Your target heart rate is a range that predicts how hard you work during exercise. Tracking your heart rate helps you find a challenging exercise intensity while also helping you to avoid pushing beyond a safe level.
Target heart rate zones are based on a percentage of the fastest rate that your heart can beat per minute. This is known as the maximal heart rate and can be calculated using the following formula:
maximal beats per minute (bpm) = 206.9 - (age in years x 0.67) *
Once you know your maximal heart rate, you can find your target heart rate range for exercise. For moderate-intensity exercise, aim for a heart rate that is 50 - 70% of your maximal heart rate. For vigorous exercise, aim for 70 - 85% of your maximal heart rate.
Below is an example equation for a 40 year old person exercising at moderate intensity.
206.9 - (40 x 0.67) = 180 bpm maximal heart rate
180 x 0.50 = 90 bpm (at 50% maximal heart rate)
180 x 0.70 = 126 bpm (at 70% maximal heart rate)
To exercise at a moderate intensity, this person should keep her heart rate between 90 and 126 bpm throughout the workout.
Exercise intensity and target heart rate vary from person to person. Beginners should exercise at the lower end of their target heart rate range and increase intensity slowly as the body becomes more fit. Aim for an intensity that meets your goals for calorie burning, challenges your current fitness state, and is safe and tolerable. The best intensity is one that is challenging enough to benefit your heart, lungs, muscles and bones, while not being so intense that you risk injury.
*Another popular equation is (220 - age in years), but the American College of Sports Medicine recommends this more accurate equation.