Recurring problem regarding detected Running Lactate Treshold

Garmin thinks you don't give everything and in perfect conditions on a perfect day you would be able to run 5:34 for 5km. I don't know you, but I have the same problem, it's always too optimistic.

HR zones set to MaxHR or LTHR? If you use a chest strap then set it to LTHR for better accuracy.

Thanks, the zones are set to MaxHR. I could try, but the detected RLT BPM on my watch is obviously wrong (way too high), and if changing zones to LTHR instead it's reasonable to think that the zones will be based on wrong value (watch RLT). How will that improve the accuracy of RLT BPM and pace? Have you experienced it yourself?

If you're using an HRM strap then the strap knows your max hr and will automagically set LTHR zones to that. After that future zones work (as long as you use theHRM strap) will use LTHR.

RichardB said:

If you're using an HRM strap then the strap knows your max hr and will automagically set LTHR zones to that. After that future zones work (as long as you use theHRM strap) will use LTHR.

Sorry, but none of this makes any sense.

- Max HR is auto-detected by the watch (or set by the user). The watch can use either the built-in optical HR or an external HR monitor to auto-detect max HR. You don't need a chest strap for the watch to know or guess your max HR

- OP already said they set their max HR, why would they need another way for their max HR to be determined?

- LTHR zones, by definition, are based on LTHR, not max HR. Yes, LTHR can be guessed as a % of max HR, but that's not what Garmin does when you set your zones to be based on LTHR

- The strap doesn't set LTHR zones, zones are set by the watch (or the Connect app) when you change zone settings (or when the LTHR/max HR detected/set on the watch changes, for zones based on LTHR/max HR).

- If you set your watch to use zones based on LTHR, they'll be used whether or not you use an HRM strap

Maybe you're thinking of the past situation where a chest strap was required to use the guided lactate threshold detection test? Or maybe you're suggesting that wearing a strap results in a more accurate detection of LTHR? That's not what you said though.

A better suggestion along the lines of this comment would be to somehow obtain a reliable lactate threshold estimate (maybe by doing a manual "guided test" [*] or by getting it measured in a lab), setting that value in the watch, and setting zones based on LTHR.

[*] e.g. https://run.outsideonline.com/training/getting-started/do-it-yourself-lactate-threshold-testing/

flocsy🤠 said:

Garmin thinks you don't give everything and in perfect conditions on a perfect day you would be able to run 5:34 for 5km.

You're missing the point where OP's max HR is set to 174 bpm, but watch detects a lactate threshold of 170 bpm.

170 / 174 = 98%

A lactate threshold that's 98% of max HR is extremely unrealistic.

For context:

https://runnersconnect.net/how-to-calculate-your-lactate-threshold/

Most research has found that your lactate threshold heart rate is typically around 80% to 90% of your maximum heart rate.

Lactate threshold is also said to be the HR / pace that most runners can sustain about 1 hour. Iow, Garmin is saying that OP should be able to run at 98% of max HR for a solid hour, which is also extremely unrealistic.

It seems that whatever algorithm is used to detect LTHR maybe doesn't take max HR into account. (Kind of like how in some cases the race predictor might show a slower pace than what you've actually run irl. e.g. Someone has a 5k race prediction of 20:30, but when they run 19:55, the race predictor isn't automatically updated to the faster time. The data that the watch collects and generates isn't always consistent, when you look at the big picture.)

The issue with the 3:54/k 5k prediction vs the 4:05/k 5k reality is peanuts in comparison, as everyone is used to Garmin's race predictor being a little optimistic.

When it comes to the race predictor and VO2 Max estimate, I've always found that the relative trends are more valuable than the absolute numbers (which can't be taken 100% seriously).

Do you have any activity examples that set these LT detected values?  The only way it is going to give a 170bpm threshold... is if you were running for some about of time and it detected that as your Threshold.  COULD be that your threshold is very near you max HR (especially if your max HR isn't super accurate or was from a non-race effort , or on a cold day, early morning, etc)  Most people greatly underestimate their 'real max'.   Also you could have had some bad HR readings that day causing the issue.  Even straps are susceptible to errorr (static etc), no where do you explain what the structure of that days 'detected LT' run was... or what the HR looked like... was it maybe a long downhill section... was it even steady/good effort to detect a LT?.... etc  

For instance I had a great 5k in heat, getting chased, wanted to win age... hammer down... dang near blacking out after.  My Max at the end was 194... I hadn't seen above 187 in years!   Figured max had dropped after 10yrs of training.

So yes at glance you seem right to question your watch.  However... without some of the missing info that is super important (long term HR and training data)... hard to say.

Do you have any activity examples that set these LT detected values?  The only way it is going to give a 170bpm threshold... is if you were running for some about of time and it detected that as your Threshold.  COULD be that your threshold is very near you max HR (especially if your max HR isn't super accurate or was from a non-race effort , or on a cold day, early morning, etc)  Most people greatly underestimate their 'real max'.   Also you could have had some bad HR readings that day causing the issue.  Even straps are susceptible to errorr (static etc), no where do you explain what the structure of that days 'detected LT' run was... or what the HR looked like... was it maybe a long downhill section... was it even steady/good effort to detect a LT?.... etc  

For instance I had a great 5k in heat, getting chased, wanted to win age... hammer down... dang near blacking out after.  My Max at the end was 194... I hadn't seen above 187 in years!   Figured max had dropped after 10yrs of training.

So yes at glance you seem right to question your watch.  However... without some of the missing info that is super important (long term HR and training data)... hard to say.

Contact Garmin Support. But they'll likely tell you it's the new "improved" threshold updates.  It now estimates LT not just on HRV during an activity, but also on HR and pace from recent runs, and VO2Max. HRV is only "factored into the overall estimate".  It will even update the estimate when you do a slow run, where you never came close to a threshold HR/pace.