Target Heart-Rate Zone

A target heart-rate zone is a range of heart rates used to represent a desired level of aerobic exercise intensity. Rather than prescribing one exact heart rate, the zone provides lower and upper boundaries within which heart rate can be monitored during activity. Target zones are commonly expressed as percentages of maximum heart rate or heart-rate reserve .^1,2

One method calculates the zone as a percentage of maximum heart rate, or HRmax. For example, a commonly used general guide places moderate-intensity activity at about 50 to 70% of HRmax and vigorous activity at about 70 to 85% of HRmax. These percentages represent approximate exercise-intensity ranges rather than precise physiological boundaries for every individual .²

Another method uses heart-rate reserve, or HRR, which is the difference between maximum and resting heart rate. A chosen percentage of HRR is added to the resting heart rate to obtain a target heart rate. Because this method incorporates both resting and maximum heart rate, it differs mathematically from simply taking the same percentage of HRmax .¹

A target heart-rate zone should not be confused with maximum heart rate, which represents the highest heart rate attained during maximal effort. Maximum heart rate can be measured during an exercise test or estimated using age-based equations, but such equations have substantial individual error. Heart-rate responses can also be altered by medications and medical conditions, so a generic target zone does not always accurately represent an individual's exercise intensity .^1,2