Ride steady hard for 30min (time trial). Your approximate LTHR is last 20min average (source).
Thanks, I’ll have a look to see if I’ve already got a ride that fits the bill.
With a HRmax of 181bpm, 70% will be 127bpm. I’d suggest this is the lowest you’d want to be training at. Your LT1 will probably be more like 140-145bpm but only a proper test would tell (as others have said). Personally I’ve a similar HRmax to you and I notice my breathing starts to increase at around 140bpm.
I think Seiler suggested 0.7 * HRmax for polarized training as you will definitely be below LT1 at that level but it should still be just hard enough to have some training effect. You’d couple that with maybe 10 to 20% above 0.8 HRmax and probably closer to 87-92% HRmax. - Obviously over a week’s training not necessarily in the same session.