HRV (heart rate variability) - everything you need to know!

As an active athlete or someone interested in health, one hears more and more often about the so-called heart rate variability (HRV). But not only laymen are increasingly interested in HRV, also the number of scientific articles is constantly increasing.:

What is heart rate variability?

HRV describes the change in the intervals between 2 heartbeats. It is measured in milliseconds (i.e. one thousandth of a second). The greater the variability (i.e. the more different the individual distances are from each other), the better. Here you can see how HRV is calculated from an ECG:

Why is greater variability better?

Without deeper knowledge, one would assume that it is good if the heart beats as evenly as possible. In truth, however, the exact opposite is the case - but why? Every person has a multitude of sensors in their body that provide important feedback for the control of the heart in order to optimally supply the entire body with blood. The heartbeat is then influenced in its sequence via the autonomic nervous system. If this influence functions well, a strong variation of the heartbeat intervals occurs and indicates relief. If this fine control functions poorly or hardly at all, then the organism is under strain.

Want even more detailed information? Check out our webinar on the basics of heart rate variability here:

History of HRV

The first documented use of heart rate variability goes back to the Chinese physician Wang Shu-ho in the 3rd century A.D., who recognized that a very regular heartbeat indicates poor health. He recognized: "If the heartbeat is as regular as the knock of the woodpecker or the drip of the rain on the roof, the patient will die within 4 days." At that time, the delicate intuition of an experienced physician was necessary to recognize this condition. Today, 1700 years later, there are extremely accurate HRV measuring devices for this purpose.

Areas of application of heart rate variability

HRV is primarily used in two areas: sport and health:

Training according to HRV

To adjust your training according to your heart rate variability, it is necessary to measure it at least 2x a day. For this it is almost mandatory to use a HRV meter that calibrates to your body. HRV values are strongly age and person dependent. Only with a calibrated device you can be sure that training recommendations are exactly adapted to your body. On days when your heart rate variability is high, you can train anything from light regenerative sessions to intense intervals to strenuous strength training. If your HRV is low, then you should do light to no training, depending on how low it is. Good apps show you this clearly.

Detect overtraining through HRV - is it possible?

Yes, you can - if you take at least one measurement every day. You can recognize overtraining by regeneration values that no longer recover. Good HRV apps show you this - here is an example from the Vitalmonitor portal:

Which HRV value is good?

This depends on several factors. Basically, heart rate variability decreases with age. How this looks approximately is shown in the following graphic:

However, as described above, one's HRV can be strongly influenced by one's lifestyle. How this can look is shown in the following graphic:

What devices are available for measuring HRV?

In order to measure heart rate variability, there are basically several different possibilities, which have different advantages and disadvantages:

Floor standing units

This class of devices usually has a built-in ECG and thus a high accuracy. Stand-alone devices are mostly used for short-term measurements. Another advantage is that they are supervised by a professional partner who explains complicated HRV values. Disadvantages are very high costs for such a device and therefore high costs per measurement, because each measurement must be performed and interpreted by a partner. In addition, a single measurement has little significance, since it depends very much on the condition of the day.

Portable devices

These devices have the advantage that they are usually cheaper than other HRV stand meters. Meanwhile, they even reach almost the accuracy of ECG stand devices. In this class of devices there are 2 subcategories:

• Devices that send results directly to an app: These HRV measurement devices have the advantage that results are available immediately after a measurement. In addition, smartphones and tablets are usually used as evaluation devices, so there are no additional hardware costs. The associated apps present the evaluation clearly. Better devices (such as the Vitalmonitor Nano) are calibrated to the user's own body through regular morning measurements and thus offer greater accuracy and better evaluations.

• Devices that record data and are later evaluated: Here, the recording usually takes place over 24 hours. You receive a device together with an explanation from a partner and start the measurement the next morning. The advantage here is that a whole day is recorded. The disadvantages are that
  - a partner is necessary for the evaluation & explanation
  - the statements depend on the state of the day
  - the daily routines are similar and therefore rarely surprising things come to light (in the morning HRV is usually good, stress decreases it, eating decreases it, during sports it is decreased, relaxation exercises increase it, sleep increases it).