I use an HRM but really, it's mostly for entertainment. Since I'm 62 the max on my HRM is 160 bpm (guess Garmin calculates this when I entered my age?) but I've recently done sustained efforts in the 170's and up to a 187 max (sprinting on a long/steep climb).

So when the thing starts beeping and someone I'm riding with asks "Why does your Garmin keep beeping?" I reply, "It's telling me I'm over my max heart rate . . . just ignore it!"

Rick / OCRR