Calculating Exercise Intensity

You've been gradually increasing the amount of time (duration) you spend on your aerobic workout. Now it's time to increase the intensity of your exercise. Intensity is how hard you work during exercise. Before stepping up the intensity of your aerobic exercises, you’ll need to know ways of calculating your exercise intensity.

How can I benefit by learning this skill?

Knowing ways to calculate the intensity of your workout can ensure that you don't overdo it. It also provides a starting point for setting exercise goals.

How do I perform this skill?

You can monitor your heart rate to know how hard you're working out. The easiest way to do this is by wearing a heart-rate monitor, which shows your heart's beats per minute (bpm). You can also check your heart rate without a special device by taking your pulse. To take your pulse, place the pad of one finger lightly over the front of the opposite wrist, just below the thumb. Count the pulses for 15 seconds and multiply them by four. (For example, 20 pulses in 15 seconds is 80 bpm.) You'll use this number to track how hard you're working out. If you're not able to feel your pulse at your wrist, you can place the pads of two fingers on the carotid artery, located on the side of your neck.

To target the intensity of your workout, obtain your maximum heart rate (MHR) by subtracting your age from 220. Then multiply by a percentage between 50 and 85 percent. If you're just starting out, shoot for 50 to 60 percent of your MHR. Eventually you can progress toward a high-energy workout by targeting between 75 and 85 percent. (Refer to the target heart rate example for calculating an exercise target.)

Another way to check how hard you're working is to rate how you feel when you're working out. This method uses a rate of perceived exertion (RPE) scale. While exercising, choose a number between zero and 10, where one means you're hardly doing anything (no exertion), and 10 means you're at your maximum exertion. Shoot for an RPE between four and six. Your RPE represents the amount of work you feel in your muscles and how hard you're breathing.

Are there other recommendations I need to be aware of?

Check your pulse often at first while exercising to check that you are meeting your intensity target. Also, rate your intensity from zero to 10 (your RPE) and track it when you check your heart rate. Your RPE should equate closely to your exercise heart rate. In other words, at 60 percent of your maximum heart rate, you may feel that you're working with an RPE of five. Advancing to 80 percent of your maximum heart rate will cause your RPE to rise, perhaps to a seven or eight.

After a while, you may find that you only need to keep an eye on your RPE, as it will give you a good idea about what your heart rate is doing. Use your current exercise levels to set goals. Goals can help make your aerobic exercise program meaningful and fun.

What should I watch out for while doing this skill?

Beginners, sedentary people, and aging adults should target between 50 and 60 percent of their maximum heart rate. This percentage can safely go up as your body adjusts to a longer workout with greater intensity.