Using LTHR to set training zones

After an all out outdoor MTB ride I get an email from Training Peaks telling me my LTHR has increased. Is TR and or Strava in cahoots? It’s gone from 177 to 182 in the last few months and up from 169 a few years ago. My max HR is 195. Can these numbers be trusted to be at least close? When I train outdoors, mostly endurance, it’s off HR so I wanted to make sure I was in the right ballpark.

Personally, I would probably gather data from your power meter/trainer rides rather than allow TrainingPeaks to randomly assign a number to you without any power data. Do the 20-min FTP test, or do a 2x20 threshold workout and see where you HR is at. It should get you in the ballpark.

For me personally, my average HR during the 20-min portion of the FTP test was most recently exactly what I believe my LTHR to be. HR was lower in the first half, and higher in the second half than the LTHR but the average was spot on. The following week I did 2x16 and 2x20 at threshold and my average HR for those intervals was 8-10 bpm slower than LTHR (so it’s possible my FTP is set a smidge low, or I was fatigued and my HR wasn’t responding properly).

The caveat of course is that just because your HR is say 175bpm @ FTP (held longer than 10 minutes) on one day on the trainer, does not mean it will be 175bpm @ FTP the next day outdoors. Too much variability in using HR data for specific training zones. But it can at least get you in the ballpark usually. Fatigue is a big one for me though, where I stop having the ability to even get close to HRmax, which I assume means other HR zones are equally affected.


If you’re just using HR as a secondary metric then it probably doesn’t matter all that much. If you’re training by HR zones (which I have switched to) versus training by power zones as your predominant metric then I’d be hesitant to use a race value, just like I’d be hesitant to use a race value for FTP. If wanting to use HR as your guide, probably best to do a specific LTHR test during normal training and set zones accordingly from there - way to many other factors can affect HR (and power for that matter) on race day.