How to Calculate Heart Rate Reserve

Heart rate reserve should be calculated when gauging workout intensity. The formula is simple: Subtract your resting heart rate from your maximum heart rate.

Despite the simplicity of calculating HRR, it's not always accurate and researchers have found that the "talk test" may be more effective when creating exercise programs.

What exactly is heart rate reserve (HRR)? An August 2014 ‌Mayo Clinic Proceedings‌ article defines HRR as the difference between your resting heart rate and your maximum heart rate. It's used when calculating exercise target heart rates. The formula is:

HRR = HR (max) - HR (rest)

Your heart rate measures the intensity of your workout — the higher your heart rate, the higher your exercise intensity. If you feel that you're pushing yourself in a workout, your heart rate is likely on the high end.

According to Mayo Clinic, you can gauge intensity with heart rate measuring technology or by calculating how hard your heart is beating during physical activity. You'd begin by calculating maximum heart rate by subtracting your age from 220.

Say you're 30, then your maximum heart rate should be 190, the average number of times your heart should beat per minute during physical activity.

If you'd like to calculate your desired heart rate zone, the point at which your heart is being exercised but not overworked, you can use a simple formula, known as the Karvonen formula. For light physical activity, you can aim for 30 to 40 percent of HRR; for moderate, you can aim for 40 to 60 percent; and for vigorous, you can aim for 60 to 90 percent, says an article published in January 2017 in the ‌British Columbia Medical Journal‌.

Begin with your maximum heart rate — found by subtracting your age from 220 — then calculate your resting heart rate by counting how many times your heart beats per minute when you're at rest. It should be between 60 and 100 beats per minute.

1. Calculate your HRR by subtracting your resting heart rate from your maximum rate.
2. Next multiply your HRR by the minimum and maximum percentage.
   
3. Multiply your HRR by 0.6; then add your resting heart rate to this number.
4. Multiply your HRR by 0.9; then add your resting heart rate to this number. The range of these two numbers (HRR x 0.6 and HRR x 0.9) will be your target heart rate zone.

Certain factors, such as medication and health conditions, can affect your heart rate zone. If you have questions regarding your target heart rate zone, consult a physical therapist or doctor.

Conventionally, exercise programs have been created using range-based protocols, such as HRR. But research — by the American Council on Exercise, which enlisted researchers in the Department of Exercise and Sport Science at the University of Wisconsin–La Crosse in June 2018 — shows, using a small sample of 44 university-aged individuals, that formulas may not be the most effective way to develop these programs and determine the appropriate amount of exercise.

Instead, a "talk test," based on what happens to breathing during exercise, may be the best way to monitor your exercise activity. The researchers found that exercise programming using the talk test was much more effective than programming using HRR ranges.

According to the Better Health Channel of Victoria, Australia, the talk test is determined by how much you can talk or sing during exercise. If you can talk or sing without running out of breath, you're doing low-level exercise; if you can comfortably talk but not sing, you're doing moderate-level exercise; and if you can barely speak without running out of breath, you're doing vigorous-level exercise.