Outside magazine, May 1996
"I got my first heart-rate monitor last year," Kelly McCown says. "It was revolutionary." She may have come late to the party, but the reason seemingly every elite athlete is bleating about using a monitor is that it's the only objective way you have to measure exertion. Of course, it doesn't help if you don't know your maximum heart rate.
The most common way to figure your maximum heart rate is simply to subtract your age from 220 if you're a man, 226 if your a woman. Unfortunately, this formula often yields only the roughest estimate. Because maximum heart rate tends to vary depending on the sport and your fitness level, it's best to test your heart rate, in each of your sports, through exertion (check first with your doctor).
After a solid warm-up, ramp up your pace to the highest level of exertion you can sustain for two to four minutes, checking your heart rate several times. By the end of the interval, it should no longer be increasing. Rest for ten minutes and do it again. The highest number you get should be your maximum heart rate-from which you can calculate the percentage you want to target
during each of your workouts.