I’m doing the HR drift test on day 1 of the training plan to determine my AeT. I use a Polar H10 chest strap to get my HR measurements. In July 2022 I have tested VO2Max along with AeT/AT in a lab. At that time my AeT was measured 138 bmp and AT 160 bpm (level run) 158 bpm (incline run). I think my general fitness improved after July, but went down somewhat in the winter months, so I can’t say if my fitness is better or worse compared to July.

I first did an outdoor run following the steps of the HR drift test. 15 min warm up to 138 bmp and then I started recording. I tried to keep my HR at that. The HR went up and down somewhat during the run, and averaged at 137 bpm. I uploaded the activity to RunAnalyze and got +0,8 % for Pa:Hr.

I was a little surprised by the result and did the HR drift test again a few days later on a treadmill. I warmed up to 20.5% grade at 2.5 mph. My starting HR was about 143. I keep the treadmill at the same grade and pace for the next hour. According to the indoor HR drift test instructions, I should take the average HR of the first half and the second half. My average for the first half was 144 and my second half was 146, barely any drift.

From the numbers it seems like my AeT is somewhere above 144 and I should redo the test with a higher beginning HR. However, the perceived effort when walking on the treadmill during the test was already beyond the “easy and relaxed—a conversational pace”. I tried talking to myself during the test, and found my breath ran out in about 3 seconds. I was also breathing from my mouth instead of my nose.

Did I miss something here?