Simple advice, IGNORE your heart rate, the "max heart rate" calculations are a bunch of junk and completely and utterly irrelevant.
Just for curiosity's sake, I checked my heart rate at the end of my first 1-Mile race in nearly 40 years (38 years 7 months to be exact) on January 1st this year, and it was right bang about 190, but per the "max heart rate" calculations the maximum rate for a 56 year old "should be" 164.
Soapbox...
The sooner the running community can quash the stupid 220-age formula the better for everybody who believes in heart rate training (I do not and probably never will).
End Soapbox!