I just did a steep treadmill test a week ago and found a 5.2% drift at 140bpms. So my aet is barely 140.

So imagine my surprise when I did this test again yesterday, this time outdoors, on one of my flat 90 minute Aet runs. I had a gain and loss of less than 50 feet on roads. I ran for 1:30 targeting 140bpms, my average HR was actually 142 and my Pa:Hr was between -0.26 to 1.5 depending on which section I highlight. Since that is very much below 3% (for 90 minutes not just 60) does that suggest my Aet is actually much higher than 142? Perhaps even high 140s?

That would be awesome but it would also surprise me that I have a higher Aet outdoors than in the treadmill test I wrote about above. Would this suggest I am much more efficient at running than hiking uphill on a treadmill? Or maybe it just goes to show that some days we perform better than others and HR is variable day to day. I have also read here that one can run at Ant for an hour without a drift so maybe that explains this too.