Subject: Feedback on Zone Sense accuracy: Short intervals and Zone 2 threshold shifts
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@Dieter1960 doesn’t the documentation state that ZonseSense cannot detect short intervals at all?
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@Dieter1960 If you read the documents and watch the videos, you will gain answers to your questions. ZS is ineffective on short intervals, I personally would not use on any interval less than 20 min or so. There is a lag of 1 to 2 min for ZS to implement changes.
For AT I have tested ZS prior to the public release and since then (for over 1 year) and for me I get both AT and LT accurately but only if I spend significant time in HR zones at or above AT and LT. ZS is primarily intended for live values and its ability to detect zones will depend on how recovered you are. On days I am well recovered for example, after a recovery week, I get AT values near my lab measured values. On days where I am in a training block my AT from ZS can be 20bpm lower than my measured values.
So:- Don’t use 1 or 2 exercises to calculate either AT or LT, a lot are required for me.
- ZS is an excellent measure of RPE for me and for some others on the forum.
In my opinion you are asking for ZS to do something it is not intended to do. I doubt the AI analysis is as good as the algorithms (patented) that ZS uses from Monte Cardio (not sure that is correct.)
You can search the forum for a lot of discussion on ZS.
Vector/T6c/Ambit 3 Peak/S5 Copper/S3/S7 Ti/S9 baro Ti/S9P Ti/S9PP Ti/Vertical Ti/Race Ti/RaceS/Ocean/Wing/Race2Ti
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Thanks for sharing such a detailed feedback. Your experience as a long-term tester brings a lot of clarity to how Zone Sense (ZS) actually behaves in the field.
A few points you mentioned really resonate:
• The Lag & Stability: You’re spot on about the 1-2 min delay. It confirms that ZS is a physiological tracker rather than a real-time reactive tool like pace or power. It’s clearly not built for short bursts.
• Fatigue vs. Lab Values: Your observation about the AT dropping by 20bpm during heavy training blocks is a perfect example of what ZS is meant for. It tracks daily physiological capacity rather than theoretical fitness. It’s more of a ‘form’ gauge than a fixed calibration.
• Consistency: I agree that judging ZS on a single session is a mistake. It takes time and a significant volume of data in the higher zones to see the patterns emerge.
Using it as a dynamic RPE guide instead of a rigid zone system seems to be the most effective way to use the technology. Thanks for the heads-up on the algorithm origins as well ! -
Monitara
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@Dieter1960 to expand on this, there is a Lecture Series of YouTube videos done by Suunto. There is lengthy talk about the Training model of Suunto and ZoneSense even with a guy from Moni Cardi (if I got the name right), that highlights the dos and don’ts…
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@Dieter1960 said in Subject: Feedback on Zone Sense accuracy: Short intervals and Zone 2 threshold shifts:
Underestimation of the First Threshold (Aerobic)
During steady Zone 2 sessions (based on Garmin LTHR outdoor baselines), Zone Sense consistently marks me as being above the first threshold (moving into “Yellow/Red” zones in the app).This is my experience as well. I stopped caring about ZoneSense altogether because it consistently detects both LT1 and LT2 way too low. It sometimes detects LT2 at a HR that is even below my aerobic (LT1) threshold. Perhaps I use it not the way I am supposed to, but if it is too difficult to use correctly, why should I bother?
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@sky-runner I agree
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I see a very big difference in ZS feedback based on the sport. If I do XC skiing, it says my LT1 is 158 bpm. If I do treadmill running, it says my LT1 is 128 bpm. My breathing pattern tells me my LT1 is around 142 bpm. ZS is basically ± 15 bpm for me. It’s not enough for consistent training and is still not a replacement for a lactate meter. I understand the point about day to day variability, but going from 158 bpm to 128 bpm next day seems unrealistic. I wasn’t collapsing or anything, just the usual microcycle.
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I totally agree. While daily variability is a physiological reality—especially with factors like fatigue or heat—a 30 bpm swing is simply unrealistic.
Zone Sense should use a rolling average or a baseline from your previous sessions. It shouldn’t ‘start from scratch’ every time you switch sports. Even if the internal load differs between XC skiing and running, the algorithm needs a memory of your history to stay consistent. Without that anchor, the data becomes too volatile to trust for daily training. -
@Brad_Olwin said in Subject: Feedback on Zone Sense accuracy: Short intervals and Zone 2 threshold shifts:
ZS is primarily intended for live values and its ability to detect zones will depend on how recovered you are
In that case ZS shouldn’t be used to detect zones but that is exactly what Suunto does. It remembers the last detected thresholds and tells me about them later. For example, a few seconds ago I looked at my watch and it showed me that my Lactate Threshold is 145, which is nonsense because that is just one or two beats above of where my AT is based on multiple years of observation. I can still mostly breathe through the nose at that effort.
