I'm 51 and, when cycling or running, (I do about 120-150 km per week) I find myself comfortable at over 160 BPM and even at 180 BPM for a few km or when climbing a long climb (5-8 km, which means going at 175-184 for 40 mins). During short bursts I can peak at 189 without feeling dizzy or bad in any way other than without air for a while. My average heart rate for a normal workout can be between 150 and 160 and I can have a conversation-filled ride in which I average 145-150. Of course all this goes against the different ways of calculating the max heart rate (which for my age is supposed to be, depending on the method, around 170). What gives? Am I endangering my health? is max heart rate relative. Does anyone know cases similar to mine? Thanks in advance
Your max heart rate is the maximum your heart will beat at and can be determined with a stress test designed to push your heart to that level. All of the formulae are for estimating a maximum heart rate based on a statistical analyses of measured max heart rates.
Those estimators really should include confidence intervals, but that kind of complexity goes over the heads of most people and tends to be omitted in articles aimed at the public. For example Gellish 2007 indicates their formula fits 95% of their population ±20 bpm. Note that is of the population being studied. Some experiments involve much larger populations than others. It is not unusual for one study to indicate how they utilized a different subject selection method in order to avoid some bias they believe a prior study had.
Until they devise a study that measures whatever determines maximum heart rate more directly than age and gender, the estimators are going to be rather broad and of limited utility.
As for whether your activities are healthy, consult your doctor - suitable stress tests should let them determine what are acceptable intensities for you.