Assessing Your Intensity

Heart rate is easiest to take using the radial pulse. Take your pulse on the wrist using the index and middle finger of the opposite hand, applying gentle pressure. If you use your thumb, which has its own pulse, you will get a false rate. Practice by taking a 30-second pulse, but during exercise you will take a 10-second pulse immediately after completing the activity. Multiply the 10-second count by 6 to calculate your heart rate in beats per minute (bpm). Your heart rate decreases rapidly once you stop exercising, so a 30-second heart rate underestimates your actual exercise heart rate.

Table 3.1 gives 10-second counts for target heart rates so that you can memorize your target 10-second count. Since taking a radial pulse has some room for error and using a 10-second count can exaggerate this error, aim for the target 10-second count, plus or minus 2 beats. For example, the training heart rate identified in the sidebar is 139; the target 10-second count would then be approximately 22 to 24, or 132 to 144 bpm. Trying to reach an exact heart rate is impractical and frustrating, while aiming for a target heart rate range is much easier.

If you take medication that alters your heart rate response, have problems taking your pulse, or want a simpler approach to estimating intensity, you can use what is called your RPE—rating of perceived exertion (Robertson and Noble 1997). For this method, estimate your exercise intensity on a scale ranging from 6 to 20 points. The scale is related to your heart rate; if you multiply the scale value by 10, it equals your heart rate. An RPE of 14 (exercising somewhat hard) corresponds to a target heart rate of 140. Therefore, if I determine that my target heart rate for an intensity of 60 percent is 140, my corresponding RPE should be 14. Rating of perceived exertion is not as accurate as measuring your heart rate, but with practice you will be able to estimate your response to exercise. If you are not on medications that affect your heart rate, you should take an exercise pulse at least once and relate it to your perception of work. Otherwise, use the descriptions of the levels to help you determine if you are at the correct exercise intensity: 13 to 14 = somewhat hard, 15 to 16 = hard, 17 to 18 = very hard, and 19 to 20 = very, very hard.