Thinking my Lactate Threshold HR is Wrong…

Viewing 2 posts - 1 through 2 (of 2 total)
  • Author
  • #16575


    After a long time off (chronic injuries) from running I started to run again at low heart rate/ low intensity after reading Matt’s recent book (“80/20 Running”) and having a revelation about why I was getting chronically injured. I’m probably not alone there I’m sure.

    Four months in and I’m doing great injury wise and feeling strong! Now for my confession: I realized a few weeks ago that I’ve been running my zones based off of my Garmin heart rate zones which of course are based on a guess at my maximum heart rate and which of course also don’t not line up with the zones Matt uses in his 80/20 book which are based off your Lactate Threshold heart rate. Yes I see now this was probably a mistake. Once I realized this, I felt dumb and decided I would do the test he outlines where you run a 30 minute time trial (p.111 in my book) and take the average heart rate from the last 10 minutes. For me, it was extremely difficult of course but I got a result of 171. I went ahead and figured out my heart rate zones according to his 5-Zone system and have been running with these zones this week.

    My question is, how difficult are the upper zones supposed to be? I’m finding that running at Zone 3 is extremely difficult and basically feels like a speed workout. It is only sustainable for maybe five to ten minutes if I’m feeling really strong that day and I can only stay in the bottom 1/3 of the zone. Zones 4 and 5 are so difficult as to be almost impossible although thankfully they are rare in my plan at this point. Is this “normal”? I feel like maybe I did the test wrong? Also, I always run with a chest strap on so I believe the numbers I’m getting are accurate. I’d really love some help here as I’m really confused and thinking about adjusting my heart rate to get a different result. Thanks!

    David Warden


    Thanks for posting on our forums. There is certainty a bit of an immediate mystery here:

    You can run at the same maximum output for 30 minutes (top of Zone 3) on Day 1, but can’t run for 3×6 minute intervals at the exact same intensity on Day 4.

    I suspect it’s just a matter of adjusting for cardiac lag. Your Zone 3 target is 162 to 171bpm. It’s going to take a few minutes for HR to catch up with your intensity. If you are trying to get to 165 in the first minutes of your Zone 3 interval, you’re going too fast. For Zone 4 and 5, we your HR will never catch up (as we discuss in our document Getting Started with 80/20 Training).

    For some athletes, it can take 5+ minutes for HR to catch up, even on an interval, which makes HR training impractical for many athletes.

    This is why Pace is superior to HR for training. It’s instant and has no lag. I recommend you take that same 30-minutes test, grab your average Pace to determine your threshold Pace, use Pace zones and drop HR altogether.

    It’s not a matter of the wrong LTHR, that 30-minute test is the gold standard and if you can run for 30 minutes at the top of Zone 3, you can run Zone 3 intervals for much shorter periods. It’s probably cardiac lag.


Viewing 2 posts - 1 through 2 (of 2 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.