As was stated - get a stress test.
We have discussed HR zones here - the 220-age is a guide and not a rule. My max is about 190. I routinely cruise at 145. I can stay at 160 for long climbs and sprint at 185. I use the HRM as a tool during training run where I am have difficulty with motivation low up too early.- to push myself or on some training runs to hold myself back so I don't blow up to early. The doc who did my stress test said my chart looked like the perfect text book plot, so he was not concerned.