Workout with the help of heart rate monitor

Written by: Vojko Strojnik, Ph.D.

Heart rate measurement is invaluable in planning and control of exercise for endurance. Measurement of heart rate is simple. It can be done manually by measuring the pulse on the neck or wrist and counting the number of beats in a given time interval (for example, counting for 15 seconds, then multiplying the count by 4 to get the number of beats per minute). You can use a variety of electronic pulse monitors which measure pulse continuously and store the data for later analysis. Another important association is correlation of the pulse with the intensity of exercise. Pulse is closely related to the consumption of oxygen, so pulse measurement allows us to determine the relative consumption of oxygen or intensity of movement.

Intensity of movement is an important manifestation of physiological adaptation of the organism, so it is beneficial to know the intensity zone in which you are exercising. Measuring the pulse allows trainers and athletes to develop a more detailed workout plan. When losing weight, you can set your target zone for the most efficient use of fat as the energy source, for example. Although it is easy to monitor pulse, you must also be aware that it is not totally reliable.

The most important factor in relying on pulse is determining the maximum heart rate. Frequently, maximum heart rate is calculated using the formula:

Maximum pulse frequency = 220 – age in years

Although this is true on average, individual variations may be over 20 beats per minute. The only reliable manner to determine maximum pulse frequency is through a gradual increase of intensity of movement while monitoring the pulse. When the pulse ceases to rise and intensity of movement continues to increase, we have reached maximum pulse. Unfortunately, such testing presents a health risk (if your heart is not healthy) and is very strenuous. While the above formula is valid for running, the top frequency for cycling is lower by 10 beats on average (210 – age), and for swimming by 15 strokes (205 – age).

For even greater individualization of exercise with the use of pulse, you should also be aware there are differences in the lower pulse frequency at rest. Big differences exist among individuals as well as significant changes due to the choice of exercise. Research has taken these differences into account by using the Karvonen Formula to define the functional heart reserve. Functional reserve of pulse correlates very well with use of oxygen across virtually the entire functional reserve (Figure 1).

Figure 1. Relationship between pulse and consumption of oxygen by intensities of movement

As an example, let us determine a target workout zone between 60 and 70% intensity for a 30 year-old person who has a resting pulse of 60 beats per minute, and the maximum pulse of 190 (220 - 30) beats per minute. If we take only the maximum pulse into account when determining the target training zone:

Lower boundary 60%: 190 x 0,6 = 114,

Upper boundary 70%: 190 x 0,7 = 133.

According to the Karvonen formula, however, the same target zone is:

Lower boundary 60%: (190 – 60) x 0,6 + 60 = 138,

Upper boundary 70%: (190 – 60) x 0,7 + 60 = 151.

As you can see, the difference can be significant. In practice both calculations are being used, so it is necessary to carefully read the exercise instructions to determine how the intensity intervals were calculated.