Therefore, my average for the first half of the test is 143.5.
And my average for the second half of the test is 150.5.
Don’t average the starting and ending values; let Training Peaks calculate the averages. The rise isn’t purely linear–there will be a lot of fluctuation–so the TP algorithm would give a more reliable average.
Then you want to find the drift in the averages, not the starting and ending values.
2. The treadmill test seems like a weird way to test for AeT. Basically, the whole hour-long test is done with a level of exertion ABOVE what we think is the AeT. For example, in the above test, I started by thinking my AeT is 140, but tested it by running ABOVE 140 for an hour (i.e., by running in Zone 3).
You’re assuming that your estimate is correct. The drift test confirms or denies that estimate.
Rather than focus on heart rate, think about it from the pace side. If you warm-up and then go at X pace for 60′, and if you see an HR drift of 5% or less, then you can assume that that pace is equal to or less than your aerobic threshold. If you are training on the treadmill, use the pace. If you are in variable terrain, use the heart rate.
Heart rate is a stress measurement. So as stress increases so will heart rate. Duration is one kind of stress. By observing many hundred athletes, a decent rule of thumb was developed: if a pace elicits a 5% or less drift in HR, then it’s likely within the aerobic threshold.