Well, the 220-age thing doesn't work well for me. At close to 60 that'd put my max heart rate at 160! While it's been a year since I've checked, last summer I would hit into the high 180s when maxing out. When I look at LSD riding (@ 75%), I should be riding with a heart rate of about 120. My heart gets going 120 just getting my gear on let alone spinning a pedal.
Now I do know that if I ride regular my heart rate will come down somewhat but still, unless I'm hitting at least the 150s I'm hardly starting to sweat.
So, either this heart rate max thing is way over-rated (based upon age) or my physiology is just plain screwed up (which it could be). Oh and I have been Cardiac tested a number of times but only stress tested once and that wasn't all that stressful. I've never done a "pedal till you drop" measuring heart rate and I supposed VO2Max. I think that'd be interesting.