Isn’t 220-age utter bunkum?
Yes It absolutely is.
I’m 52, so 220-52 gives 168 bpm. I exceed that almost every time I ride. I must be dead.
I did a CX race last week for 40 minutes with an average heart rate of 183, max was 194.
My working max is 197, which I see a few times per year and get close to probably a couple of times a month. But the highest I’ve ever seen (which I took to be an outlier) was 214.
In my opinion the only way to know your maximum heart rate is to monitor it whenever you do activities and adjust accordingly. As long as you’re not grossly unfit or have a medical condition, pushing yourself a bit is not a problem (particularly if you do it incrementally rather than trying to take large jumps in one go.)