I am in the same boat; I have ADS and am running the same race. My AeT is 140 bpm and LT is 176 when tested (with portable lactate analzyer) 8 weeks ago. I have been training 90% of my time under 140 since. That 36 bpm spread is large and is unlikely to have been shifted much (recently I did a drift test at 145 bpm and I drifted more than 5%)(I must need to do more volume, although I’ve been hovering around 5 hours running 4 hours biking per week). I hear the advice above and elsewhere:
-Start conservative
-Mostly ignore HR
-Race on feel
I have one twist: I rolled my ankle a few times this spring and have been strengthening and running on it since. But I have been very conservative on the downhills, most of the technical descents (>20% with rocks) my HR falls to Z1 and is only slightly faster than my uphills. I am also a fast twitch athlete. So my plan is to keep the HR in Z2 for the first ~20 minutes then allow to climb to low-mid Z3. On the descents I will take it easy and let it fall back into Z1-2. If after the first half of the race I feel I can push it harder I will let it climb to mid-upper Z3, but not hit LT. Basically, using my slow descents as rests and then relying on my FT muscles to be engaged for the ascents. However, all sorts of factors could affect HR on race day: caffeine, elevation, adrenaline and other endorphins, heat etc. So basically I plan to do the above except make decisions based on perceived effort and use HR as a sanity check knowing that it could well be elevated. I hope to finish around 5.5 hours which would be split about evenly between Z3 and Z2-Z1 efforts. If I were expecting 8 hours I would probably not let my perceived exertion be above what would normally be low Z3 at least for the first half.
All in all I will use the above as a rough guideline from which I will allow myself to deviate based on feel during race day.
Good luck and I’ll see ya out there!
Brian