It looks like the average for the first half is 162 and second half 168. Average of first three minutes is 155, and drift is 3.7%. Probably that 155 is a good number to use unless I did something wrong. If you have lap averages that would be easier to look at and a graph is helpful too.

Okay, thanks. That’s much easier.

1) Don’t worry about the fluctuations in heart rate. That’s normal. Heart rate is just a global measure of stress so your body will respond to the stress it’s experiencing. Second-to-second changes in heart rate aren’t meaningful for training, just the averages and general trends.

2) I think you’re safe to use ~160 as the upper limit for your AeT (i.e. top of Zone 2). The drift in the last hour was exactly 5%: (168 / 160).

3) Don’t fixate on small bpm changes. As I said above, they’re not meaningful. We don’t have a device that can measure what’s actually going on in your body, so we have to use proxy measurements like heart rate. They are rough guidelines, so you should assume that they are imprecise.

Just one question for the future: how did you come up with the 160?

1. View the workout;
2. Click and drag from the end of the workout (~1h25′) back to 55′. Note that the average HR is 168;
3. Click and drag from 55′ back to 25′. Note that the average HR is 160;
4. 168 / 160 = 1.05. So the drift at that speed on that grade is 5%, the limit for an aerobic capacity intensity.

Note that it is at the limit, so as Rachel said, training at 155 would work just as well. Plus you wouldn’t be cutting it so close.

It does look that way. How did you test your AnT?