I was trying to avoid the details and more thinking about the general idea of pace @ AeT improving and how it relates to the ten percent test! But if it helps, I’m 39m, about 3 years since I first cracked open TFTNA. The first season I trained about 400 hours using a very extended version of the 24 week mountaineering plan here. When I started I was very aerobically deficient. My AeT was 140 bpm and 11:00 min/miles. 400 hours was a bit too much with foot problems popping up at the end of the season. After that we had our first child so my volume has been similar if not a bit less with parenting duties and a family illness taking time from training.
Recently I’ve worked with a non-UA coach (my wife’s triathlon coach! Kind of like the Carolyn Parker husband-and-wife client podcast except the other way around) towards improving my flat and downhill running speed because that is where I get dropped in my trail running races. I’m at about 25 miles a week of running plus about two hours of zwift riding, mainly to avoid the foot issues which has worked well for me.
With respect to dropping that much time of my AeT pace: 1) I think in the April test I could have gone a bit faster – I note the decoupling was very low with the 9:10 min/mile pace; so perhaps if I were more diligent I would have tested again in that same period at a higher pace/heartrate; and 2) I was actually very surprised by my latest test, which prompted me to post here. I was very much expecting a higher heartrate at a different pace before I started the workout. My plan was to test closer to a 165 heartrate and what I thought was going to be something like 8:30 min/miles or so. Instead, as I finished my warmup I was comfortably nose-breathing at the ~7:30 pace, but felt right at the edge of the “all-day” pace in terms of speed. My watch said 155 bpm. So instead of pushing it, I just stayed at the same pace and figured we’d see if I could keep the heartrate steady for the full hour, and I got the 4.5% Pa:Hr result.
I suspect I improved significantly in my running economy due to spending more time on flat routes and the speed workouts, which I’m thrilled about. But I suppose I’m wondering if @Eddie is right and my AeT HR is stagnating because of even 10% Z3 volume. Or alternatively, is this result in the realm of AeT being a moving target with fatigue and stress and maybe I should just test again on a different day?
Also re: Aerobic workouts being repeatable the next day – I think it’s also noted that as one’s Z2 pace gets faster, it becomes difficult to recover from the efforts (and pounding!) and more Z1 volume is necessary. About half of my aerobic volume is Z1/recovery pace according to Training Peaks.