The commonly used formulas for calculating maximum heart rate for a given age are totally inadequate for ages greater than 50. That formula was developed based of a population in which seniors were under represented. The most accurate such formula I've seen is something like 206 - (age X .65). The other short coming of the mathematical models is they all assume a "normal" resting heart rate 60 - 80), and it ignores those of us with resting HR's < 60 due to training. Finally, whatever number you get from whatever formula you chose, it's a statistic guideline, not a limit.

I do have a heart condition, as in a mammary artery masquerading as my left anterior descending. Long story I won't address here. Point is I still routinely exceed my "predicted" max for sustained periods. My cardiologist has has seen my print outs from Strava and he's fine with what I'm doing.