Typically, your target heart-rate zone is between 50 percent and 85 percent of your maximum heart rate, the maximum number of times your heart should beat in a minute without dangerously overexerting yourself. Your heart rate can tell you so much about your body — how fit you are, how much you’ve improved, and whether you’ve recovered from yesterday’s workout. Your target zone can tell you what heart rate to aim for during a workout.
The point at which your body switches from using oxygen as its primary source of energy to using stored sugar is referred to as your anaerobic threshold. When you’re in poor physical shape, your body isn’t very efficient at taking in oxygen, and you hit your anaerobic threshold while exercising at relatively low levels of exercise. As you become more fit, you’re able to go farther and faster, yet still supply oxygen to your muscles.
At the low end of your target zone, you’re barely breaking a sweat; at the high end, you’re dripping like a Kentucky Derby winner. If you’re a beginner, stick to the lower end so you can move along comfortably for longer periods of time and with less chance of injury. As you get more fit, you may want to do some of your training in the middle and upper end of your zone.
So how do you estimate your maximum heart rate? A common method for determining maximum heart rate for men is to subtract their age from 220, and for women to subtract their age from 226. Keep in mind that this formula gives you only an estimate. Your true max may be as many as 15 beats higher or lower. Also, this formula is generally used for activities during which your feet hit the ground. (To estimate your max for bicycling, subtract about five beats from the final result; for swimming, subtract about ten beats.)
Using that easy formula to find your max, find your target heart-rate zone by calculating 50 percent and 85 percent of your maximum. Here’s the math for a 40-year-old man:
220 – 40 = 180
This is his estimated maximum heart rate.
180 x 0.50 = 90
This is the low end of his target zone. If his heart beats less than 90 times per minute, he knows that he’s not pushing hard enough.
180 x 0.85 = 153
This is the high end of his target zone. If his heart beats faster than 153 beats per minute, he needs to slow down.
Okay, so now you know how to figure out your target heart-rate zone. But how do you know if you’re in the zone? In other words, how do you know how fast your heart is beating at any given moment? You can check your heart by taking your pulse manually or using a heart-rate monitor.