i dont know about your formula, have a good time with that..
I assume you will get a heartrate monitor that saves data,
for downloading to your home PC to get the numbers..

I'm 64, and don't get ego points off
climbing a steep at a high heart rate, slope,
when I can lower it promptly
by walking my push-bike up that same hill.

freightraininguphill is into somewhat of his Sisyphus project, with that Bike Friday .