I'm curious about my heart rate lately too. My brother died young and completely unexpectedly of a heart attack recently, so I've been taking a somewhat morbid interest in my heart function that I previously couldn't have cared less about.

So I borrowed a HR monitor and on my first ride (dirt road in the woods, plenty of hills) I was idly reckoning out my max HR to be ...lemmesee... 220-37=183. Next hill I hit there were some fit young men ahead just begging to be passed and before I knew it I had hit 185.
And on similar occasions (that is, fit young men, slow old women, or just anybody, actually, that NEEDS passing ) I've easily hit 180-185 and kept that rate for 10-20 seconds. So the formula obviously is inaccurate for me.

So from that I'm guessing my max is 190 or higher. I know you're supposed to test it individually, but it sounds like such a hassle, throwing yourself up a hill 3 times til you almost puke?

Another surprise was that with a resting HR of about 55 (evening, not morning) I still have a much higher HR (75-100) just moving around the house. Weird.