I’ve recently started using a Garmin chest strap to monitor my HR, and am making a real effort to establish an AeT after using the wrist-based monitor to guesstimate it.

I have two recent runs, both long and at a pace that felt easy. Course is almost identical. The difference in mileage accounted for by adding a few extra loops on flat city streets. Area is mostly flat with a few short easy grades.

Both runs are under 5% on TP pa:hr. (Free, so I’m not able to use the aerobic decoupling feature to eliminate warmup HR)

Run A:
Time – 1:27:40
Distance – 9.8 mi
Avg pace – 8:57/m
Avg HR – 171 BPM
pa:hr – 4.73%
Temp 79-88 F

Run B:
Time – 1:16:11
Distance – 7.8 mi
Avg pace – 9:44/m
Avg HR – 154 BPM
pa:hr – 0.38%
Temp 69-81 F

My question is, which of these runs is more representative of my AeT pace and AeT HR, respectively? Run A was hot and humid, and I felt myself really cutting back my effort to keep my HR low in the heat.

Is there any meaningful data to be drawn from these two, or is the answer to just do another long run under cooler conditions?

Background- 29 y/o m with a 7 year history of physical, low intensity but long duration forestry work. The work incorporated lots of hiking under a load. I began training seriously about 2 years ago and am coming off a three month break in training. My training hours over the past 2 years are 3-6 hrs/ week, but there’s a lot of uncaptured ‘training’ hiding in there because of my work.

The past three months I’ve been behind a desk, and so no hidden hours there- big ole 0.