Lactate Threshold HR Retest and Cross training Questions

Viewing 2 posts - 1 through 2 (of 2 total)
  • Author
  • #9888


    I read Matt’s book last year and have really been trying to implement it with fidelity.

    Last Spring I did a 20 minute TT to attempt to determine my LTHR and pace with a Garmin HR watch. My Lactate Threshold HR was registered at 191 (I know, after a year of over training — fortunately my twins were born and I haven’t done much training — that this test was invalid and that HR is much too high.
    Long story short, I retested today and came up with a LTHR of 170 and a pace of 9:41. My question is simple, not knowing anything about me, is that a reasonable LTHR to base my zones off of. I realize there is error in the watch, but this is what I have to use — I recently upgraded to a Fenix 5.

    My other question is about cross training. If I want to bike on trainer or outside on cross training days, how should the zoned training workout for that? I think I remember in the book that it said if I cross train on a bike 2-3 days / week, that the bike training should break down to 80/20 approximately. As the cross training occurs on foundation run days, should it still be in a low zone, or should I be getting my HR up into zone 3-5 for 20% of the time.

    Thanks for the help and for working to keep us injury free. (That is lifetime goal).

    David Warden


    Welcome back to training!

    Yes, a swing of 21 beats in less than a year indicates one of the two tests was wrong. LTHR is remarkably stable at threshold pace as well, further indicating one was off.

    For the time being, I would not use LTHR, but I’d use Pace instead. While HR monitors, particularly wrist-monitors, can be unreliable, GPS is usually spot on. So, use Pace for now instead to determine your zones and you can fall back to HR when you feel that the HR monitor is consistent.

    If I had to pick between the two, the 170 would be more the most likely true LTHR. An LTHR over 180 is uncommon.

    Regarding cross training, If you are following the book plan or an online plan, your cross training days replace the easy days, Zone 1 and Zone 2 runs. That way the pre-configured 80/20 ratios remain the same in your plan.

    If you are adding additional workouts on top of the written plan cross-training days, then you’ll want to manually calculate the 80/20 ratios. That’s easy: 12 minutes hard for every hour of exercise, and the rest easy.


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.