What is measuring your heart rate good for?

There are a number of new fitness bands, smartwatches, and smartphone apps that will also measure heart rate. These data are valuable because heart rate provides a good measure of cardiovascular fitness, which basically is the ability of your heart and circulatory system to provide oxygen (and nutrients) to your body organs and muscles. Having good cardiovascular fitness decreases your risk of cardiovascular disease (CVD), stroke, high blood pressure, and diabetes.

Technically, cardiovascular fitness is "the amount of oxygen transported in the blood and pumped by the heart to the working muscles, and the efficiency of the muscles to use that oxygen [Wikipedia]". Focusing on the heart, the idea is to "work out" your heart muscles so that they can beat stronger and hence less frequently. This can increase exercise tolerance enabling you to exercise more which can cause weight reduction and lower your cholesterol. In addition, cardiovascular fitness can reduce your blood pressure because the heart is beating less frequently.

The simplest measure of cardiovascular fitness is your resting heart rate i.e. your heart rate when you are not exercising i.e. right now as you read this blog post. The lower the heart rate the better. The normal adult resting heart rate is 60 to 100 beats per minute, whereas a well-conditioned athlete may have a resting heart rate of 40 to 60 beats per minute.

One can also measure heart rate during exercise. For example in the Rockport walk test, the patient walks briskly on a treadmill for one mile. Then the workout time and heart rate are recorded and compared against age-adjusted averages.

The way to improve your cardiovascular fitness is through aerobic ("cardio") exercise. These are exercises that increase your heart rate and breathing but are not too strenuous; you should still be able to talk to someone while doing it. Examples include running, jogging, hiking, biking, and swimming. Remember, the CDC recommends either 150 minutes of moderate-intensity aerobic exercise (e.g. brisk walking) each week (~30 minutes/day) or 75 minutes/week of vigorous-intensity aerobic exercise (e.g. jogging).

A more quantitative way to gauge your aerobic workout is to calculate a target training heart rate. First determine your maximum heart rate which should be approximately 220 minus your age.  Then the range of your target rate should be between 50 to 85% of the maximum. So if you are 50, then the maximum heart rate is about 170 beats per minute, and you should strive for a heart rate when you exercise between 85 to 145 beats per minute.

Let's say you don't plan to purchase one of the fancy new activity trackers or smartwatches. You can still measure heart rate the old-fashioned way as described by the following instructions from the Cleveland Clinic (Figure 1):

1A. Place the tips of your index, second and third fingers on the palm side of your other wrist below the base of the thumb.
1B. Or, place the tips of your index and second fingers on your lower neck on either side of your windpipe.
2. Press lightly with your fingers until you feel the blood pulsing beneath your fingers. You may need to move your fingers around slightly up or down until you feel the pulsing.
3. Use a watch with a second hand, or look at a clock with a second hand.
4. Count the beats you feel for 10 seconds. Multiply this number by six to get your heart rate (pulse) per minute.

Normal heart rates at rest:

• Children (ages 6 - 15) 70 – 100 beats per minute
• Adults (age 18 and over) 60 – 100 beats per minute

Figure 1. Measuring your heart rate (pulse)