OK, in that case to defend myself against the accusations of ignorance without illustrations from CC, unless you have a cardiac stress test done (under medical supervision) so you know your MHR, then the numbers are meaningless. Just riding a few intervals isn't going to get your MHR without taking yourself to a heart rate where you should be medically supervised. And there are
plenty of formulae out there but if you plug some different ages into those you come out with variations between formulae that are bigger than the differences between training zone heart rates. And that's before you allow for the natural variability in the population at a given age which can easily mean you are 10-30bpm out. Also heart rates running are different from heart rates cycling are different from heart rates for swimming. Its very easy for any individual who has not had a cardiac stress test MHR done to be out on the training zones by one or two zones or more.
So hands up here who has had a cardiac stress test MHR done?
At the end of the day, for most people other than athletes on a proper programme HRM figures are a curiosity of no particular meaning although people seem to enjoy slaving themselves to the numbers. But then some people like to cover themselves in techno-gadgets and some people just like to ride. Polar have a lot to answer for.