How Garmin Changed Its Lactate Threshold Calculation in 2024 – and Why It Matters
Recent changes to beta software for Garmin’s Forerunner models removed the requirement for a chest strap in lactate threshold detection, switching from HRV-based to optical heart rate estimation. This fundamentally changes how several of Garmin’s physiology features work — probably for the worse if accuracy matters to you. For a full explanation of how lactate threshold works on Garmin devices, see the Garmin Lactate Threshold reference page. This article covers the specific change to the calculation announced in October 2024 and its implications.
The Old Method
Garmin’s old method relied on HRV, and, as we know, HRV at sporting exertion levels can only be accurately measured with a decent chest strap.
The Firstbeat method of lactate threshold detection used in Garmin devices relies on the fact that your respiration rate — how hard you are breathing — can be detected through analysis of your heart rate variability (HRV). The process of inhalation and exhalation produces tiny changes in the interval between heartbeats (HRV). When these variations are decoded and combined with other performance data, your device can recognize the simultaneous changes in your heart rate to indicate when you are performing above your lactate threshold. [Garmin]
Bored?, try this: more on HOW Garmin’s fitness Empire Will Eventually Crumble
Firstbeat-Garmin probably assumed some equivalence between the Ventilatory Threshold (VT2) and Lactate Threshold (LT2). With my non-scientist-level sports science knowledge, I seem to recall that VT2 and LT2 are similar enough for this to be valid. In any case, as Garmin says above, they also tweak the data based on other factors.
Related: Garmin’s FTP – Not quite what you think
The New Method
The new beta software somewhat vaguely proposed a change to the calculation, saying, “Lactate Threshold estimates are applied automatically after training with heart rate.“. However, Garmin clarified the details of its automatic LTHR detection, which requires a pre-existing VO2max estimate and a (trail-)run recording of heart rate and GPS.
Related: Garmin VO2max – not what you think
The Issues
It must be wrong to remove the option for us to approve any detected change to LTHR. Training or recording of it can sometimes go wrong, or we might think it’s not representative of our performance, or someone else could have borrowed your watch!
Optical heart rate certainly is inaccurate compared to a chest strap.
This seems like a retrograde move by Garmin when others are using more innovative ways to improve the usefulness and accuracy of determining effort in general and LTHR in particular – I’m thinking particularly of Suunto’s recent DDFA calculations to determine changing performance states during every workout.
Last Updated on 19 March 2026 by the5krunner
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors.
Agree with you chest strap is needed for better accuracy
As I know Garmin they won’t rethink this even if there’s a significant user pushback. I think the best we can hope for is that they’ll add some way to control it better:
1. add back the screen at the end of an activity to NOT accept a new LTHR
2. add a setting to when to perform lactate threshold tests:
– with external HR sensor only
– also with the optical sensor
yep
I compared my Garmin sq hrv wrist reading using a free hrv watch app and compared it to Android fatmaxxer app and H10 chest strap. Readings were identical.
garmin doesn’t produce hrv during workouts from ohr; so…..
plus, from what i’ve heard from others, it’s rare to get hrv at rest from multiple sources to closely match. that doesn’t really matter as its the variance to the baseline that has the scientific validity
And this time FRx55/x65 are lucky because Garmin give a changelog and explanations.
Because F7 Series discover the change and try to obtain explanations weeks before FRx55/x65 new beta, without luck…
yes!
it makes you wonder what is NOT in the changelogs! Because, for sure, everything is not in them.
Lactate threshold on my FR255 hasn’t worked since I started using a Polar OH1 arm HRM.
It made me wonder whether I needed a Garmin branded chest HRM.
Do you know if this is true?
i assume it currently needs an RR/HRV capable source.
so most half decent chest straps – but not the oh1 which i dont think supports hrv
actually the oh1 is one example where the HR data should be good enough for whatever garmin’s new algorithm is
Thanks.
Do you happen to know whether the Polar Verity Sense has RR/HRV capability?
I think it’s basically the same ie no hrv from almost any our during sport