I will add to the conversation by reporting what I did. A few years ago, I was running a little again. Not much, mind you, but I wore a HR monitor for some of it. I don't think any of my runs were more than a mile, if that. At the end of one of my short runs, I decided, knowing how far I was from home, to pick up the pace gradually so that, by the time I got home, I'd be running as fast as I could for the last 100 yards or so. And I think that's where I hit 179 on the Polar app once I'd downloaded the data. My age would have 64 or so at the time. It was my crude approximation of what I thought they do on treadmill tests in a lab. No humans or animals were harmed during the course of this study.
I honestly didn't expect it to be accurate, but this was shortly after I'd started using the HRM, and I was working with a max calculated by formula and knew my max HR was higher than that, so I just wanted a higher number to plug in. A real number would have been nice but, for free and for how easy it was to "test," at least I had something I knew was more realistic. I also remembered, a decade or two earlier, hitting 184 on a HRM doing the same thing, but at that time I was actually running distance regularly - I did the same thing then, but it was at the end of a 5-mile run instead of the shorter one a few years ago.
These tests are interesting data to have about one's self. I hope to do the telomere (or something along those lines) and also this HRM-in-a-lab-done-by-pros tests sometime in the relatively near future.
The thing that I liked most about the Jack Daniel's book was that VDOT (his term) number was based off racing performances. I never considered what it actually represented in physiological terms. The recommended paces for intervals, repeats, tempo runs, etc., all worked great for me. I've never been a particularly good distance runner, but to take 35 seconds off my best 5k time at age 45 was pretty cool to be able to do, and I'm confident it was training according to the guidance in that book that was what changed and made a difference for me.
FWIW, his guidance for what he called a tempo run was that it was limited to 20 minutes, regardless of your pace. As I was a 20-minutes-and-change 5k runner, it was easy for me to run to the 3-mile mark of a local 5k course. Pace was, if memory serves, about :30/mile slower than my then-current 5k race best, and you only did it once a week, no more often than that.
-S-