Half-marathon Z2 is actually Zone X | 80/20 Endurance

Half-marathon Z2 is actually Zone X

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  • #14430

    I’m doing the half-marathon, Level 2, heart-rate based, and I’m puzzled about how much of the HR work on Zone 2 days pushes you into Zone X. Is that by design, or am I doing something wrong? I’m about midway through, and today’s ER12 Endurance run calls for HR 131-146. I have an AeT around 138, so anything above that puts me out of Z2.

    I don’t want to overthink this, or make the rules too hard and fast, but I want to make sure I’m not misunderstanding the program.

    • This topic was modified 11 months ago by timbenz.
    David Warden

    Tim, thanks for using our plans and posting on the forums. A few questions to narrow this down:

    – Since you can throttle your pace when using HR, why not just slow down to keep your HR in Zone 2?
    – Based on a Zone 2 of 131-146, your LTHR is 162. Does that sound right?
    – How and when did you last establish your LTHR?
    – AeT is not used in the 80/20 system. If you under 146 on a Zone 2 run, you are doing it right. Our “easy” is anything below Zone X.

    Finally, consider switching from HR to Pace. Pace is a more reliable method for measuring intensity in most circumstances. You can switch you plan intensity type for free at https://www.8020endurance.com/contact/



    Thanks David. To answer your questions:
    – Yup, I can obviously run at a slower pace, but I wanted to make sure whether the point of the plan was to have me run some of the time in Zone X when it says Zone 2-X.
    – My Zone 2 is more like 128-138, with 138 my AeT, hence my puzzlement at the 131-146 suggestion from the plan, which includes a chunk of Zone X
    – Last tested the LTHR three months ago with a blood test, and then reconfirmed in August with an LT test on my Garmin. I know, not scientific, but still.
    – Finally, I decided to use heart-rate because I’m running on fairly hilly terrain, and training based on pace causes me all sorts of over/under issues.

    Thanks again.

    • This reply was modified 11 months ago by timbenz.
    • This reply was modified 11 months ago by timbenz.

    ER12 doesn’t call for Zone X

    Have you made sure the zones on TP and your watch all match ?


    Here is what the plan said for ER12, which includes Zone X targets:

    Workout Details

    5 min @ 117-131 bpm
    Zone 1-Zone 2

    1:45:00 @ 131-146 bpm
    Zone 2-Zone X

    Wrt syncing zones, they do, but there seems some confusion about this, with 8020 explaining on the site how to do it (within Garmin limits), but that it is no longer necessary if you are using an electronic plan or the 8020 Garmin app.

    David Warden

    Lot’s going on here, short answers first:

    – That workout does not include Zone X, it is just Zone 2. The Zone X reference is a glitch in TP, use the values of 131-146bmp, which is just Zone 2. More details below.
    – Your Zone is is not “more like 128-138.” Your Zone 2 is 131-146 in the 80/20 system, (assuming your LTHR is 162). You can’t mix and match zone systems, when you adopt the 80/20 system, you abandon all other systems. It’s not that the other systems are bad, you just can’t combine them. It’s like choosing the metric system or Imperial system to build a rocket to Mars. Both are equally accurate, but if you mix them together, the rocket will crash.
    – Lab LTHR tests are good, they are more precise than field tests, but there are two problems with using lab tests: 1) lab tests are only done inside on a treadmill. Inside vs. outside HR is 5-10 beats different. Your indoor LTHR is 162, but your outdoor is at least 167, maybe 172. If you train 100% inside, great! I suspect you don’t. 2) LTHR changes. 3 months is an eternity in training. Both of these issues mean field testing outside will always be more accurate than LTHR. Lab test are precise, field tests are accurate. Use our 20-minute testing protocol instead, and test every rest week per our documentation.
    – Garmin LTHR estimates are not accurate. Field tests are accurate.

    – I’m confident a review of the documents and Q&A of Getting Started with 80/20 Training, Intensity Guidelines for Running, and Understanding Your TrainingPeaks Structured Workout Plan as many of the these issues discussed here are covered there.

    The Workout Description will occasionally include two zones, but the values (131-146) are all that matter, not the description. 146 is both the top end of Zone 2 and the bottom end of Zone 3…by only 1bpm. So, you are not meant to go into Zone X on that workout, it’s just a glitch in TP. Your maximum HR for that segment is 146, which is the top of Zone 2. See Understanding Your TrainingPeaks Structured Workout Plan but I’ve included the relevant section here for your convenience.

    The short answer is: use the values in the workout description.

    Q: Why does the Workout Details section sometimes list more than one zone, such as “Zone 4 – Zone 5”?

    A: In order to avoid gaps between zones, TrainingPeaks requires the 80/20 zones to overlap. Therefore, occasionally the custom intensity values presented by TrainingPeaks in the Workout Details will span more than one zone. Note that the zone range values presented in the Workout Details are still precise, and you should use those range values as your primary target. However, if you are presented with more than one zone in the Workout Details, use the zones listed in the Workout Description or the guidelines below. Again, you can ignore the zones and focus on the actual intensity range values provided, which are accurate if you have followed the instructions in this document.

    If presented with a span of two zones (i.e. Zone 2 – Zone X) the lower of the two zones presented is the correct zone (in this example, Zone 2)
    If presented with a span of three zones (i.e. Zone 1 – Zone X) the middle of the range of zones presented is the correct zone (in this example, Zone 2)



    Thanks David. Apologies for being so thick, but I was genuinely confused and clearly missed a few things on the site guides.


    1) I take your point wrt 8020 being different from other zone models, which had confused me. I assumed the top of 8020 Zone 2 was AeT, as in other zone models. Now I understand.
    2) I will redo the LT test, as you suggest. It’s overdue.

    Thanks again.

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