I track my H/R using a Polar HR monitor. However, it's not necessary, but I just like tracking certain things during my rides and runs. One thing you learn when you first start monitoring your HR is that it's not set in stone; it's extremely variable.
First thing, forget the 220 – your age, or any other formulae. If you HR matches any formula, then it's just a coincidence and if you are just starting to get into shape, chances are your max HR will change. It also depends on how well you're feeling, when I'm sick, my max HR can either be higher or lower than what it is normally; furthermore, it is not the same for when I ride a bike or go for a run.
I also like checking my resting HR, which also varies, especially if I'm sick or recovering from several hard days of exercise.
This is a pretty good article on the myths behind HR:
5 Max Heartrate Training Myths, Busted | Bicycling
Max HR is largely untrainable, and determined by genetics—some of us have hearts tuned like humming birds' while others have the slow ‘n steady type.
“But it’s not an indication of performance," Golich says. "If your max is 200 and someone else’s is 190, it doesn’t mean one of you is the better athlete." In fact, he’s worked with numerous talented athletes at both ends of the spectrum.
It's good to remember that everyone’s max HR does drop as they age—but again, that doesn’t mean you’re losing fitness.
However, this is a longer, but more detailed version and it shows just how formula for max HR is NOT based on science; it's more of a thing the fitness industry picked up and ran with. Very good article:
http://www.nytimes.com/2001/04/24/he...nged.html?_r=0
In preparation for a medical meeting , Dr. Haskell culled data from about 10 published studies in which people of different ages had been tested to find their maximum heart rates.
The subjects were never meant to be a representative sample of the population, said Dr. Haskell, who is now a professor of medicine at Stanford. Most were under 55 and some were smokers or had heart disease.