When talking or learning about exercise, you often hear the word “intensity”. Intensity refers to how hard a person works to do a select activity. The two most often examined intensities in exercise are moderate and vigorous intensity. For many individuals, determining if you are working at a moderate or vigorous intensity may be tricky. The body’s physiological response to exercise is a steady increase in activity with an increased intensity of activity. Thus, a great way to estimate your relative exercise intensity is through your heart rate and prediction of your target heart rate zone (THRZ).
Percentage of maximal heart rate (MHR) is based on simple exercise physiology, which predicts an individual’s MHR from the age based equation: 220 – age. For example, the MHR for a 30 year old individual would be equal to 220-30 = 190. Target Heart Rate, also known as percentage of Maximal Heart Rate Reserve, is an aerobic method, also based on the MHR prediction, used to estimate an individual’s THRZ. THRZ is the intensity range that will produce training effects on the heart if maintained for a sufficient length of time (i.e. 20-30 minutes). Typical THRZ for a moderate activity is 40%-59% of MHR, and for a vigorous activity, 60%-84%1. For healthy individuals, the American Heart Association recommends individuals set their THRZ between 50%-85% of their MHR2. Individuals who are new to exercise, previously sedentary, rehabilitating or have medical problems should aim for a lower THRZ and consult with their physician or an exercise professional before starting exercise.
Selecting your THRZ:
- 80%-90% of MHR – improve performance, high intensity exercise (no medical problems)
- 70%-85% of MHR – established aerobic exercisers, currently active most days of the week
- 60%-75% of MHR – intermediate level exercisers
- 50%- 60% MHR – previously sedentary, medical problems, new to exercise
If you are looking to exercise within your THRZ, below is a sample calculation for an established 30 year old exerciser aiming for a THR Zone of 70% – 85%:
- MHR = 220 – 30 years old = 190
- Upper Limit (85%) = MHR x .85 = 190 x .85 = 162 beats/min
- Lower Limit (70%)= MHR x .70 = 190 x .70 = 133 beats/min
- Target HR Zone: Lower Limit beats/min to Upper Limit beats/min (133 beats/min to 162 beats/min)
If you are new to exercise, during the first few weeks aim for the lower part of your THRZ. Gradually aim for a higher training percentage of your THRZ. A great way to monitor your heart rate during exercise is with a heart rate monitor. There are many forms and styles available for purchase. The American College of Sports Medicine offers a great resource for Selecting and Effectively Using a Heart Rate Monitor.