With the so-called heart rate variability, it is possible in the broadest sense to make the current stress status visible. It represents a measure of the degree of relaxation of the heart and allows conclusions to be drawn about the state of the autonomic nervous system. By combining the simple measurement with relaxation and breathing exercises, you can get direct feedback on changes in the nervous system.
What is heart rate variability?
To explain the term heart rate variability, we must first take a close look at the role of the autonomic nervous system. Also known as the autonomous nervous system, it essentially controls the organ functions – i.e. processes that humans cannot control at will (for example, the heartbeat). It is composed of the parasympathetic and the sympathetic nervous system. They work as an opponent: while the parasympathetic nervous system is responsible for all functions at rest, the sympathetic nervous system regulates active physical and mental performance. In general, the pulsing reflects the interaction of both parts. 1 The following example shows you what tasks they are doing:
An example of the control of the autonomic nervous system:
Suppose a pedestrian crosses the street and a car approaches faster than expected. The person is in a dangerous situation – the body has to react quickly. To ensure this, the cardiac output increases (controlled by the sympathetic nervous system). The stroke frequency, as well as the blood pressure increase and more oxygen-rich blood, can flow through the organism, so that the muscles are well supplied with blood and thus generate the necessary force to “escape”. The other way around, the performance also goes down again (triggered by the parasympathetic nervous system) as soon as the person relaxes. As a rule, such actions cannot be consciously controlled. The autonomic nervous system takes over the task.
So that the heart also reacts to signals from the autonomic nervous system, it itself has a network of nerves: it continuously registers external and internal stimuli such as dangerous situations, blood pressure and the state of excitement and responds to these impulses by adjusting the heartbeat.
So the intervals between the individual heartbeats change. Doctors refer to this as pulse rate variability (HRV). It can say the following:
- People with a limited heartbeat are quickly overwhelmed by external events and perceive them as stress. With them, the heart rate hardly changes even with external influences. This can lead to heart disease, depression, and other health disorders in the long term.
- A large heart rate variability, in turn, indicates a higher resilience. Affected people do not feel stressed as often, which results in a more stable state of health.
The measurement of the pulsing is thus a possibility to make the adaptability of the heartbeat to the constantly changing challenges visible. At the same time, it can be a reference point for the adaptability of the entire organism to external and internal stimuli.
How is HRV measured?
The HRV measurement takes place with common EKG (electrocardiogram) devices in doctor’s offices or with mobile devices for long-term measurement. If you are not a doctor and want to operate an ekg machine then visit https://www.exploremedicalcareers.com/ekg-technician/ to know more about it. Patients usually wear them overnight and return them to the practice the next day for evaluation. Heart rate monitor apps also show you the overall status of your health, including HRV, stress level, blood pressure, etc.
Strictly speaking, the doctor analyzes the distance between the so-called R-waves of the ECG and their variance (deviation). It is also known as the beat-to-beat interval. The beat-to-beat interval arises because the heart does not always beat the same, but adapts to external conditions. A precise analysis of the deviation is usually carried out using computer-aided programs.
Heart rate and breathing
Measuring the rate at which the heart beats is useful in a calm state. The heartbeat also adapts while breathing. The heart beats faster when you inhale and slower when you exhale. The breath-dependent variability should be large since the heart generally beats more slowly when at rest. If you only make a small movement, for example when scratching the head, it must increase the frequency. After the activity, however, it immediately goes back to sleep and beats more slowly. The variance, i.e. the HRV, is therefore large. The heart adapts well to current circumstances.
It is now also possible to gain insight into your own pulsation via smartphone and special apps, such as Welltory. The measurement takes place via a vital monitor – a device that is placed under the chest. It then forwards the data to the mobile phone, where it is precisely analyzed and presented understandably by the rescuetime app. Besides, such a heart rate measuring device also facilitates the user by providing a meditation tracker.
Besides, cell phone cameras can carry out an HRV measurement within milliseconds via brightness changes on the finger. Here, too, apps that you download to your smartphone evaluate the data. Apple health blood pressure monitor helps during the analysis, you need to put your finger on the camera and the flash. It detects the blood flow in the small vessels of the fingertip and uses the pulse variability to reflect the current stress level. Moreover, it has become so trendy to check blood pressure with iPhone and pulse oximeter app.
After the measurement: HRV values in detail
After measuring the heart rate variability, the device may spit out different values. These include:
- SDNN (Standard Deviation of the NN Interval): The value indicates how much the NN intervals deviate on average from the average. For example, a result of “68 milliseconds” is possible here. This means that a heartbeat is on average 68 milliseconds faster or slower than the previous one. The following applies: the higher the value, the better your heart variability, i.e. the adaptation of your heartbeat to changes.
- RMSSD (Root Mean Square of Successive Differences): This information gives you information about part of the autonomic nervous system, the parasympathetic nervous system. It shows how one heartbeat changes compared to the next and how capable the body is to recover. The following applies: larger values are better than smaller ones.
In order to obtain more details about the HRV, further measured values play a role. In addition to the time-based data listed, there are frequency-based parameters. They show the activity of the parasympathetic and sympathetic nerves. 4th
The doctor or the programs for the smartphone usually show you a summary of the values and provide information about your stress or regeneration status. Influencing variables such as age, gender, or the level of training are also taken into account in the calculation. 5
Heart rate variability and heart failure
Measuring heart rate variability can also provide clues about heart health. For example, there are diseases that lower HRV:
- Heart failure
- CHD (coronary artery disease)
- Diabetes mellitus
- Hyperthyroidism and hypothyroidism
After a heart attack, doctors sometimes use HRV measurements to conclude the risk of sudden cardiac death. 6th
Patients with left heart failure usually have a decreased HRV. However, it has been shown that sport and exercise enable an improvement in pulse rate. 7 Training is possible in different ways. Whether cycling, Nordic walking, or swimming: cardiac exercise should have priority in heart failure.
Biofeedback in heart failure
For many people, it is difficult to sense whether they are really relaxed or under stress. To get to know your own body better again and to find out what state it is in, you can use a pulse biofeedback devise.
With the help of biofeedback, it is possible to visualize changes in the nervous system that cannot be directly perceived by the senses. You can then have a positive effect on your nervous system through breathing or relaxation exercises. The so-called cardiac breathing has proven to be particularly effective: Imagine breathing in and out slowly and deeply through the heart instead of through your mouth and nose.
By making the achieved change in the heart rate variability visible, a permanent improvement in the body’s own regulation can gradually be achieved. The direct feedback of the biofeedback system enables stressed people to learn to relax through heart breathing or visualization exercises and to achieve a higher heartbeat.
Before you begin with this relaxation technique, you should do your research and understand HRV well. The best thing to do is to talk to your doctor or caregiver about it; they are sure to have a few valuable tips or contact points for you. Because especially at the beginning it is advisable to be shown the exercises and techniques exactly and to be accompanied during the first exercise.
If you are thinking about biofeedback in heart failure, it is important to consult a cardiologist.