Before embarking on one of the following workouts, you must establish some working numbers. Most heart-rate training programs ask you to find your maximum heart rate and calculate the percentages for your four training zones from there. Typically, you subtract your age from 220 to establish your MHR, but such calculations are often inaccurate, failing to consider the differences among age groups and fitness levels—even differences within an individual moving from one sport to another. And maximum heart rate has more to do with genetic traits, such as the size of your heart, than with your level of fitness. A better solution, says fitness expert Jay Blahnik, is to learn to recognize the four workload zones—recovery, aerobic, threshold, anaerobic—and then glance at your HRM to find the corresponding heart rates.
To find your targets, strap on an HRM and warm up as you normally would for your ski, ride, or run. Gradually increase your pace, evaluating how your body feels after three to five minutes at each level of intensity. When you reach each of the zones below, note your heart rate.
Recovery: You feel you could carry this pace for 60 minutes or more.
Aerobic: If you had to, you could maintain this exertion level for 20 to 40 minutes.
Threshold: You could do this for no more than ten minutes.
Anaerobic: This hurts. You feel like you can do it for a minute, maybe two at most.
Do the sport on the same terrain two or three times over a few weeks, says Blahnik, and when some common numbers begin to appear, assign them the following values: recovery, 60 percent of your max heart rate; aerobic, 70 percent; threshold, 80 percent; anaerobic, 80 to 90 percent.