HR during Z2 - when do you call it?

[WindWarrior]

My endurance pace HR is from when I trained by HR, and refined over time. Some info on my field testing here:

Can an endurance athlete build/maintain a meaningful strength foundation/base and be fit?

Estimated starting in 2016 and refined year after since. Part of my methodology here: It’s not my VT1 or LT1 because I’ve no plans to get tested. It’s my pragmatic lower aerobic threshold where I can go out and do long 8-16 hour rides, wake up the next day and feel normal, and two days later continue training as normal. Like here, 14 hours into a double century: [image] That’s about 3-4bpm below my estimated HR at lower aerobic threshold. Easy but not too easy pace. That was on a Saturday…

and threshold HR here:

Training w/power for first time

Started with HR in 2016 and it served me well. Quickly figured out that I blew up when spending more than 3-5 minutes at 165bpm. Then figured I could hold something like 155-160bpm for 20 minutes, then 30 minutes, then 40 minutes, and eventually worked my way up to 50 minutes. Also figured out I could do long 1-3 hour climbs in the mountains at around 135-145bpm, and somewhat easily finish centuries at that heart rate. Added power I found power zones correlated really well with those heart rate…