Heart Rate Tells the Story (Fitness Fact # 4)

You already know that your heart beats faster when you’re exercising and slower when you’re resting. But just how much faster and how much slower does it beat?

The main objectives of aerobic exercise are to get you breathing faster and speed up your heart rate. But to get the most benefit from the aerobic exercise, you must keep your heart beating within a certain range—not too high and not too low.

To make sure that happens, you need to know three numbers:
Resting Heart Rate (RHR)
Maximum Heart Rate (MHR)
Target Heart Rate (THR)

FIRST, determine your RHR by counting how many times your heart beats in one minute. You can feel your heart beat, or pulse, anywhere there’s an artery near the surface of your skin. The two best places are on either side of your neck just below your jaw line (carotid artery) and the inside of either wrist on the thumb side (radial artery).

Here’s how to measure your RHR:
Relax. The best time to measure your RHR is in the morning before you get out of bed.
Lightly press your index and middle fingers on the arteries in either your neck or wrist. (Don’t use your thumb to measure your pulse rate because the artery in your thumb pulses so strongly that you may count its pulse by accident.)
Count the number of pulses you feel in 10 seconds. Begin your count 0 – 1 – 2 – 3 – 4 – and so on.
Multiply by 6 the number of pulses you counted in 10 seconds. (For example, 12 pulses x 6 = RHR of 72 beats per minute, or bpm.)

As your aerobic fitness increases, your RHR will go down. This lets you measure your beginning aerobic fitness level and chart your progress over time.

SECOND, calculate your maximum heart rate, or MHR, using this formula:220 – YOUR AGE = MHR
Example: If you are 14 years old, your MHR would be 206 beats per minute (220 – 14 = 206 bpm).

THIRD, now that you know your RHR and MHR, you can calculate your target heart rate, or THR. There is an upper “intensity” and a lower “intensity” THR. Between them is the zone in which your heart and lungs get the most benefit from aerobic exercise. Your THR zone is generally between 60% and 85% of your MHR. Use the following formula (The Karvonen method) to calculate your upper and lower THR: ((MHR – RHR) X % INTENSITY) + RHR = THR

Example: If your MHR is 206 bpm and your RHR is 72 bpm, you would calculate your upper and lower THR as follows:
Lower intensity (60%):
((206 – 72) x 0.60) + 72 = 152 bpm
Upper intensity (85%):
((206 – 72) x 0.85) + 72 = 186 bpm

This means your THR zone is 152 bpm to 186 bpm. Take your pulse periodically as you exercise and adjust the intensity of your exercise to stay within the 60% to 85% range.

When you first start doing aerobic exercise, aim for the lowest part of your THR zone (60%). Slowly build up to the higher part of your THR zone. After six or more months of regular exercise, you may be able to exercise comfortably at the 85% upper intensity. However, remember that you don’t have to exercise that hard to stay in shape.
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