The Heart Rate and Treadmills

On the treadmill, your heart rate helps tell you if you're exercising at the optimal intensity for an effective cardiovascular workout. Most treadmills come with built-in heart-rate monitors for convenience; however, accuracy varies widely on different machines, so it's a good idea to check your pulse manually, as well. If you're new to exercise, consult your physician before starting a new treadmill program.

You can estimate the intensity of your treadmill workout by using maximum heart rate, or HRmax. First, subtract your age from the number 220 to find your HRmax. During light aerobic activity, a suitable place to start for beginners, you should reach 40 to 50 percent of HRmax. During moderate aerobic exercise, which burns more calories and builds greater endurance than light cardio, aim for 50 to 70 percent of HRmax. And for vigorous cardio, the most efficient calorie-torching exercise and suitable for reaching peak fitness levels, aim for 70 to 85 percent of HRmax. As an example, a 40-year-old person has an HRmax of 180 beats per minute and should have a heart rate of 90 to 126 bpm during moderate exercise.

Typically, walking on the treadmill at speeds slower than 3 mph will get you to the right heart-rate zone for a light cardio workout, while walking between 3 mph and 4.5 mph will usually get you into the moderate heart-rate zone. Walking at an incline can get you to a moderate or vigorous level, depending on the slope, while racewalking at 5 mph or higher, jogging and running all get you to the heart-rate zone for vigorous exercise. No matter what your heart rate says, however, slow down or take a break if you feel lightheaded or out of breath.

The heart-rate sensor attached to your treadmill may be handy, but don't count on it for accuracy. Most electric heart-rate monitors come with a margin of error, and the devices on cardio machines are often less reliable than handheld versions, according to fitness instructor Mary Miriani, in an interview with IDEA Health and Fitness Association. Miriani also notes that using heart-rate monitors incorrectly may lead to false readings -- so if you do use one, learn proper technique.

To perform your own reading or to check your treadmill heart-rate monitor for accuracy, learn to take your own pulse. Pause the treadmill and place two fingers lightly over the pulse point on your wrist. Count the beats for 20 seconds -- treadmills often display a countdown while paused, so use it as a timer if you have no stopwatch. Now multiply the result times three to find your beats per minute.