Another HR Zone Question! | 80/20 Endurance

Another HR Zone Question!

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    Andrew Brooks

    I’ve been running for about 6 years now and have achieved some pretty decent pb’s over the years from following my own training scheme (marathon sub 03:30, HM sub 01:30, 10k sub 40 mins, 5k sub 19 mins). I felt it was time for a change and read the 80/20 book and have been running an 80/20 spit for the last 6 weeks (more of a 90/10 split as I run 2 easy days, 1 hard interval day and 1 long easy run).

    I’m actually enjoying my easy runs now and arrive home feeling pretty relaxed (compared to previously!) – however I do still feel that maybe I’m taking it a little too easy on my easy runs – can I check my zone calculations?

    Age 45
    LTHR (average over the last 20 mins of the 30 minute test) 175 bpm.
    Max HR on hard intervals is 190bpm.

    This makes my easy HR zones:
    Z1 126-142
    Z2 142-158

    On my easy runs, I’ve kept my HR below 140 and have averaged around 136bpm, which equates to a pace of about 05:35 per km.

    Question – am I running too slowly for my easy runs? Having read the book I fully appreciate the theory behind keeping it easy but want to be sure I’m on the right track!

    David Warden


    Great to hear from you, and I look forward to your new PBs on the 80/20 system!

    Matt is working on a new book right now based on current research, and is adapting those finding into our 2021 Edition plans (out in December!),

    What he’s found is that you almost can’t run too slow. The slowest Zone 1 running provides 90% of the aerobic benefits of the highest Zone 2 running, but only 70% of the fatigue (these are rough numbers). If we were to rebrand, we would possible re-brand as 50/30/20 Endurance where 50 is Zone 1 and 30 is Zone 2, just to push the athlete to even more Zone 1 (today it is 40/40/20 in our plans).

    So, no, you are not going too slow on your easy runs. The real question is: are you going too slow on your hard runs? This system only works if you take advantage of those easy day to go bonkers on the hard days. That is where new fitness is gained.


    Andrew Brooks

    That’s good to hear thanks David – so keeping the easy runs really easy (in my case under 140bpm) is good even based on my zone calculations above?

    On hard days I have certainly found that I am able to really max out the intervals now – as I’m not wasting effort on my easy days!

    David Warden

    Andrew, for sure, even if the workout prescribes Zone 2, you can hang out in Zone 1. Your zones are correct based on that 175 LTHR.

    To expand on this a bit further, while the dividing line between low and moderate intensity (Zone 2 to Zone X) is empirical, the dividing line between Zone 1 and 2 is a best guess from Matt and I. Low is low, and lower appears to be better, so high Zone 1 is probably just as good as low Zone 2.

    I should clarify: Upper Zone 2 (and even Zone X) are necessary for some distances in the Specific phase of training (last 8-10 weeks before the event). You’re not going to run a Marathon in Zone 1, you’ll probably race that in upper Zone 2 to low Zone X. So, you DO want to incorporate a lot of this particular intensity as part of race -specific training. In the General phase (First 8-12 weeks) you want to focus on speed, where recovery is king from those Zone 1-2 workouts.



    Great guidance. Thanks, David!

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