Correlation between pace & hear rate zones | 80/20 Endurance

Correlation between pace & hear rate zones

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    Hi there,

    I have the following question or in other words, made the following observation but will start with some background first.
    I was mostly a runner but due to injuries, I started cycling and for most of 2020 I was focused on cycling but still ran every once in a while but very random and not structured at all. If I went out for a run it was slow, like really slow, more like a jog.
    Anyways, as I start with the 70.3 plan, I did a running threshold and running HR test. The 30 min test. I took the average pace (full 30 min) and the average HR of the last 20min of the 30min effort to calculate the zones (actually, Training Peaks did the math 🙂
    That was a few weeks ago and I slowly started to pick up running and to get used to a more structured approach.
    In recent days, I noticed that when I run lets say in the upper Zone 1 pace, I not even make it into Zone 1 HR as my HR is below the lower limit of Zone 1. Increasing my pace to Zone 2 (upper limit) I’m in the middle of HR Zone 1, no way I could bring my HR up to Zone 2 when running in pace zone 2.
    Example: upper limit pace zone 2: 8min/26s per mile. My HR would be at 135 BPM which is in the middle of HR zone 1. Only if I have to run uphill it seems to be correct/correlates.
    Is it possible that my HR vs. Pace zones drift by that much after just a few weeks back at running or in other words, did I improve that much?
    Or is it normal that the zones just don’t correlate?
    Should I retest even if I just ran my test on 12/18/2020?

    Sorry for my stupid question.


    David Warden

    Winoria, thanks for posting! Not a stupid question at all. This is a common question from athletes.

    First, you did the test exactly right and even better, captured both HR and Pace in the same test. That’s the most likely reason for there to be a delta between Pace and HR. No need to do the test again until the scheduled rest week.

    As you probably know, LTHR does not change much. What does change is speed/output (Pace/Power) for a given LTHR. Is it possible your speed changed that much in 3 weeks? not likely, but possible. I’m excited to find out when you retest in a couple more weeks! Report back here!

    But we don’t need to wait: your plan should include a ton of Zone 3 work between now and then. How does HR and Pace line up when you are in Zone 3? This is essentially just a mini threshold test. If Pace and HR are still out of alignment when you do a Zone 3 interval (at least for the latter half of the interval), then yes, you have already significantly increased fitness.

    But, let me tell you why the coupling of HR and Pace don’t matter. HR is the most unreliable and inconsistent part of training. The following external factors will change your heart rate for a given pace:

    – Temperature (as much as 1 beat per degree Fahrenheit over 70 degrees)
    – Humidity (can’t remember the values here, maybe 5 beats low vs high)
    – Time of day (4 beats higher PM than AM)
    – Stress
    – Sleep
    – Proximity to last meal (10 beats higher if less than two hours after a large meal)
    – Indoors vs outdoor (5-10 beats)

    So, unless you always run in the same temperature, humidity, time of day, hours of sleep, relative stress, proximity and size of a meal and indoors/outdoors your HR for a given pace will be very different.

    So, don’t use HR. Use Pace.



    Thanks David!
    I will stick to pace for all my training but will also report back after my next Threshold Test (I will have one in 2 weeks time from now).
    I know that there are quite some variations in HR but I don’t think that weather/temperature is causing it as the weather was quite stable (simply cold Wisconsin weather 🙂
    Anyways, I will report back shortly.



    I was going to post a heart rate related question, but I think this thread answers it. I’ve been training by power for over a year now, though I’ll make adjustments according to effort when needed. This morning’s run was supposed to be easy. My power average and pace would both be considered easy. Further, the run felt really easy the whole time. But my heart rate was higher than the level of effort would have indicated. Not sure why, but I guess there’s no real concern.


    I have another question that is similar but different but I figured it would still fit here:
    I have a LTHR of 176 BPM for running and 174 BPM for cycling. Despite using power and pace to make sure I stick to the 8020 rule, I still track my HR.
    Anyways, looking at the HR zones based on the above mentioned LTHR, my zone 1 HR for cycling is 125-141 BPM. If I ride a recovery ride in power zone 1, my HR would be well below the lower end of zone 1, averaging 110 BPM. That’s not even zone 1 and when looking at my zone distribution over the last months (in TP) I wonder if the time spent in “zone 0” would even be accounted for?
    David, what are your thoughts on this? Shouldn’t zone 1 start at 0 (zero) or let’s say 80 BPM?


    David Warden

    Winora, yes this exposes a flaw in our zone system. We really wanted to keep the zones easy to use, and so we merged the run and bike zones together. However, we all know that the max HR we can achieve is greater than the max HR we can achieve on a bike (this is actually empirical data, there are charts that show VO2max recorded by sport: cross country skiing, then running, then cycling make up the top 3). But, fortunately, we never have you perform at maxHR in any of our workouts, having you only get to Zone 5, so this is not a problem there.

    But, it is a problem on the low end of Zone 1, because a light jog compared to an easy spin will always have the light jog be a higher HR. Really, we need a set of Zones for Bike and a set of HR zones for run so that the Zone 1 of the bike is 10 beats lower.

    But here is the good news: easy is easy in the 80/20 system. While the division between low and moderate is empirical, the division between Zone 1 and 2 is a best guess, and even the floor of Zone 1 is a best guess based on years of coaching. If you are under Zone 1 and still jogging or spinning, you are just fine.

    Correct, TP won’t count any time below Zone 1. But this applies to Pace, Power or HR and you’ll see that issue in all 3 intensity types. You don’t get up to Zone 1 instantly even with power. Every time you stop it takes 3 seconds to get back up, and you lose 3 seconds of Zone 1. For sure, it is more likely to happen with HR, but it doesn’t matter if we made Zone 1 120, 100, or 80… it will not count the time it takes to get up to those zones. I would consider lowering HR to 100, but never below that as that really is not exercising anymore.

    Here’s another tip: you can override Zone 1 in TP to have it count your lower HR. Just make the bottom of Zone 1 be 100 and you’ll lose less of your “easy” in the workout analysis.



    Hello David,

    Thanks for the details on Pace vs HR zone… I think I know my answer “stick to pace” but I will ask for second opinion.

    My running plan is based on “Pace” and todays workout was Fartlek run. Workout called to run 1 min @ 07:32-08:30 min/mi Zone 4, then 2 min @ 08:40-09:19 min/mi Zone 3, etc.

    Do I have to focus on HR zones while running on “Pace”? And should I worry if my Pace calls to run Zone 2 but my HR is in Zone X or Zone 3? Btw today when I ran it was 18F outside.



    Hi David,

    I still owe you an answer on this one….
    today I ran another Threshold Test. BTW: I hate it 🙂
    Anyways, I tried to keep everything as similar as last time I ran it:
    – same shoes
    – exact same route
    – temp today: 19F, dry, overcast/sunny
    – temp last time: 33F, dry, overcast (so here we have something I cannot control – at least not yet 🙂
    – same time of the day
    – even same breakfast LMAO

    One thing was different, the HR monitor. A few weeks ago my Tickr stopped working and I bought a Polar H10 instead. Now as I think about it, this is most likely a piece of the puzzle on why my HR zone didn’t correlate with my pace zones.

    Test results from 12/18/2020:
    30min average pace: 7min 20sec = threshold pace
    20min peak Heart Rate (average): 176 BPM

    Test results from 1/28/2021:
    30min average pace: 6min 59sec = threshold pace = 21sec improvement
    20min peak Heart Rate (average): 167 BPM = 9 BPM lower (I guess that’s HR monitor related?)

    With today’s results I assume that my zones will line up – at least almost.

    David Warden

    @Nitesh In general, stick with Pace as your primary and don’t worry about HR. Particularly when you have the fartlek workouts, your HR just can’t catch up to the speed. It takes HR up to several minutes to match intensity, and by then your short interval is done. For the easier stuff, still focus on Pace when you can even when Pace and HR don’t align. To increase the odds of Pace and HR aligning, perform the test at the same time as @winoria explains above.

    Even then, HR and Pace will really only align if your next workout is in very similar conditions. If your Pace and HR test were done together in 45 degrees, but then you do a workout inside at 70 degree, your HR will react differently.

    HR is good to use for things like hills, where Pace is not accurate, or if you have a very specific/medical reason to keep HR below a certain threshold. Otherwise, your HR can be 30 beats different for the same intensity from one extreme environment to the other.

    looking forward to hearing about your next workout and how closely HR and Pace align for you.


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