As an active athlete or someone interested in health, one hears more and more often about the so-called heart rate variability. 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 (the 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 reality, however, the exact opposite is the case - but why?
Every human being has a multitude of sensors in his or her body that provide important feedback for controlling the heart in order to supply the entire body with blood in an optimal way. The vegetative nervous system then influences the heartbeat in its sequence. If this influence works 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 stressed.
You want more detailed information? Have a look at our webinar on the basics of heart rate variability: https://www.youtube.com/watch?v=ZAq5VdPkSt0 (only in German)
History of the HRV
The first documented use of heart rate variability dates back to the Chinese physician Wang Shu-ho in the 3rd century AD, who recognized even then that a very regular heartbeat is evidence of poor health. He recognized: "If the heartbeat is as regular as the woodpecker's knocking or the trickling of the rain on the roof, the patient will die within 4 days". At that time, the sensitive intuition of an experienced physician was necessary to recognize this condition. Today, 1700 years later, there are extremely accurate HRV measurement devices.
Fields of application of heart rate variability
HRV is primarily used in two areas: sports and health:
Training according to HRV
To adjust your training to your heart rate variability it is necessary to measure it at least twice a day. It is almost mandatory to use a HRV meter that calibrates to your body. HRV values are strongly dependent on age and person. Only with a device with calibration 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 recovery sessions to intensive intervals to strenuous strength training. If your HRV is low, you should do little or no training, depending on how low it is. Good apps show you this in an understandable way.
Recognizing overtraining through HRV - is that possible?
Yes, this is possible - if you perform at least one measurement every day. You can recognize overtraining by regeneration values that do not recover. Good HRV apps will show you this - here is an example from the Vitalmonitor portal:
Overtraining from mid October. The solution: more recovery time or less stress
HRV in the health sector
HRV as a stress indicator
In health management, heart rate variability is used to measure stress levels. Mostly this is also done with the help of a calibration phase, because the stress resistance of different people is very different. Good HRV apps use a mixture of the heart rate variability itself and a breathing exercise. This determines how long it takes the organism to adapt the heartbeat to the breathing pattern (the faster and stronger the coupling of the heartbeat to deep breathing works, the more recovered the organism is).
BioAge as a measure of lifestyle
Another frequently occurring value is the BioAge. It tells you how good your own HRV values are in comparison with other people. The lower the heart rate variability, the higher the biological age. The essential thing is that you can lower BioAge through exercise, nutrition, recreation & time management (check out a blog article about lowering BioAge here).
Biofeedback is about measuring biological processes and thus "training" them at the same time. Essentially, it is the targeted learning of the activation of the parasympathetic nervous system (sympathetic and parasympathetic nervous systems are two antagonists in the body. The sympathetic nervous system can be compared to a gas pedal - the parasympathetic nervous system is the brake). Measurements are again taken with an HRV measuring device. The biofeedback exercises show:
- a graphic instruction how to breathe and then record how the HRV behaves or
- you can influence what happens on the screen through your own breathing
By measuring and giving feedback on your body functions via heart rate variability, you can learn to influence them. Through regular biofeedback exercises you can increase your HRV and strengthen your stress resistance.
Factors influencing HRV
The following factors lead to greater or lesser heart rate variability:
- healthy nutrition
- balanced life
- regular sport
- enough recovery time
- no or lack of exercise
- during and directly after physical exertion
Improvement of heart rate variability
After describing which factors influence HRV it is relatively easy to improve heart rate variability. The possibilities are divided into 4 main groups:
- movement / sport: Whether movement or sport depends on the starting position. Overweight people should, for example, start with exercise or light swimming training to avoid damaging the joints. For all (hobby) athletes: Attention an intensive endurance or strength unit increases a possible stress load (during intensive load the same hormones are released as during stress). This can also disturb sleep.
- diet: Even with a healthy, balanced diet, an improvement in HRV is possible. The following measures promise rapid improvement:
- eat well before going to bed
- 5 times daily fruit and vegetables
- replace juices with water (juices often contain large amounts of sugar)
- abstain from alcohol
- pay attention to the ingredients of the food
- recovery: sleep makes up the majority of human recovery. Important factors here are the time of falling asleep, the length and depth of sleep and the work on the computer (smartphone, tablet, TV, laptop) before going to bed. Recovery stimuli can also be provided during the day through relaxation exercises. Examples of this would be yoga, autogenic training or biofeedback exercises etc.
- time management: If you learn to use time in the best possible way, you can also improve heart rate variability. It is important to clearly distinguish between free time and working time, to fix the workload clearly, to avoid multitasking if possible and to structure and prioritize work. This reduces stress and allows better use of recovery time.
Which HRV value is good?
This depends on several factors. Basically, the heart rate variability decreases with age. How this looks like is shown in the following diagram:
However, as described above, one's own HRV can be strongly influenced by lifestyle. How this can look like is shown in the following graphic:
The BioAge always indicates how good your own HRV values are for the age average. If the biological age is higher than the actual age, then you have worse heart rate variability values than usual for the age. It is the same the other way around.
What devices are available to measure HRV?
To measure heart rate variability, there are basically several different ways to measure heart rate variability, with different advantages and disadvantages:
This class of devices usually has a built-in ECG and thus a high accuracy. Stand-alone devices are usually 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 has to be performed and interpreted by a partner. Furthermore, a single measurement has little significance, since it depends very much on the daily condition.
Portable devices with pulse sensor
These devices have the advantage that they are usually cheaper than other HRV measuring devices. On the other hand, without ECG they are less accurate and the measurement cannot be verified (in ECG errors or extrasystoles can be detected - without ECG this is not possible). In this class of devices there are 2 subcategories::
- Devices that send the results directly to an app These HRV measurement devices have the advantage that results are available immediately after a measurement. In addition, proprietary smartphones and tablets are usually used as evaluation devices, so that additional hardware costs are eliminated. The corresponding apps clearly present the evaluation. Better devices (like the FLOW HRV) are calibrated by regular morning measurements on the own body and therefore offer a higher accuracy and better evaluations.
- Devices that record data and are later evaluated: The recording is usually done over 24 hours. One receives a device including an explanation from a partner and starts the measurement the next morning. The advantage here is that a whole day is recorded. The disadvantages are that
- o a partner is necessary for the evaluation & explanation
- o the statements depend on the state of the day
- o Daily routines are similar and therefore seldom surprising (HRV is usually good in the morning, stress reduces it, eating reduces it, during exercise it is reduced, relaxation exercises increase it, sleep increases it)..
Portable devices with ECG
The use of an ECG is the most accurate way to measure heart rate variability. As before, there are again two classes of devices:
- Devices that send the results directly to an app: Many years of research and development are necessary to determine heart rate variability using a portable ECG device. Due to the professionalism with which they were developed, these devices almost always have a baseline formation (the heart rate variability meter is calibrated to your body via regular morning measurements) and the possibility to view your ECG during and/or after the measurement. The most prominent example is the Vital Monitor.
- Devices that record data and are later evaluated: an additional advantage compared to pulse sensors that record data is the additional accuracy. The disadvantages remain the same as above.
What are the costs for HRV measurement?
The costs are strongly related to the measuring device used. A one-time measurement (24h HRV) with a supervisor will cost about 150-300€/measurement. If you buy your own HRV-measuring device with app, the costs will fall below 1€/measurement after one year of use. Additionally, you have the permanent monitoring of the HRV values and not only the picture of one day.