Can't keep heart rate in Z2 | 80/20 Endurance

Can’t keep heart rate in Z2

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    Hi, my LTHR is 156 – based on the average HR during the last 20 mins of a 30 min run where I was doing 5.26 min/km pace. This means for my Zone 2 I need to stay under 140 HR which I am finding impossible. Even running as slow as I can (8.00 min/km) my heart rate creeps into the 150s. I have tested this with both my Garmin wrist and a chest strap HRM. This is my third week doing 80/20. Is this normal and should I just keep going at this pace hoping my HR will eventually drop or do I try to go even slower which would basically be walking.

    David Warden


    It looks like you preformed the thresholds test exactly right, assuming that 30-minutes was the maximum pace you could maintain for that period.

    Your situation demonstrates the disadvantages of using HR as a primary measure of intensity. It is unusual for your LTHR to be 156 AND for you to easily reach 96% of your LTHR when running easy. But, it’s not unheard of, that’s just the way your heart responds to exercise.

    It’s possible your HR will “settle in” but that is also uncommon. There is a certain set of athletes where HR stays within a 15 beats range during exercise regardless of intensity. It’s not bad or good, it’s just the way your cardiovascular system works.

    It’s also possible that on that particular day your HR was suppressed for a variety of possible reasons, and that the next threshold test you perform will have you at 165

    The solution for you is to take that same 30-minute test and find your average pace over that 30 minutes, and use Pace instead of HR as your primary measure of intensity at least for the next couple of months. Remember you can always switch intensity types for free at



    Thanks David. I am due for another test so will give that a go.



    I did my first training session yesterday with a chest strap monitor. It’s the Polar H9 I think.

    I noticed that I was able to run faster than normal and stay in my Zone 2 with ease.

    Typical runs for me are around 12:20 – 12:30 in Zone 2 with the Garmin watch monitor. Yesterday on my long run, I was down in the 11:30’s and easily staying in Zone 2.

    Have you seen a major difference in readings between the 2? I am assuming that the chest strap monitor is the more accurate tool for measure?


    Hi thomassayle

    I’ve only had the chest strap for a week so might be too soon to tell, but so far I haven’t seen any difference. I bought it as I thought the wrist HRM must not be accurate as it was reading so high. But unfortunately I am so far getting the same results with the chest strap.

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