It’s common to need to slow to a hike on uphills to keep efforts under AeT. The one piece of feedback I would offer is to feel free to spend time in Z2. The guidance to avoid Z2 is when working in that zone places too high a strain on the musculoskeletal system.

I was in a similar boat to you two years ago. My AeT was in the mid 150s and it felt slow to stay there. However, things have changed enormously since then. My AeT now sits in the low-to-mid 160s and I now train primarily (around 85% of my time) in Z1 (mid to high 140s) because Z2 is tough on my body and can lead to overuse injuries.

You’re doing things right. I would encourage you to stick with it! Use your AeT as a cap for your training but don’t worry too much about the Z1 vs Z2 differentiation. As you get more fit, you’ll realize Z2 requires too much effort and your training load will shift to Z1. Then you will be able to put in longer and longer Z3 and Z4 sessions and your progress will be rapid.

…just assumed that I was not suffering from aerobic deficiency since the bulk of my training before doing the AeT test was at a Zone 3 effort for me.

This is precisely why you probably have ADS. Unsupported Z3 training is how people destroy their aerobic systems.

@dahlindan: By “unsupported,” I meant in too high a proportion in relation to the more important aerobic training of Z1 and Z2.

Think of Z3 and above as salt. The right amount makes a meal taste great. Too much will ruin it.

Or as debt when investing. The right amount will juice your returns with an acceptable amount of risk. Too much debt and you can lose your original investment.

The problem is that most people gauge the “right” amount of high intensity by how they feel. “I’m working hard so I must be getting fitter!” That’s almost never the case. Anything that feels like “such a good workout” is probably using up aerobic capacity rather than building it up.

As a real-life example of proper training, when Moses Mosop ran his first marathon in 2h03m, only 3% of his training leading up to that marathon was above Z2. (The average intensity of a ~2h event is typically just above aerobic threshold, the top of zone 2.)

Granted, Mosop’s Z2 is really @#$%ing fast, but at a metabolic level, most of his training was quite “easy” and way below the upper limit of Z2. Even more so, 78% was below Z1.

In contrast, newcomers combine a mistaken gratification bias (fatigue means fitness!), underdeveloped aerobic systems, and friends with the same problems. So almost everyone goes too hard too soon together. With social pressure and unrealistic expectations, most people have a really hard time going slow enough to build up their aerobic systems. They overdo Z3 and quickly hit a hard plateau. Then they double down and go harder! Cue downward spiral…

Sandcastles: A Model of Endurance Training

Is the goal of aerobic training to become faster at the same AeT HR, to raise the AeT HR, or both?

Both. Initially, both will improve, but HR will eventually stop. The narrowest AnT HR / AeT HR gap that I’ve seen (in more than one person, but after years of training) is just under 5%.

I see some elite runners doing mountain runs with HR between 130-140.

That’s meaningless on its own. HRs are like fingerprints; they’re unique to their owner. You’d need to know their threshold HRs for that information to be relevant. That said, if the runs are long, then they are likely at a low percentage of AnT HR.

After four months of shifting my training to ~3/4 Z2 workouts, I have seen my AeT rise from 145 to 151. My speed at 145 is the same, which surprised me. I have noticed other improvements like being able to do hilly neighborhood runs at Z2 (previously I’d spike to Z3) and my Z3 and Z4 mountain efforts are quicker.

That makes sense. Improving your base will also improve your speed at higher intensities.