One way of monitoring physical activity intensity is to determine whether a person’s pulse or heart rate is within the target zone during physical activity.
For moderate-intensity physical activity, a person’s target heart rate should be 70 to 85% of his or her maximum heart rate. This maximum rate is based on the person’s age. An estimate of a person’s maximum age-related heart rate can be obtained by subtracting the person’s age from 220. For example, for a 20-year-old person, the estimated maximum age-related heart rate would be calculated as 220 – 20 years = 200 beats per minute (bpm). The 70% and 85% levels would be:
- 70% level: 200 x 0.70 = 140 bpm, and
- 85% level: 200 x 0.85 = 170 bpm
Thus, moderate-intensity physical activity for a 20-year-old person will require that the heart rate remains between 140 and 170 bpm during physical activity.
Generally, to determine whether you are exercising within the heart rate target zone, you must stop exercising briefly to take your pulse. You can take the pulse at the neck, the wrist, or the chest. We recommend the wrist. You can feel the radial pulse on the artery of the wrist in line with the thumb. Place the tips of the index and middle fingers over the artery and press lightly. Do not use the thumb. Take a full 60-second count of the heartbeats, or take for 30 seconds and multiply by 2. Start the count on a beat, which is counted as “zero.” If this number falls between 85 and 119 bpm in the case of the 50-year-old person, he or she is active within the target range for moderate-intensity activity.