What is happening? Should I try again (for the 6th time, LOL) with a higher HR?

Yup. It took me about 5-6 tries to get it right when I first started doing these protocols (but for me I was going too hard and getting too much drift). Generally I think the advice here is if your drift is negative or well under the 5%, you should re-test at a higher HR until you get closer to that 5%, without going over.

But a few questions:

1) Why did you test yourself today at a lower HR (~110 bpm) when you already tested yourself and got a negative drift at 130 bpm in the Spring? If you demonstrated that 130 is under your AeT, then it’s not surprising testing 20 bpm below that is not raising your heartrate at all in the second half.

2) How did testing in the Spring at 130 feel? Did it feel very easy and sustainable like you could do it all day? Did you do a sufficient warm up? If the answer to these questions is yes, then I would try again at a higher HR. If not, then I would try again at the same HR with a longer warm up. From what I read here (and in my own experience) HR can be very high as your body warms up for the first 15-20 minutes and then when it settles in it might lower for the second half producing your negative result.

My only other advice is if you do test at a higher bpm, take it easy, like try 135 instead of jumping to 145 or something. The beauty of an AeT test is that (hopefully!) it’s not hard to recover from, and you can test again relatively soon!