LTHR, Reconciling HR data, Training in lower bound of Zone 3,4

Viewing 4 posts - 1 through 4 (of 4 total)
  • Author
  • #9643

    In the last few days I’ve spent a good chunk of my time reading through questions from runners alike and answers from Dave and Matt — it’s been super helpful to gain even more understanding of 80/20. Let me first start by saying I hope the following question serves the broader forum and not just myself.

    2 weeks ago Dave helped me pinpoint my LTHR and we came away with 6:20 pace based on a 5k TT on the track that I posted mid November (FTR, there is a calc that computes this info for you on the website but I was still unsure of my findings so much so that I needed someone to confirm it for me) I ran 19:13 but there was 95% humidity and the temp was 65s — FWIW I run terribly in warm conditions! To that end, my HR was 193-194 from lap 5-12 and felt I was maxed after 2mi.

    A threshold pace of 6:20 per mile seemed rather *ambitious* and I had a tough time accepting it, truthfully. But it gave me just enough confidence to head out on the track to see if I could actually will myself to 20 laps at that blistering pace or close to it. So two weeks later I set out to see about it…

    I had the perfect conditions at 7pm, 48 degrees w/ zero wind and normal humidity. 6:20 pace would be 94 secs per lap. Struggled to find my rhythm early on but settled in on 96 seconds. The two sec lap differential felt material — at least mentally. And that if I were to try it , I wouldn’t be able to sustain it or worse blow up before 5 miles, which would defeat the purpose of this workout. Ended up avg’ing 96 sec for 20 laps, good enough for 32:21 ~ 6:28 pace. Did it hurt? Yes. Did it feel like I was all out? I don’t know how to answer this. On the one hand, I felt spent. But when compared to the 5k TT, it didn’t hurt nearly as bad as that. Judging by the HR data, I was in the 190s during the 5k for the last two miles. On this recent effort, i maintained a HR avg of 183 for the last 20min.

    My questions are as follows:

    Should I update my threshold pace to 6:28 or keep it at 6:20? That test was on Dec 4th. How often should I retest? Apologies if i missed this in the book.

    When a workout calls for some speed play in zone 3 or zone 4, I find that there is a large gap between either zone in my case, Zone 3 is 6:28-6:57 and Zone 4 is 5:37 – 6:20. There is less focus on hitting exact paces. Does this imply that you get the same fitness benefit no matter where you are at on the Zone 3 or 4 spectrum? Naturally, i gravitate to the faster end assuming it’s doing more for me.

    Lastly, my virtual 10k (first ever 10k) is on Jan 16th. As I mentioned, I would like to use your program next. Do I need to take any extended breaks before jumping into another 12 week training block? FWIW, I feel healthy, fresh, and good overall. All that to say, I’m ready to jump right in to do 80/20 training program. Currently avg’ing 45-50 mi per week, should I do Level II or III?


    Dave, meant to link the the Threshold run to the post above. Here it is. It’s 20 laps though it shows 4.97 miles (GPS and track inaccuracy). I was able to split every lap on the watch so that level of detail is there, too.

    David Warden


    Thanks for posting. These are really helpful questions and experiences and I appreciate you sharing for the rest of the community to benefit.

    Use the 6:28 as your new threshold. I’d give our calculator a B+ grade at estimating your threshold (sometimes we get an A, sometimes it’s a C-, it varies by athlete), but your 30-minute TT is precise and our calculator is just an estimate.

    Your second question is a great discussion. Let me break it down into a few parts:

    – One of the benefits of using a range instead of a target is it can adapt to your level of fatigue. Fatigue is not completely predictable. You could have two athletes perform the exact same workouts, duration and intensity and on day 21 they could be experiencing very different levels of fatigue. If you are feeling a bit tired, then the low end of Zone 3 is great. If you are feeling strong, target the high end.

    – What really matters is consistency within the zone for a given workout. In a given workout, it’s better to perform the 4 intervals at 75% penetration of Zone 4 than 4 intervals all over in Zone 4. In this regard, you actually can use a specific target within the zone based on your fitness level and level of fatigue.

    – The benefits of the upper level of the zone are going to provide you better results than the lower end. When you can, use the higher end, but again only if you can maintain that level for all intervals in that session.

    Take at least a week off before you jump back into the 10K plan. “Off” just means no real plan, go as you feel, but no more than 4 hours for the week.

    The decision on which level is based on how much time you can commit to train. Of course, you’ll have better performance with the Level 3 plan, but it’s demanding. Remember, you can always switch level for free so you can’t choose wrong. If a level is too hard or too easy we can make that change for you.



    David, again thank you! This information is super helpful as I plan ahead in the New Year. Don’t be so hard on the calculator lol. After all, the threshold test is the real measure that you and Matt encourage everyone to take. With someone pushing me however, I’m 95% confident I could have mustered 6:21 – 6:25 pace. So technically you were closer to 98% accurate than the “purported” 95% lol.

    On a more serious note, if anyone is reading this, it sucks but it’s absolutely necessary that you take the darn threshold test and not replace it with something else.

    Big goals for 2021! Can’t wait to begin level 3 10k next and prove to my 38 year-old self as well as a host of old high school running buddies that I will thrash them with 80% of my runs in Zone 2!

    Merry Christmas to all!

Viewing 4 posts - 1 through 4 (of 4 total)
  • You must be logged in to reply to this topic.
Posted in


You must be logged in to create new topics and to reply to topics.