Originally Posted by Machka
I have the heart rate of a 23 year old!!
No, you have the heart rate of a 'however-old-you-are'-old. 220 minus age is ridiculously inaccurate and worthless, as are most other formulas . . . nor is max HR (by itself) a measure of fitness; it's determined largely by genetics and not changed significantly by workouts.
My max HR is 190 which by "the formula" would make me somewhat younger than I actually am if I took "the formula" seriously, which I don't.
Better measure of fitness is seeing % of max decrease given the same effort, or power increase given the same % of max. But not max by itself.