Lactate threshold comparison to lab test

Pretty cool! For the watch only estimating the LTHR based on 2 runs, I'd say that's reasonably good estimate. I think it gets more accurate as it collects more samples over time. Impressive that the VO2 Max was pretty close to spot on. Thanks for posting your findings!

Thanks for sharing the info!

I have also done lactate tests in a lab, and if I remember correctly the lab test gave me the first and the second lactate thresholds. LT1, when lactate production passes a certain level, and LT2 when lactate can not be ventilated, and therefore is accumulated. It is my understanding that Garmin gives LT2 in the guided test. It is at least very close for me. LT2 is higher, and seems to correlate well to the figures you have got. Didn't you get LT2 from your lab test?

The watch had estimated LTHR based on more than 2 runs. I had some earlier numbers that were slightly lower but only posted the 2 most recent data points.

The UC Davis lab report shows LT1 = 173 and LT2 = 186. I had assumed that my watch was giving me an estimate of LT1 = 181. The Firstbeat Analytics documentation on lactate threshold doesn't clearly differentiate between LT1 or LT2. But it does state "For the average runner, it occurs well below 90% of their maximum heart rate". I'm an "average runner" and my max heart rate is 199, which implies my LTHR should be below 179. Thus I conclude that my watch is probably trying to estimate LT1 and not LT2.

For training purposes I was mainly just interested in LT1 since that should be the highest effort I can sustain on a long run without building up a lot of fatigue. LT2 is less relevant since during training I can only keep that up for a few minutes anyway.

Ah, gotcha. Pretty cool that they do this at UC Davis, I live nearby in the next county over. Might check out doing this for myself soon.

LT2 is the heart rate where you should be able to stay at, for an hour.

I am using my tested LT2 as the threshold in my HR zones (threshold based, not max HR based). LT1 is the start of Z4 and 102% of LT2 is the end of Z4. Using this, it is quite easy to do threshold training session, by simply staying in zone 4. From LT1 and just above LT2. Btw, my LT2 is a bit above 90% of max HR.

And yes, LT1 and below is my Z3, where I can have long run (bike) sessions. 

In an all-out maximum half marathon race effort I was able to hold 185 bpm for an hour, which is close to what the lab report showed as LT2 = 186. But that's kind of irrelevant for training purposes due to the high residual fatigue.

There are a bunch of different methods for setting heart rate training zones so we might be referring to different things. The most common method is to set 5 zones with LT1 as the top end of Zone 2 and LT2 in Zone 4. I've never heard of anyone using LT1 as the start of Zone 4 in a 5 zone model because it would make Zone 4 too wide to be useful for structured training. But I suppose if you're using a 7 zone model then it could work?

I had to re-read my lab report. It do not mention “LT1” at all, but rather my threshold for a full marathon in addition to my lactate threshold (LT2). The first one is different from LT1. My mistake. Sorry for any confusion.

So my z4 is basically set as you describe. 

But coming back to LT1 I read this interesting article written by the5krunner: https://the5krunner.com/2021/02/25/important-training-news-dfa-alpha-1-new-threshold-discovery-method-with-hrv/

My Epix2pro, in a recent lactate threshold test, estimated LT HR 154 and LT pace 5:19min/km. My recent average Half-Marathon pace is 5:18min/km. In my recent 4h marathon (pace 5:43) garmin connect estimated that I ran for 55:12 mins above 154 pulse. Therefore I think that garmin-LT refers to LT1 (or aerobic threshold) and not LT2 (anaerobic threshold).