Automatic Lactate Threshold Detection - Changing Training Zones?

fjt said:

I have used the automatic lactate threshold detection in the past, however I've noticed that when it detects a new threshold, it also changes my training zones slightly.

fjt said:

I've set my (run) training zones in %LTHR so in my understanding, it doesn't really make sense that it would change these.

Do you mean that:

1) it changes the percentage values of the zones while leaving the bpm values the same?

2) it changes the bpm values while leaving the percentages the same?

3) it changes both the percentages and bpm values?

- If the answer is 1), I think the explanation would be that even though you set the zones by percentage in the UI, they are actually stored as BPM under covers. In this case, if your LTHR changed, the percentage values would change, but the bpm value would stay the same. In this case, this is probably not what the user wants.

- If the answer is 2), then I would say the zones are stored as percentages under the covers, and when your LTHR changes, it's actually the BPM values that change while the percentages stay the same. Imo this is actually what most users would want (or expect).

- If the answer is 3) it would either be a bug (or possibly either 1 or 2, combined with rounding?)

For what it's worth, my zones are based on HRR% (which is a combo of max HR and resting HR). If I change my max HR manually (like from 196 to 156) and record a walk activity:

- the zone % displayed on the watch stays the same (in System > User Profile)

- the zone BPM values change to match the new max HR 

So at least in my case, it looks like the percentages stay constant, but the BPM values change, for percentage-based zones.

Every time after the watch pops up that it detected a new threshold, go to the Garmin Connect app and reset the HR zones. This bothered me too for a while, but once I asked Garmin customer support and they told me to manually reset them.

I still consider it a bug with a workaround. IMHO this should be auromatic

I can imagine there are people in both camps: Some would like the HR zones to be adjusted automatically when a new threshold is detected. Some like having known fixed zones until they have manually accepted a new threshold and are aware that zones have changed.

Considering how erratic the LTHR detection can be, I've changed camps and now I'm happy that HR zones don't change automatically...

But then just set the bpm-s. I set them based on LTHR and want them to change as I improve. If Garmin doesn't believe in their detection, that's a big issue, then they shouldn't lie to us.

I agree that most users probably expect zones based on LTHR to change if their threshold changes (meaning that the BPM values would change, based on the set percentages for each zone and the new threshold).

However, at the very least we can see that OP does *not* want their zones to "change" when their threshold is updated (whatever "change" means in this context).

I bet if Garmin flipped the behaviour tomorrow, we'd be hearing from a whole bunch of users who like it the way it is today. This has happened more than once (and there are still ongoing complaints about these changes, even years later).

e.g. Garmin now uses instant pace for workouts instead of step pace - probably to appease user complaints - but now everyone who liked step pace is mad.

Just look at this:

2019: User passionately argues in favour of instant pace for workouts: https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-945/197097/survey-for-using-instant-vs-step-pace-on-the-workout-screen

2025: "Bring back average pace range in workouts" https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-965/411412/bring-back-average-pace-range-in-workouts 

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At least this way, the user has a choice. However, it's not a very user-friendly way of "presenting" that choice. (Actually no choice is presented at all. It's only really a choice if you know that your zones should be updated, and you know how to update them.)

What would be a better compromise imo would be for Garmin to prompt the user to have LTHR zones adjusted when a new threshold is detected. Garmin could even add a "remember this choice / don't ask again" option to the prompt. (Ofc there would need to be a setting somewhere to bring the prompt back - this would ofc be slightly problematic because there will always be users who are unable to find such a setting.)

I doubt Garmin would do that since I don't think they'd be too thrilled about adding additional complexity to their UI and settings. I do agree that the status quo is not great.