Auto-detected lactate threshold is horribly wrong

[sky-runner]

I’ve noticed that my stats now include lactate threshold at 145 BPM. I suspect it is a new feature introduced in the last update together with ZoneSense fields. I don’t recall seeing that before. It appeared after a run when I wore a chest strap, which I don’t normally do.

The problem is that is horribly wrong. I did a guided lactate threshold test with a Garmin watch multiple times, and it was consistently at 161-163. The one detected by Suunto is at the bottom of my zone 3, just above my aerobic threshold. I can certainly run with my HR at the upper 150s and low 160s for a long time, so my lactate threshold cannot possibly be that low.

Can anyone confirm if this is a new feature and how exactly LTHR gets calculated, and why it was detected so wrong for me?

[Brad_Olwin]

@sky-runner hmmm, mine is fairly accurate. It may be due to the differences between belt and OHR. For me none of the Suunto watches provide accurate OHR, none so I wear a chest strap most of the time.

[herlas]

@sky-runner the only new feature around this after last watch firmware is that Suunto ZoneSense post activity is now native as long as a chest strap was used (it isn’t during activity unless you enable S+ ZoneSense).

So that Anaerobic HR threshold field you’re seeing, it’s coming from ZoneSense only, and if you are not familiar with ZS you’ll have a ton of questions on this value.

[sky-runner]

@Brad_Olwin That was when wearing a HR belt. It is interesting that if I go back to that run in Suunto App now, it no longer shows Lactate Threshold (or Anaerobic Threshold) for that run, but it now shows Aerobic threshold = 135, which in my opinion is too low.

Today I’ve had another, pretty intense, run while wearing a HR belt and having ZoneSense enabled.

This time it has detected Anaerobic Threshold of 150, which up from 145 it detected last time. That is still way too low. For almost the entire run, over an hour, my HR was in 152-158 range. That felt like an Z3-Z4 effort - clearly not above the anaerobic threshold the entire time, which I wouldn’t be able to sustain for longer than a few minutes.

What is even messier is that in the Run details in Suunto App it shows Aerobic Threshold = 150, but there is no Anaerobic threshold:

But if I go into Aerobic Zones and Thresholds details it shows Measured Anaerobic Threshold = 150, but there is no Aerobic Threshold:

So clearly at least something isn’t right.

[Inge Nallsson]

@sky-runner said in Auto-detected lactate threshold is horribly wrong:

So clearly at least something isn’t right

No, it is an obvious bug somewhere, but not something I’ve encountered with my Race S and the Android version of the Suunto app. Here is the latest aerobic number:

And the whole week has been spot on, reflecting coming back after a small injury, with dropping aerobic conditioning and a few days of unbearable temperatures followed by rainy ones. Trying to do ‘easy’ trail runs of around one hour (except the last one which was a village run of 32 minutes):

“Measured” “Aerobic threshold”
140 bpm 20.1C–20.9C ZS Green 67% Yellow 33%
146 bpm 26.4C–28.6C ZS Green 74% Yellow 26%
144 bpm 16.1C–16.0C ZS Green 81% Yellow 19%
141 bpm 14.9C–14.7C ZS Green 86% Yellow 14%

By the way, at least with the Race S there is no need to activate the S+ ZoneSense app in the watch. Everything is native as long as a HR strap is in use. The app only gives a nice graphical view of the effort level.