Originally Posted by
McFlyRides
I don't have a PM at this time, and it's been ages since I had a lab test. So I use perceived effort to define my zones, focusing on what feels like the anaerobic threshold. The other zones are percentages of that AT HR, not percentages of a theoretical max HR.
Essentially, below that AT HR, I'm breathing hard, forcefully, but controlled. Below that HR, I can continue for some time even though it's quite hard.
Above that AT HR I'm gasping, the walls are closing in, and I can't continue at that pace more than a few minutes.
For me, it's easier to find that anaerobic threshold by experience and perceived exertion than it is to know what my max HR is. I'm 50+, so the formula says 170 is my max. In my races last year I saw 184 in one race and 188 in another. For me it takes a finish line sprint to see those numbers--the adrenaline, the tangible goal of going faster to defend against or catch another rider.
As you have proved, 220-age is a terrible way to determine max. HR. My numbers are similar to yours (55yo, 189max).
Although I use both power and HR when I ride, paying attention to how my body is reacting is how I've determined where my various threshold numbers are.