, but I just don’t want to be missing my key intensity levels. i.e., my hrTSS vs. my bikeTSS or rTSS in Trainingpeaks are sometimes 20+ points different, with hrTSS always lower. Any adivce?

    David Warden


    It’s certainly more common for HR zones to exceed Pace or Power zones due to cardiac drift. However, the opposite is not uncommon. Some reasons for this could include:

    – Of course, our default position that unless you identify HR, Pace and Power in the same 20-minutes test, they will not likely align.
    – Indoor HR is 5-10 beats lower than outdoor, but power stays about the same. So, if you tested outside but then train inside, HR zones will be lower than corresponding Pace or Power.
    – Fatigue will reduce HR, but, it usually means that your Pace and Power are also just as low, so this is less likely.
    – It’s just the way your HR works. Some athletes have much less drift and delta than others, whether through fitness or genetics.

    To address your other comments, we’d expect both your general endurance and your raw thresholds to improve with 80/20. However, here are some reasons we’d see very small or no gains:

    – As you point out, the final 8-12 weeks of HM, Marathon, 70.3 and IM plans are designed for specificity, which means endurance not speed. I would not expect to see much gain in threshold output over the last half of any given training plan.
    – More experienced athletes will of course see smaller and smaller gains.

    TSS and rTSS will almost always be very different from hrTSS. Why? Because Pace and Power changes are instant, but HR lags behind the intensity. For example, when you go from Zone 1 to Zone 5, you Pace and Power goes instantly (more or less) from Zone 1 to Zone 5. With HR, you must first pass through Zone 1, then 2, then X, then 3, then Y then 4 then you reach Zone 5 just as the interval ends. TP doesn’t accomodate for this in their calculations, so while you spent 60 seconds in Zone 5 by Power and Pace, you spent 10 seconds by HR.

    This is a hyperbolic example, but it will result in hrTSS always being off from Pace and Power.

    Finally, there is a bug in TP for hrTSS. See https://www.8020endurance.com/your-performance-management-chart-is-lying-to-you/ for details on that bug.



    Coach D,

    I understand the cardiac lag part and I would never compare my hrTSS and my rTSS for an anaerobic or interval workout for exactly that reason. But I would expect my hRTSS and rTSS/bTSS be somewhat comparable during steady state efforts. But I consistently find my hrTSS to be lower than my rTSS. fpr example during my last RF12 last Saturday, I tried to run at upper Z2 so my rTSS ended up being 119 (compared to 109 planned), yet my hrTSS for the same workout was only 79. So I thought to myself “great looks like you’re outperforming your zones so next test should be a great improvement” yet during my 20-min test yesterday I barely added .1 miles to my distance (RTHP from 6:47 to 6:42, while LTHR stayed at 183 based on your updated 15-min peak protocol). I just want to make sure I stay in the right training zone and to make sure I don’t over or undertrain. Is there even a risk to undertrain during long runs/rides? Should I focus more on my hr zones or my pace zones during those long steady state efforts? Thanks!


    David Warden


    For sure, the delta between HR and Pace/Power should be less for a steady-state run, but the problem described still exists. It will take 5 minutes for HR to reach upper Zone 2, so for nearly 10% of your easy 1-hour run your HR is still catching up, while Pace or Power are in upper Zone 2 immediately.

    Regarding the difference between TSS for Pace, Power and HR, this is just the nature of how TP works, coupled with a bug in hrTSS (documented in my PMC article referend above). To illustrate this, I’ve loaded 3 RF12 workouts by Pace, Power and HR and TP is estimating 87, 97, and 109 for the exact same workout. This predicted TSS issue will carry into the actual TSS. See attached.


    Ultimately, it really does not matter if TSS lines up. Imagine you access 3 scales at home, work, and the gym. One tells you you weigh 160, the other 165, the other 170. Which is correct? One of them is, but as long as you use just one scale to monitor progress, it doesn’t matter which one is accurate, it matters which one is consistent. The same issue exists with power meters. Run a Stages, Vector and a Powertap on the same bike and you’ll get 3 completely different power numbers. Which one is right? Doesn’t matter. Just pick one device and use it.

    Therefore, pick one TSS: HR Pace or Power and stick with it. Don’t try and make them all fit together.



    Sounds good, thank you! I will stick with rTSS and ignore the hrTSS calc in TP going forward.

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