Lactate threshold detected, new zones

Wow congratulations! How did it happen -- were you running with a chest HRM? Did you initiate a Lactate Threshold Test manually from the Run activity or it was a normal run?

I don't remember the *exact* details, but it was automatic--I didn't try to do the test. It just detected it.

I was on a quick 3 mile run (with HR strap). I think I was going for my half marathon pace. Maybe I was going faster than that. Anyways, I figured, as long as I'm running fast, I might as well try and do a bit of a HR Max test at the end because I know there's a hill at the end here and my HR is already elevated. So at the end of the run, I started going into the hill and I pushed it and tried to see how high I could raise my HR. I don't think I hit my max HR but I did gas myself, and at the end of the run it told me it had detected a lactate threshold.

I don't remember the *exact* details, but it was automatic--I didn't try to do the test. It just detected it.

I was on a quick 3 mile run (with HR strap). I think I was going for my half marathon pace. Maybe I was going faster than that. Anyways, I figured, as long as I'm running fast, I might as well try and do a bit of a HR Max test at the end because I know there's a hill at the end here and my HR is already elevated. So at the end of the run, I started going into the hill and I pushed it and tried to see how high I could raise my HR. I don't think I hit my max HR but I did gas myself, and at the end of the run it told me it had detected a lactate threshold.

This is similar to how it happened for me. I use a chest strap HRM and was doing 2 minute intervals. One up a hill totally gassed me and at the end of the run i was given a new LTHR and pace. My HR zones also look to have been remapped. In the same run I also hit a new max HR (which is probably really close to my max) so lots of zone shifting there. Basically the best I can tell is run hard for a decently long time near your max and the watch will start filling in this info.

The Training Effect after that run was pretty high (5.0/3.4) so the watch also told me to go easy for the next 3.5 days. I suspect it was being overly cautious here, but a few slow recovery runs were in order for sure.

I had similar after my first LT was achieved, but the watch gave me a choice to set zones using this info or not to.

If you trust the LT measurements that your watch suggest, and if you are training by heart rate, then you should continue to stay in the same HR zone for comparable runs. I.e., if you prior to the change were doing an easy run at "low to medium z2", then after the recalculated zones, you should still do your easy runs at "low to medium z2". The fact that "low to medum z2" means different numeric values after the change is just an indication that your fitness has improved. The words used to describe the zones ("warmup", "easy", "low aerobic" are just descriptions, they don't really mean anything).

That said, I'm sceptic about the LT measurements provided by my Fenix 5x. It proudly announced it had detected a new LT at 158 bpm and proceeded to update the zone definitions. Less than a week later I had a formal LT test at the local university sports department (blood tests, accurate treadmill, 4 minute intervals etc), and the formal test resulted in 147 bpm which correlates far better with my perceived exhaustion for the different intensities. So I have started to ignore the Fenix when it offers to amend my zones for me.

I wish the watch was smart enough to figure out when i was at/near my LT while running up a hill and not suggest a new "pace" for that LT at the end of a run. I declined it, which is easy to do, but I suspect it would give me a far more generous pace if i was running downhill. This makes the actual pace listed on the watch somewhat useless as it isn't adjusted for elevation or grade. From what I was reading somewhere else, the Vo2 Max stuff isn't taking elevation or grade into account either. That seems like an obvious area to improve.

^^^^ This is exactly why VO2 Max and LTHR aren't calculated when using the Trail Run app. So if you know you're going on a run that involves lots of steep/changing grades, then use the Trail Run app and your stats won't be distorted.

I wish the watch was smart enough to figure out when i was at/near my LT while running up a hill and not suggest a new "pace" for that LT at the end of a run. I declined it, which is easy to do, but I suspect it would give me a far more generous pace if i was running downhill. This makes the actual pace listed on the watch somewhat useless as it isn't adjusted for elevation or grade. From what I was reading somewhere else, the Vo2 Max stuff isn't taking elevation or grade into account either. That seems like an obvious area to improve.

Actually, VO2Max does take into account elevation changes.