I think the 220-age is a "guesstimate" based on folks with not much training base. I'm 57, walk a lot, bike a little, and at an HR of 163 I'm working hard but not winded by any means. My last longish ride I was doing from 150-170 pretty much the whole 4 hours. Once on a hill I felt I really needed to get off the bike and walk it for a bit, heart really pounding its way out of my chest. Took a peek at the HRM and it was at 180. I've been up there since with a similar sensation. So I figure that's my max. Or near it: even then, I wasn't about to keel over, wasn't dizzy or in pain.