BHViking: Are you on Strava? Here's the link to that workout, and you can see my HR data.
https://www.strava.com/activities/3806257238/overviewI have no problems with the protocol, but I have a lot of experience training with the HRM. My HR is pretty consistent. Here's what I do:
Using Garmin Connect (it's baaaack), I set up a "Workout" that I can send to the Forerunner which has the entire process already programmed in. So all I have to do is click the lap button as I move from stage to stage. So I start the watch and warm up. When I'm ready to run the 140 segment, I click the lap button. The watch beeps when I get to 135, signaling me that I am getting close to the limit and then beeps another beep when I hit 140. I never look at the watch throughout the entire test. I just try to keep my effort "between the beeps." If I haven't heard the "high-end" beep for 30 seconds or so I pick it up slightly... as soon as it beeps I pull off just a fraction. But the whole lap is within a 4-5bpm range. At the end of the lap, I click the lap button and my 90 second rest is programmed in. Then lap button again and I'm off, this time the beeps come as I hit 145 and again at 150. So that's how I manage to stay so consistent. Just trying to stay within the beeps. Doing it in this way resulted in HRavges of 138,48,58,68,78 for both the June and July tests.
So I have measures in place to prevent the over/under shooting... plus, as I said, I'm really accustomed to training in this way.
The course I run is NOT a flat track; there is some slight, short rise and fall, but I'm really dialed in to my effort vs HR so it's not an issue. Plus, as long as I always use the same protocol, the relative results have value.
This is done with a chest strap HRM. It is dependable and consistent.
I don't see anything wrong with the way that you did it, keeping pace constant and seeing what HR you were at. It's all just for relative comparative purposes, so just as long as the protocol is repeatable, I'd say you're good.
RRR: I haven't had a beer in several weeks, though I do have a single glass of red wine every evening. I find it easy to drink one glass of red wine, but less easy to have one, single, lonely brewski. And with a 4:30am wakeup... maybe in me younger days...