Suunto ZoneSense
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I only ever look at zone sense in the app after a workout, I have found it wildly inaccurate at times and others fairly accurate. For me the gold standard is RPE followed by HR however even HR can be misleading as I’m often training fatigued and when doing an hour long effort at near threshold in terms of RPE when fatigued my HR might only be in high zone 3. When fresh HR seems to align better with RPE. Zone sense has often shown nearly all green with a few tiny spurts into yellow when I’m at 9-9.5 RPE doing a threshold effort up a vertical kilometre!!!
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@Doodoo-Runner said in Suunto ZoneSense:
@sky-runner this reviewer did lab tests along with ZoneSense . Among his group was DC Rainmaker. The findings suggest Zonesense is not to be trusted.
curious to know why, with the same HR source, the SV and SR results differ.
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This reviewer did a lab test along with ZoneSense and came to the conclusion that it’s very good:
https://www.youtube.com/watch?v=G9Sr0-Ig_oQ
Written form: https://www.nakan.ch/wp/2025/09/17/tout-savoir-sur-zonesense-de-suunto/#Conclusion_sur_lalgorithme_ZoneSense_de_Suunto
Just to show that in today’s world of influencers it doesn’t take long to find someone who claims the opposite.
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@Brad_Olwin I agree - it’s the real time feedback, that is most valuable and for me too it really corresponds on how I feel. I used to train a lot by HR Zones and sometimes it worked great but often I felt they were too low to or too high compared to my set zones (having had a tested LTH).
With Zonesense this feels much more ‚realistic‘ and actually Zonesense for me is (besides others) one of the features why I would never use another brand. -
@Brad_Olwin I don’t really get what you want to convince me of. I am just stating scientific facts and want to point out that the accuracy of ZoneSense is just based on anecdotal information like yours and that the scientific data rather hint to a too high inaccuracy to recommend it for training control on a population level. Therefore, users with strange data should not be unsettled that they do something wrong in their training.
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Is it possible to turn Zonesense off in the app (iOS). I do not use it. Unfortunately it set default in the graph.
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@MarkusG big problem of our modern society where everyone can just spread unverified and anecdotal information! Better rely on verified data from independent researchers and experts. But apparently there is too much money to make with just claiming that you have developed something special. Garmin is the worst example with their “body battery”, “heat/height acclimation”, “Real-Time stamina”, “endurance score”, “training readiness”, “running tolerance”, “race predictor”. Nothing of that has ever been scientifically validated that it actually works and every good coach and athlete can do more accurate race predictions
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Is still something happening with Zonesense? I don’t think it is mature enough to stop development. Or maybe its in a dead end?
Apart from @brad_olwin there are not many reports about the feature working.
For myself I am using it to verify my HR and Powerzones from time to time. Just comparing Zonesense TSS with TSS(HR) and TSS(p). But real time its still absolutely random
(New belt, new battery, moistened with water and gel, 10min slow intro, tight fit and sweating like in hell)
Race S
Vertical Titanium Solar
Ambit3 Vertical
Eon Core -
Is still something happening with Zonesense? I don’t think it is mature enough to stop development. Or maybe its in a dead end?
Apart from @brad_olwin there are not many reports about the feature working.
For myself I am using it to verify my HR and Powerzones from time to time. Just comparing Zonesense TSS with TSS(HR) and TSS(p). But real time its still absolutely random
(New belt, new battery, moistened with water and gel, 10min slow intro, tight fit and sweating like in hell)I’ve found ZoneSense to be interesting but problematic. First, the ten minute calibration I’ve found needs to be managed carefully. You can’t go too hard, but nor can you go too easy, or else you’ll get problematic results. I normally consider my AeT / LT1 to be 144bpm, but yesterday doing a Wahoo SYSTM structured indoor bike workout ZoneSense thought it was 122bpm, as the workout featured a very light warmup. With a proper warmup it’ll give me my expected result, are very close to it (e.g. 140-148bpm range).
Because it’s a lagging indicator, interval sessions sometimes don’t even register. A track workout of 400m sprints, with 400m walks may or may not register; 100m sprints almost certainly will not.
For an indoor rowing workout, where sessions might only be 10-20m with short intervals, the calibration time takes most of the session, the intervals are too short, and I can’t really glance at my watch during the session so it’s useless for that modality live. If I do a longer 20-30m session, starting steady-state for the first 6-8m at 120w, then increase to my rowing FTP of 160w for the final couple minutes of calibration, that tends to work decently to get it right but I still can only make note of the data after session and not during.
I find it best in running as a “secondary indicator” after normal HR when returning to a longer, slower effort after a harder push. If I do 1km at a threshold effort, then return to a lighter effort, I’ll first notice my HR dropping down to zone 2, then about a minute later ZoneSense will return “green,” and sometime (typically when weather is hot), I need to dial down HR a bit more, so rather than settling in at say 140bpm I’ll go a little slower and get to 136bpm and then ZoneSense will be happy.
At this point though a lot of this I’ve internalized as RPE so looking at ZoneSense “live” during session I don’t typically need. Now, if ZoneSense could “remember” say my last week/month of data, and use that as “temporary, provisional” info while during the calibration, then that might be helpful but I suspect that’s against the philosophy of what it’s doing.
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@raven This is also my experience. But today I watched a spanish YouTube video analyzing Zonesense. They say if you correctly calibrate Zonesense, then it also works during runs. Slower and just three zones, but zone based training should bring better results.
They say (per sport do):
Once : 10 minute warm up, then intervalls > 5 Minutes covering all zones
Every Training: 10 minute Warmup as you described
After this you should trust Zonesense. So if its not red, you are not pushing enough
Maybe I try it…
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Because it’s a lagging indicator, interval sessions sometimes don’t even register. A track workout of 400m sprints, with 400m walks may or may not register; 100m sprints almost certainly will not.
Suunto has stated that it needs at least 3 minutes before the data stabilizes.
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@VoiGAS It’s also been problematic for me. I was hoping it would be a good proxy for lactate threshold testing, but that doesn’t appear to be the case. For my workouts, I do Norwegian style sub-threshold intervals of:
- 10×3:00 @ ~12K effort
- 5×6:00 @ ~HM effort
- 3×10:00 @ ~30K effort
I’ve got my efforts dialed in fairly well based on a long history of racing, so I’m confident if I were to lactate test, I would not be surprised by the results. But when I look at the ZoneSense data, sometimes it shows a V̇O₂ max response, sometimes it doesn’t. Even though the paces aren’t changing.
I’m willing to give some grace for heat, fatigue, niggles, and other things, but the data varies too wildly to make any type of reliable or consistent decisions. Sometimes it claims my AnT is around 160 bpm, sometimes 140 bpm. I honestly am not sure how I’m supposed to interpret that.
I want it to work, as it would be great validating how I’m training, but I’m not sure how to interpret the frequent large day-to-day and within-workout swings.
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For me I use it on my easy runs and I look at it after the workout. Usually it gives good results for me in those cases.
However, I struggle to make it really useful in races: There you have no 10 minute warmup. Even more so, if it is a trail race, how to make the values actionable if it lags at least 2 minutes? -
@2b2bff Right, I think in a Race the first 10 minutes are critical. A lot of people get too excited and start too fast. This is where I check the Heartrate very often. Not possible with Zonesense in the first 10 minutes and I am also not sure if it would react fast enough too warn me pushing too hard
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Right, I think in a Race the first 10 minutes are critical. A lot of people get too excited and start too fast
iirc Joaquin Pérez suggests a 10-minute warm-up before the race and saving that session to have a specific calibration for that day. Then you can start the race at full intensity.
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Right, I think in a Race the first 10 minutes are critical. A lot of people get too excited and start too fast
iirc Joaquin Pérez suggests a 10-minute warm-up before the race and saving that session to have a specific calibration for that day. Then you can start the race at full intensity.
I’ve done back to back sessions where the first was 10-15m, ended and started a new session, and ZoneSense still waited another 10m on the second session before reporting.
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@raven afaik if I correctly understood the stuff I’ve read ZS in the next 10 minutes, considering that we start with a higher intensity, would not be able to perform the calibration and therefore, at the end of the 10 minutes, it will use the calibration data previously performed. However, the 10 minutes are still necessary for ZS to allow the body to reach homeostasis.
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@snow My overall point is, in my experience, there’s never any session where you’ll get a “live” ZoneSense reading in minutes 00:01-10:00 whether it’s your first session of the day or your second or later session. If you stop and save a workout and immediately start another, there’s still a 10m wait.
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@raven Did you try it with the same activity type for Warmup? So no Crosstraining - Running, but Running - Running?
I heard this should work. Not happy with it as running activities also creates VO2MAX values.
Race S
Vertical Titanium Solar
Ambit3 Vertical
Eon Core -
I analysed about 80 of my runs (mostly aerobic) for which ZS had values for the aerobic threshold.
The root mean square error (relative to the mean HR) was 5.6 bpm. The mean HR was 142 bpm. My old (2-years ago) lab-tested threshold was 138.
Unfortunately I think ZS is not precise enough to use to update zone boundaries.
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