In the Zone

Achieving Your Target Heart Rate

By Erica K. Perkins, Fitness Director, UVA

You are moving, sweating and breathing hard, but how do you know if you’re exercising at the appropriate intensity for your age and fitness level? For most of us, there is a range of heart rate intensities that are considered safe and effective for promoting benefits.

Read on to find out why it’s important to monitor your heart rate and how to determine your target zone. It just takes a little math.

Resting Heart Rate (RHR) this is simply the number of times your heart beats per minute (bpm) while at rest. It can be an indicator of how fit you are. A fit person usually has a lower resting heart rate than an unfit person. As you exercise regularly, your resting heart rate will decrease. This is because your heart has become stronger, enabling it to pump more blood with each contraction and allowing more rest between beats. The best time to take your resting heart rate is in the morning for a full minute.

Maximal Heart Rate (MHR) is the highest number of times your heart can contract or beat in one minute during maximal physical exertion. It is not the maximum one should achieve during exercise. This number is related to your age because as we grow older, the heart slows. To estimate your maximal heart rate, simply subtract your age from the number 220.

Target Heart Rate Zone (THRZ) is the range between two numbers indicating the number of beats per minute (bpm) at which your heart should be beating during aerobic exercise. For most healthy individuals, this range is 40 to 85 percent of your maximal heart rate. So, if your maximal heart rate is 180 bpm, the low end of the range (40 percent) would be 72 bpm, and the high end of the range (85 percent) would be 153 bpm.

Do the math

In order to make the target zone more accurate for people of all ages and fitness levels, you can factor in your resting heart rate using this equation:

(220 – age) – RHR x intensity + RHR

For example:

A 40 yr old with a RHR of 70, the THRZ would be 114 bpm to 163.5 bpm

220–40 = 180–70 = 110 x .40 (40% of max. heart rate) = 44 + 70 = 114

220-40 = 180–70 = 110 x .85 (85% of max. heart rate) = 93.5 + 70 = 163.5

For easier monitoring during exercise, divide each of these numbers by 6 for a 10 second count.

Fine-tune your zone

If you’re just beginning aerobic exercise, aim for the low end of the zone and pick up the intensity as you become more comfortable with your workouts. Aim for the higher end of the zone if you are more fit or training for competitive events.

Keep in mind that the target heart-rate zone is recommended for individuals without any health problems. For those taking medication that alters the heart rate should be sure to consult your physician for recommended exercise intensity. In addition, THRZ is an estimate, so listen to your body and reduce the intensity if you feel you are working too hard.