Originally Posted by Eric F

I agree 100% that getting the body to true max HR on a bike is hard. Really hard. In my racer-boy days, I saw max HR numbers at the end of a sprint in a race, where I was putting every last watt of power into my bike for a long as I could possibly tolerate. It's a level of intensity that is deeply uncomfortable, and takes practice to understand how to push your body to that far. In my early-30s, I saw 207 a couple of times. When I quit racing at 35yo, it was 204. At 55, I don't inflict that level of suffering on my body very often, but the most recent time I did (desperate to stay with a group over the top of a short climb), it was 189.

For me, figuring out my zones is about how my body is reacting. I can feel the shift from zone 2 to zone 3 @ 149bpm. I know an extended FTP effort is going to put me at right about 170bpm. I can last about a minute at 180bpm, maybe a little more if I'm having a good day, but I also know I can repeat an effort like that quite a few times.