20-minute test confusion | 80/20 Endurance

20-minute test confusion

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    Hi! I’m new to 80/20 and David kindly gave me a couple pointers when I bought the plan. I even bought a Coros watch after hearing from him. 🙂

    I did the 20-min speed test today and I’m pretty confused… I ran for 20 min. at what I felt I could hold (about 7 min/mi consistently) and felt tired after. According to the Coros, my average HR for those 20 min was 136.

    I’ve done two runs with this new Coros prior to today. The first was a hilly 6 miles at 9:15/mi, average HR said 162. But it didn’t feel hard at all.

    The other was an easy run, 3 mi at 9:38/mi, definitely felt easy. Average HR for that says 138, which is HIGHER THAN MY 20-MINUTE TEST?!?!

    As you can see, I have no idea what my true LTHR is supposed to be. My 50k training plan starts this Tuesday so I’m kinda in a rush to get this figured out. Any advice so appreciated!


    Ooh, I found one more run I did with this watch! Definitely easy trail run, 3.5 mi @ 9:47, average HR 150.

    It’s driving me nuts that I’ve had three “normal” runs with average HR 138-162, and my 20-min speed test average HR is 136… I have wasted WAY too much time trying to figure out what’s going on haha!


    I never trust wrist based HR but only use chest straps (highly recommend polar’s H10).
    But doesn’t Coros have a build in running power meter anyways?

    David Warden

    @winoria, love the new profile pic.

    Angela, yes, this would be confusing! Two things I think are going on here:

    – If you are using wrist-based HR, this is notoriously unreliable. Use a chest strap when you can.

    – If you have Power built into the Coros, use that instead of HR or at least use Pace. Pace and Power are going to be mush more reliable than HR, even with a chest strap. HR is not a consistent measure (apologies here to our forums veterans who have heard this over and over from me…). HR can be 25 beats off for the same pace based on temperature, humidity, time of day, sleep, stress, AM or PM and indoor or outdoor run. Remember, you can always switch to Pace or Power versions of your plan for free with 80/20.

    If you really want to use HR, we can pull this off. You’ll want to make sure your wrist strap is nice and tight, or use a chest strap. You’ll also need to recognize that higher temperatures will elevate HR, indoors will lower HR, AM will lower HR va PM (about 4 beats). You’ll eventually understand what your “environmental” HR really is and adjust each time.

    For now, since you’re ready to get training, consider using our Pace calculator using a recent running event at https://www.8020endurance.com/8020-zone-calculator/ That will al least get you going until you can get your HR sorted. Or, if you captured Pace on your test run, you can use that at the calculator as well to get your Pace zones for now.



    Oh gosh, I promise I read the plan and the linked resources, but I guess I misunderstood it– thanks for your patience! (I somehow still thought HR was the goal, but power sounds way better.)

    If I highlight just the 20-min section, my Coros says average Power = 270 (max 312). Sound realistic?

    I’ll put that into the calculator for now, and I submitted the form to switch to power. This is a relief, thanks to you both very much!


    @david: quite cold here right now. Ran around noon as it was supposed to be the warmest time of the day: 9F brrrr

    David Warden

    Angela, 270 watts is a running threshold consistent with a female runner. I think you can use that value with confidence.

    Winoria, we admire your discipline! Keep it up!

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