I know think my Half Monty threshold HR is too high, which I thought before, based on the great info that’s now included in the new app under Athlete Profile. I see it says 88% of peak 1-minute heart rate in during the Ramp portion of HM = Threshold HR. Well, even with my max HR being high for my age at 188, that would mean mathematically, based on that equation, my threshold HR could only go up to 165 and change. I know I didn’t maintain 188 for a minute, so all in all, I can’t have a 176 threshold HR based on HM. I did have a few noisy spikes in HR above my max HR, so I assume that’s what skewed it. That being said, in the 20 minute portion of the test I was able to maintain the recommended HR between 160-165ish. My previous 4DP said I was at 156, so thinking for sure I’m somewhere between 156-166 for threshold HR, and right now 160s feels probably accurate but not entirely sure. Curious to hear thoughts. I will likely do 4DP in the next week, so that will probably give me a more honest answer.
My HR has done that in HM before. Turned out my battery in my heart rate monitor was flat and I also got some weird spikes. Redid Half Monty and it came back down again.
Lactate Threshold Heart Rate varies day to day, and is highly influenced by a variety of variables like how rested you are, how much caffeine you have consumed, how hot and humid it is, etc.
In the article, ‘The Simple Guide to Heart Rate Training,’ we see that Zone 4 often confused with LTHR is broken into two categories, Zone 4a and Zone 4b. Zone 4a, or Sub Lactate Threshold is defined as being at 95-100% of LTHR or 91-100% of FTP. Theoretically, if you are both fit and well rested (ie have trained smartly), one can sustain this level of effort for 60-90 minutes. While Zone 4b, or Supra Lactate Threshold, is 100-105% of LT or 100-110% of FTP. And again, if fresh and well trained, one can maintain this level of intensity for 30-60 minutes.
Ok, that should help illuminate day to day LTHR variability, and HR Zones.
Lastly, Half Monty is doing its best to make an approximation of your Lactate Threshold Heart Rate. In the article, ‘Ask The Experts: What is the Half Monty Ramp Test?’ This testing protocol is doing its best job at delivering an accurate and precise approximation of your LTHR by combining the data from your Peak 1 minute heart rate with the 20 minute sub threshold heart rate data. If you wanted truly precise LTHR you would need to go to a sports science lab to do a Lactate Threshold Heart Rate Test that would involve a lab tech pricking your finger at regular time intervals with regular increases in load on the bike while recording your heart rate data.
Thanks everyone, really appreciate it! I’ll see what I get the next time I knock out the 4DP, probably in the next week or two 
In addition to @WahooCoach_Corey answer I’ll add that the mean and median values for 1min relative to Threshold heart rate are 92.4% and 92.5% respectively. However, we do see correct values (meaning accurate peak 1 minute and accurate threshold HR) ranging from 84.3% up to 96.2%
Can you point me to where you are seeing the 88% value? That is not correct so I want to fix/edit that so we don’t confuse folks.
sure thing, it’s in the Athlete Profile on my iPhone: Screen Shot 2021-10-04 at 1...
Helpful to hear the additional fine tuned details here Thank you!