Easy runs don't seem to be easy | 80/20 Endurance

Easy runs don’t seem to be easy

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    I’m starting on my marathon plan soon. I ran a 5k time trial to reset my zones in September, ended up with a 24:55, 180 bpm for the last 20 minutes, and 8:14 min/mile as my threshold pace. When I did this test, it was 66 degrees.

    Since then, I’ve been running week 1 of the marathon plan with some cross training and a shorter “long run” at the end of the week. It has been hot. I’m a bigger guy, and it feels like I’m heavily affected by heat and humidity.

    Here’s the issue. On 10/15 I ran RF5 and it was 91 degrees. I ran 5 min Z1, then ran the 30 minutes Z2 near the slower end of my Z2 pace, then ran the 5 min at Z1 pace. 24 minutes into the run, I reached ZX heart rate and stayed there the rest of the run.

    On 10/18, I did RL1 and it was 88 degrees. Same thing, near as slow as I could run and keep in Z2 pace. 33 minutes in I hit ZX heart rate, 51 minutes in I hit Z3 and stayed there.

    These runs don’t feel easy; they feel like tempo efforts. While I know I can push myself through these runs, I absolutely feel like I’m running everything at middle intensity. I tried running RF5 by heart rate yesterday (86 degrees). I averaged 11:19 for the 30 minute Z2 effort. I started the run at the bottom of my Z2 pace, but about 11 minutes into the z2 part I had to drop into Z1 pace to maintain my heartrate, and by the end I was running over 12 minute mile pace.

    Here are my questions. Should I run my easy and long runs by heart rate and my speed work by pace? Should I abandon zones all together and run my easy runs by perceived effort? Should I just move somewhere where it’s not near 90s in October? Lol. Thanks!

    David Warden


    Your data is very helpful in answering this question.

    Everyone is affected by heat and humidity, but particularly big guys (remember, as the surface area of an object is squared, the volume is cubed! The heat that has to be dissipated in a big guy is not linear, it’s exponential).

    The truth is that your 66 degree LTHR test is not applicable to 91 degree training day. Regular viewers of this forum are rolling their eyes, “there David goes again on the risks of using HR…” But Seth, your story is a perfect example.

    My advice is to use Pace as a primary measure and HR as a distant secondary. With an 8:14 threshold pace, look at the latitude you have for Zone 1 and Zone 2. As slow as 13:43 for Zone 1 and as slow as 10:50 for Zone 2. This is really close to what you experienced in your Zone 2 run on that hot day.

    Use HR as a secondary firewall to not cross over more than 1 zone. So, it’s ok for HR to drift into Zone X if Pace is Zone 2, but don’t drift into Zone 3 HR if Pace is Zone 2, back down to Zone 1 pace to get HR down.

    Pace won’t solve a hot day completely, you still might have to slow down to high Zone 1 when performing a Zone 2, but the Pace delta on a hot day will be a fraction of the HR delta on a hot day.

    Finally, there is nothing wrong with Zone 1 when Zone 2 is called for in the workout. Here’s a small secret about 80/20: although the threshold between Zone 2, X, 3, 4 and 5 are empirically-based, the division between Zone 1 and 2 is simply based on Matt and my coaching experience. We guessed. And have even adjusted it several times over the years. We created Zone 1 to encourage athletes to slow down. My instinct tells me that the current division between Zone 1 and 2 is right, both in terms of the % of time each represents in the plan and the actual division in the zone system between Zone 1 and Zone 2, but if you end up spending 25% more time in Zone 1 than we prescribe, I think that is just fine.



    That’s exactly what I needed to know, thank you!


    David. Thank you for this tidbit of information. Very helpful.

    Use HR as a secondary firewall to not cross over more than 1 zone. So, it’s ok for HR to drift into Zone X if Pace is Zone 2, but don’t drift into Zone 3 HR if Pace is Zone 2, back down to Zone 1 pace to get HR down.

    I’ve been following 80/20 Triathlon training since last fall (after purchasing the book) and I base all my runs on pace. I’m not a heavy guy at 6’1″ 178 but I am past 55 so I always have concerns when it comes to my HR and letting it get away. Coming out of the spring when my run pace and HR seemed to jive, my heart rate would jump as well during the summer months when it got hot during a zone 2 run even though the pace wasn’t taxing. But in the back of my mind, I would heed the advice I read in the book about your views on HR and how they can vary. So I just kept trudging on. But with this piece of advice I will be able to monitor the situation better. BTW. I love running in Zone 2. It has made me more appreciative of running. Now if I can just learn to swim in Zone 2…lol But that’s another topic of discussion.



    David Warden

    Lanny, excellent comments! Thank you for contributing!


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