I am 63 years old, 200 lbs., excellent condition. My HR stays at 140 on level in fast group ride. Mountains when hammering steep stuff I can sustain 160-1 for 5 minute blocks. The other day when going uphill at maximum effort with young powerful racers, I looked at the Polar and saw 172.....I actually held it for quite a while (over a minute). Based on that, I believe that 174-5 could be considered my MHR. The old 220 minus your age is too general to use for serious self analysis. I think it's a good idea to schedule a stress treadmill test and learn about your cardiac health (I did it 2 months ago and it's just a great psychological boost when you find out how OK your heart is!).