At the risk of seeming argumentative: 1. I think the 220-age formula was widely used before the internet. I swear I remember learning it in an exercise physiology class back in the 1970s, and 2.
any formula you use will only be an approximation, will not fit someone who is not "average", and will thus be vulnerable to being declared "bogus".
AND... thanks to the internet it is pretty easy to find out that there are other formulas that may yield more accurate results.
