How Biofeedback Can Help Defeat Chronic Pain

Weaning patients off opioids and ending pain management visits thanks to cardiorespiratory training.

“The longer you have pain, the better your spinal cord gets at producing danger messages to the brain, even if there is no danger in the tissue”: Dr. Lorimer Moseley, a pain scientist at the University of South Australia, outlines how our brain and nervous system “learn” to keep producing pain. This statement offers hope – because we can also teach them to stop doing so.

Chronic pain is one of the most common reasons why adults seek medical care. Linked to numerous physical and mental conditions, it contributes to high healthcare costs and a decrease in productivity. Studies estimate that the prevalence of chronic pain in the U.S., as an example, ranges from 11 to 40% of the population. In 2016, an estimated 20.4% of U.S. adults had chronic pain; and 8% of U.S. adults suffered from high-impact chronic pain, defined as lasting three months or longer and accompanied by at least one major activity restriction. Authors of a recent case report propose that biofeedback can modulate heart rate variability (HRV) whole-health biomarkers by inducing cardiorespiratory efficiency. This helps to reduce unremitting hyperarousal as a cause for chronic pain, assess for opioid risk behavior, as well as improve overall outcomes.

Measuring pain 

The Pain Catastrophizing Scale (PCS), developed by Chaves and Brown in 1978, consists of 13 items rated on a 5-point scale. Participants are instructed to indicate the degree to which they have specific thoughts and feelings when experiencing pain. PCS assesses the extent of catastrophic thinking due to low back pain according to the key factors of rumination, magnification, and helplessness. Out of these, rumination is most highly correlated with pain outcomes. In this context, a recent case review demonstrates a bidirectional relationship between hyperarousal and pain linked to intrusive thoughts and catastrophizing.

In order to minimize catastrophic thinking, clinicians may work with patients to disengage attention toward pain symptoms. Persistent and inflexible sympathetic dominance appears to play a key role in relieving chronic pain; it can be measured by the variation in time between each heartbeat (HRV). Greater variability indicates greater ability of the autonomic nervous system to regulate itself. 

The case report by Raouf Gharbo et al., referred to above, looks to untangle the relationship between chronic pain and hyperarousal. By disengaging fear ruminations using heart rate variability biofeedback (HRVB), this framework has the potential to reverse the negative effects of helplessness as measured by PCS. This case presents an elderly female with a complex medical history who had suffered from daily axial low back pain for over five years, worsened by physical activity but temporarily ameliorated by opioids. The patient accepted the offer for a program centered on physiological grounding of fear ruminations with regular HRVB practice – a non-invasive therapy training aiming at increasing heart rate oscillations through real-time feedback and slow breathing training. 

The benefits of HRVB

HRVB training has been shown to improve HRV coherence (HRV-c), restore autonomic health, and reduce the severity of symptoms. With cyclical diaphragmatic breathing, HRV-c is achieved when cardiac beat-to-beat intervals increase and decrease in synchrony with respiration, and shift into a smooth sinusoidal rhythm. High HRV-c has been associated with improved mood, cognition, and executive functions. Raouf Gharbo et al., who also run a randomized controlled trial studying HRVB for chronic pain in veterans, describe the positive effects of HRVB training on their patient. Her skills of inducing and maintaining cardiorespiratory synchronization improved and persisted, she was weaned off opioids, and did not require any more pain management visits. These results underline that HRVB can enhance quality of life and reduce healthcare costs.

Today, patients can use their smartphones for managing chronic pain (e.g. Caspar Health, Kaia Health). Smartphones also enable HRV measurement, supporting patients who opt for breathing exercises to provide a simple and cost-effective way to take control of their body functions. The fight against chronic pain can be won, as Dr. Moseley suggested. 

Seasonal Affective Disorders: How to Fight It With Breathing Exercise

Breathing exercises as a treatment for seasonal affective disorders

Here’s how to deal with the seasonal mental health exacerbation

Long nights, dark days, and chilling temperatures: to quite a few of us, winter comes with major challenges for our mental health. For an estimated five percent of adults in the United States, e.g., the mood changes that occur as the amount of natural sunlight decreases are severe enough to be diagnosed as seasonal affective disorders. And the COVID-19 pandemic has been adding its toll during the previous cold season and the current one in the northern hemisphere: authors of a study published in the Lancet note an increase of more than 129 million cases world-wide of major depression and anxiety disorders compared with pre-pandemic figures. They attribute this to the “combined effects of the spread of the virus, lockdowns, stay-at-home orders, decreased public transport, school and business closures, and decreased social interactions, among other factors.” However, there are effective methods to increase mental health resilience.

Researchers describe seasonal affective disorders (SAD) as a “recurrent major depressive disorder with a seasonal pattern, usually beginning in fall (autumn) and continuing into winter months”. SAD disrupt the body’s internal clock and produce chemical changes in the brain; a sad mood and low energy are key symptoms of the condition. Risk groups include females, and are younger; they live “far from the equator”, and have family histories of depression, bipolar disorder, or SAD. Screening instruments include the Seasonal Pattern Assessment Questionnaire (SPAQ).

Some experts differentiate S-SAD, commonly seen as a subcategory and termed the “winter blues”, from “genuine SAD”. They claim SAD patients need to have experienced symptoms – such as feeling constantly tired, spending longer times in bed, increased appetite, lack of motivation, and disturbed sleep – consecutively for two years. Isabella Lovett counts among the proponents who state that the value of exercise in combating any form of stress, anxiety or depression – including SAD – is beyond doubt. Intense cardio and strength classes should be combined with mindfulness-based exercises and activities such as yoga and meditation.

According to researchers from Carnegie Mellon, for example, just 25 minutes of mindfulness meditation can significantly alleviate stress. For a study, 66 healthy individuals aged 18-30 years participated in a three-day experiment. Some participants went through a brief mindfulness meditation training program; for 25 minutes for three consecutive days, the individuals were given breathing exercises to help them monitor their breath and pay attention to their experiences. A second group completed a matched three-day cognitive training program. As a result, the first group reported reduced stress perceptions of speech and math tasks both groups were given to do, indicating that the mindfulness meditation fostered psychological stress resilience. More interestingly, on the biological side, the mindfulness meditation participants showed greater cortisol reactivity which, researchers assume, may be reduced over longer-term activities. In another example, Adam Borland, PsyD, a psychologist at the Cleveland Clinic, suggests taking ten minutes every morning for deep breathing and stretching to counter SAD.

Experts predict that during this northern winter, with COVID-19 continuing to upend our lives, SAD may become even more prevalent. Persons affected should seek counseling; to monitor effects of therapy, and for self-management in the context of building resilience, modern technology comes into play.

Patients can use their smartphones for measuring heart rate variability (HRV). As an important measure of health and wellbeing, HRV is significantly impacted by mood and mental health, and is increasingly being used as a measure of outcome in psychotherapy studies. To combine this biofeedback data with, e.g. breathing exercises provides a simple and cost-effective way to take control of body functions.

The battle against SAD is on. Let’s reduce the burden on our mental health with breathing exercises, managed through biofeedback.

How HRV Biofeedback Helps Combat Cardiovascular Diseases

Your heart plays a crucial role in your body. It is a muscle in the center of your circulation system which pumps blood around your body with every beat. This blood sends oxygen and nutrients to all parts of your body, and carries away unwanted carbon dioxide and waste products. Any impairments can lead to cardiovascular diseases.

Conditions of the heart and the circulation system – also called cardiovascular diseases (CVDs) – are a group of disorders which includes, in particular, coronary heart disease, cerebrovascular disease, and rheumatic heart disease. They are the leading cause of death globally. According to the World Health Organization (WHO), they cause an estimated 17.9 million deaths each year. More than four out of five CVD deaths are due to heart attacks and strokes, and one third of these deaths occur in people under 70 years of age. Most important behavioral risk factors are an unhealthy diet, physical inactivity, tobacco use, and harmful use of alcohol. Effects show up in individuals as raised blood pressure, raised blood glucose, raised blood lipids, and overweight and obesity.

The cardiovascular and the respiratory system exist in close vicinity to each other. Breathing directly affects the cardiovascular system. In turn, one of the main symptoms of congestive heart failure is shortness of breath. Cardiopulmonary exercise is one of the best things an individual can do to promote cardiovascular health: The pressure generated by breathing and expanding the lungs influences the volumes and pressures in the chambers of the heart and blood vessels. These changes stimulate sensory nerves that influence the autonomic nervous system (ANS) and the rate and depth of breathing. The pattern generators in the brainstem that drive and regulate heart rate, blood pressure, and breathing are also closely aligned. With exercise, a “central command” from higher brain centers accelerates the activity of both systems, and sends feed‐forward signals to the brain stem in preparation for the increased metabolic demands of exercise.

Where heart rate variability comes in

The analysis of fluctuation in intervals between heartbeats provides important information related to the autonomic modulation of heart rate variability (HRV). 

HRV parameters are considered predictors of morbidity and mortality, and researchers have pointed towards a close relationship between cardiovascular fitness and HRV. While HRV is often impaired in patients with cardiovascular and metabolic diseases, researchers found this relationship to be more pronounced in patients with cardiovascular and metabolic diseases and in aging. This became manifest, in particular, in individuals whose cardiovascular fitness and HRV were below the predicted values for the respective age and gender. Women in reproductive age as well as age-matched men show distinct regulations in cardiac autonomic modulation; and aerobic exercise was one type of training which appeared to attenuate any autonomic impairments.

And in the Journal of the American Heart Association (JAHA), Craighead et al investigated the effect of high‐resistance inspiratory muscle strength training on blood pressure, endothelial function, and arterial stiffness in older adults with mildly elevated systolic blood pressure. For that age group, their double‐blind, randomized, sham‐controlled trial showed that this type of exercise can improve control of blood pressure as well as increase HRV. 

Modern technology enables patients to use their smartphones for measuring HRV and pulse rate. To combine this biofeedback data with, e.g. breathing exercises is a simple and cost-effective way to take control of body functions. Patients will typically conduct these trainings in a setting with professional support. In the case of CVD, training accompanied by HRV measurement can help to prevent cardiovascular issues, to detect developing conditions for early intervention, and to monitor effects of treatment.

Cancer vs Biofeedback: Exercise for Stress Management and Resilience

Now patients can take control of a key risk factor for tumor progression with HRVB Exercise

Our contemporary lifestyles are particularly inducive of stress-related disorders. For oncology patients, this becomes even more of an issue: when diagnosed with cancer, many of them feel an increase in stress, and it can easily become chronic. And whereas there is no evidence that chronic stress causes cancer, it can make cancer spread faster. Effects of stress can be relevant both before, during, and after treatment. Tools are available which help patients cope.

In the context of cancer pathogenesis, there is growing evidence for biological and clinical implications of psychosocial and biobehavioral influences. Studies have shown the impact of chronic stress on metastasis: stress hormones stimulate angiogenesis, cell migration, and invasion, which leads to increased progression. Metastasis, when resistant to conventional therapy, is the major cause of cancer-related deaths.

Studies show impact of biofeedback training

Biofeedback (BF), including heart rate variability biofeedback (HRVB), appears to be a valuable tool in coping with stress. It can be used to control, and make subtle changes to, a variety of physical functions, such as heart rate. Biofeedback training (BFT) and heart rate variability biofeedback training (HRVBT) are based on three stages: initial conceptualization, skills acquisition and skill rehearsal, as well as transfer of treatment. In each of these phases, exercises aim at cognitive-behavior modification to induce change – patients, or clients, ought to become observers of, and actors on, their behavior and physiological responses.

BFT and HRVBT are effective: A study on BF-based interaction showed significant improvements in psychological test scores and salivary cortisol levels. In addition, results included increased grey matter (GM) volume in regions of the brain which are associated with stress response. According to the research team, the findings suggest that BFT affects the GM structures vulnerable to stress. HRVBT offers a useful tool for treating depressive symptoms in patients with psychological or medical diseases, according to another study published in Nature. This applies also to patients with cancer – depression affects up to 20%, and anxiety 10%.

While conventional BF methods provide information about the body by connecting individuals to electrical sensors, technology from kenkou enables patients to use their smartphones to measure pulse and heart rate variability (HRV). These measurements are accurate biomarkers for stress management. Combination of this data with BF exercises is a simple and cost-effective way to take control of body functions. Patients will typically conduct these trainings in a setting with professional support

Patients can take control

BFT helps to emancipate oncology patients in the context of key risk factors. This includes general stress as well as condition-induced stress after diagnosis and coping with treatment measures such as chemotherapy. Patients benefit from, e.g., slowed tumor progression and optimized monitoring of treatment.

Heart Rate Variability (HRV) – Your “Immunity Booster”

The link between the autonomic nervous system and immunity / How heart rate variability can be used to detect and prevent disease

Autumn and winter are peak seasons for infectious diseases. Our immune system is challenged by decreasing temperatures and wet weather, and the common cold, flu, and further threats to our health are gaining ground. More time spent inside, with other people around, adds to those risks. The current pandemic illustrates this seasonal trend, with various countries stepping up measures to control rising incidence. Let’s take a closer look at how we can take control of our immune status by measuring heart rate variability (HRV), and provide support to our physicians.

There is extensive communication between our immune system and our nervous system, experts explain. This includes the “hardwiring” of sympathetic and parasympathetic nerves to lymphoid organs – in particular red bone marrow, in which blood and immune cells are produced, and the thymus, where T-lymphocytes mature.

The sympathetic nervous system (SNS, which is responsible for “fight or flight”) and the parasympathetic nervous system (PNS, responsible for “rest and digest”) are the components of the autonomic nervous system (ANS). The ANS is critical in regulating processes required for maintaining physiological homeostasis and responding to acute stressors. Recently, researchers have been studying potential further functions of the ANS: it appears to play an essential role in regulating, integrating, and orchestrating processes between diverse physiological systems.

The modulators of immune activity

Neurotransmitters such as acetylcholine, norepinephrine, vasoactive intestinal peptide, substance P and histamine modulate immune activity. Neurotransmitters, often called the body’s chemical messengers, are molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles.

Central autonomic neural networks are informed of the peripheral immune status via neural and non-neural communicating pathways. While the immune system interacts directly within brain regions that regulate autonomic function, the autonomic nervous system innervates organs that contain immune cells, such as the spleen and bone marrow. Cytokines and other immune factors affect the level of activity and responsivity of discharges in sympathetic and parasympathetic nerves innervating diverse targets.

Heart rate variability (HRV) – biomarker of health

This is where heart rate variability (HRV) comes in. HRV biofeedback (HRVB) allows for measuring the autonomic function, with a host of applications for a variety of conditions.

In the context of immunity, the relation between HRV and inflammatory states has been extensively studied: for example, a meta-analysis of over 51 studies with a total of 2,238 patients demonstrated an inverse relationship between HRV and inflammation. While the precise mechanism of how the immune system and the ANS interact to impact the HRV may still have to be described, the common measure of HRV, the standard deviation of the interval between heartbeats (SDNN), is a viable indicator for monitoring the immune state. SDNN has been shown to correlate inversely with the nonspecific inflammatory marker C-reactive protein (CRP).

For measuring HRV, readily accessible, easy-to-use technology is available. A smartphone camera is the only device required. Its flash illuminates the fingertip, making changes in the blood vessels, which occur due to the natural heartbeat, visible for analysis. When blood is pumped through the vessels, they appear darker; blood being pumped out leads to lighter vessels. Based on these changes the heartbeat is analyzed, and the HRV is determined, providing the basis for computing further vital data indexes.

In the context of the immune system, this approach allows for the improved self-management of our health, and it provides significant support for physicians in diagnosing and monitoring their patients.

Heart Rate Variability Biofeedback (HRVB): Technique to Boost Wellbeing

How apps improve the management of chronic diseases, including diabetes

Noncommunicable chronic diseases, including cardiovascular disease, diabetes, and mental health conditions, were responsible for almost 70% of deaths worldwide in 2016. This is an estimate from The World Health Organization (WHO). The prevalence of these illnesses is increasing globally, leading to major social and economic consequences. The U.S. is a prime example: research by the American Action Forum (AAF) from September 2020 shows that chronic conditions in the country – already highly prevalent – are expected to rise over the next several decades among all age groups. The AAF calculates that, including indirect costs associated with lost economic productivity, the total cost of chronic disease in the United States reaches US-D 3.7 trillion each year, approximately 19.6 percent of the gross domestic product. Experts agree that action needs to be taken to reduce health care costs and improve patient wellbeing – and quality and effectiveness of disease management play a major role.

To better manage chronic diseases is key

Chronic diseases are generally linked to an imbalance of the autonomous nervous system (ANS). This results in sympathetic overstimulation and a lack of activity of the vagus nerve, a fundamental component of the parasympathetic branch of the ANS. This phenomenon, called dysautonomia, can both be a consequence of chronic disease as well as a key risk factor in its development. The study by Zalewski et al. emphasizes that ANS dysfunctions should be considered at each stage of the diagnostic and treatment processes. The identification of changes in vagal activity holds the key regarding the management, and detection, of chronic conditions.

heart rate variability biofeedback

Heart rate variability – biomarker of health

This is where heart rate variability (HRV) comes in. Heart rate variability biofeedback (HRVB) allows for the indexing of the autonomic function. Whereas high HRV reflects the ability of the cardiac system to adapt to intrinsic and extrinsic changes (e.g., stress), low HRV is an indicator of risk for cardiovascular morbidity and mortality. A systematic literature analysis by Shaffer et al. showed the feasibility of HRVB in chronic patients; significant positive effects were found in various patient profiles. Researchers concluded that heart rate variability biofeedback could be effective in managing patients with chronic conditions, including diabetes.

kenkou has developed a technology that enables vital data measurement (including HRVB) using just the smartphone camera. This readily accessible, easy-to-use technology serves to enhance treatment and detection of chronic conditions.

Heart Rate Variability (HRV): The Next Big Thing In Mental Health

Why is measuring mental well-being becoming critical and how can we make it as simple as checking temperature?

Loneliness, stress, anxiety, and depression: the COVID-19 pandemic has been severely impacting our lives. Health challenges affecting ourselves or our loved ones can cause strong emotions, and public health actions such as social distancing can make us feel isolated. The pandemic intensifies mental health challenges that were widespread already before the crisis.

Loneliness, as an example, is not just a painful experience we may go through. It is worse for us than smoking, more harmful than obesity, and it comes with a risk of premature mortality. In the UK, for example, the surging number of lonely people and how feeling alone harms us was presented by a pre-pandemic report by the Jo Cox Commission on Loneliness. According to Making Caring Common, a project of the Harvard Graduate School of Education, 36% of all Americans feel “serious loneliness.”

The World Health Organization raises the alarm: Approximately 280 million people in the world have depression. Survey conducted by The Centers for Disease Control and Prevention (CDC) among adults aged ≥18 years across the United States in June 2020 suggests that 40.9% of respondents reported at least one adverse mental or behavioral health condition, including symptoms of anxiety disorder or depressive disorder (30.9%). The waiting lists for psychotherapy are getting longer. “With anxiety and depression on the rise during the pandemic, it has been challenging for people to get the help they need” – writes The New York Times in a recently published article.

These examples illustrate the scope of the issue and the need to support therapy when qualified help is hard to find.

Untapped power of HRV

In light of this high incidence of risk factors and conditions and lack of professional staff to address for help, what can individuals do to find out if they are at risk? Whereas a panic attack may be easy to identify, the slow rise in blood pressure or inflammation is difficult to notice. In this context, heart rate variability (HRV) comes into play. It is a promising biomarker of mental health resilience (MHR).

MHR influences mental well-being and vulnerability to psychiatric disorders. Whereas conventional measurement of resilience is based on subjective reports, HRV can act as an objective biological, physiological biomarker. A study published in the Journal of Affective Disorders showed that HRV might indeed serve as a global index of an individual’s flexibility and adaptability to stressors.

body mind connection

Effective therapy is available, but simple methods of diagnosis are lacking

Cognitive Behavioral Therapy (CBT) is the most widely-used therapy for a wide variety of mental health disorders. Research has shown it to be effective in treating panic disorders, phobias, social anxiety disorder, and generalized anxiety disorder, among many other conditions. CBT is a “talking therapy” that can help individuals manage their problems by changing the way they think and behave. The therapy aims to help individuals deal with overwhelming problems in a more positive way by breaking them down into smaller parts. CBT is based on the concept that one’s thoughts, feelings, physical sensations, and actions are interconnected, and that negative thoughts and feelings can trap individuals in a vicious cycle.

However, a diagnosis is needed to begin CBT, and this is not always easily available. Accurate tracking of selected biomarkers including HRV can be a game-changer.

As a noninvasive and easily applicable biomarker of MHR in real-life contexts, HRV allows for accurate stress level measurements for CBT. It helps in tracking recovery by identifying the change in behavioral patterns and treatment progress over time. In addition, it serves as an index of cognitive and affective self-regulation. Whereas negative emotions are related to reduced HRV and incoherent heart rhythm patterns, cardiac coherence refers to a high amplitude sinus-like heart rhythm that is characterized by increased vagal activity. This is associated with a psychological state of positive emotion.

HRV biofeedback (HRVB) devices display heart rhythms in real-time. They can be used to teach patients to generate coherent oscillations in the heart rate. A combination of CBT and HRV biofeedback training can help reduce anxiety symptoms while increasing HRV and the ability to sustain cardiac coherence.

When properly applied, digital technologies may prove to be groundbreaking in addressing the problem of early diagnosis and treatment of selected mental illnesses.

Technology developed by kenkou for precision biofeedback

kenkou – a Berlin based startup founded in 2014 – is developing technologies that can revolutionize mobile health and vital-data measurement worldwide. Together with a team of data scientists, the company is exploring the power of HRV in mental health tracking.

mental health app and heart rate variability
Photo by cottonbro from Pexels

The science behind HRV: how does it work?

The time interval between the heartbeats of a healthy heart is constantly fluctuating. It indicates how well your body handles stress. Intervals over a given time period are referred to as HRV. A high HRV indicates that your body can cope well with stress, whereas a low HRV can be a symptom of fatigue, stress, or even illness. There are many values that can be used to measure HRV, including RMSSD and PNN50.

RMSSD (Root Mean Square of Successive Differences) shows how well an individual’s body is recovering from stress and reflects how well the parasympathetic nervous system can help it to regenerate and recover. A high level of stress relief is partly due to a high RMSSD.

PNN50 (correlated with Parasympathetic Nervous System activity) is the fraction of consecutive heartbeats with an interval greater than 50 milliseconds between them. A higher PNN50 value shows that an individual’s heart rate has drastically changed within a brief time period. For healthy individuals aged 25-74 years, the range is -3% to 43%.

Respiratory Sinus Arrhythmia (RSA) Amplitude, sometimes referred to as the HRV amplitude, is the change of heart rate believed to be caused by breathing. Kenkou measures it by breaking up measurements into sections that match the expected breathing interval of the user – ten seconds in length –, calculating the difference between the maximum and minimum heart rates and averaging the results found for each of the sections.

kenkou computes a spectrum of indexes. This includes the Tension Index: this heart rate index is determined by the heart rate variability and is an objective indication of how much stress and tension there is in the body. Recovery Ability is related to an individual’s relaxation ability; it is measured by the parasympathetic nervous system, which controls the body while at rest. The easier it is for the body to calm down, the higher its stress resilience.

How do we make vital signs checkup as simple as possible, accessible to everyone?

kenkou’s team has developed a technology that enables vital signs measurement (including HRV) using just the smartphone camera. Its flash illuminates the fingertip, making changes in the blood vessels, which occur due to the natural heartbeat, visible for analysis. For example, when blood is pumped through the vessels, they appear darker; blood being pumped out leads to lighter vessels. Based on these changes, the heartbeat is detected, the data is analyzed, and the HRV is determined, providing the basis for computing further vital data indexes.

Readily accessible, easy-to-use technology from kenkou enhances treatment of mental health challenges in the pandemic and beyond. The company’s software development kit (SDK) enables cardiovascular vital signs analysis through third-party applications in the digital health and well-being industry as well as for insurance and pharmaceutical companies.

Heart Health: Correlation Between Pulse Rate and Heart Diseases

Can we avoid cardiovascular disease by regular monitoring our heart rate variability? How can on-time regular HRV measuring help to detect CVDs?

Did you know that cardiovascular diseases, or CVDs, are the leading causes of death and morbidity in industrialized nations, accounting for 32% of all deaths? It is the unfortunate truth, that despite the major advancements in healthcare accessibility, technology and improved medical treatments over the last decades, the frequency of cardiovascular conditions as well as the associated mortality rates continue to increase. The risk of developing CVDs also rises with age, and patients who suffer from CVDs often require chronic or recurrent hospitalization and long-term medical treatment, with all the costs that this implies for the healthcare systems.

There is a strong link between heart health and heart rate variability (HRV), as well as the value of the latter as a direct indicator of autonomic nervous system (ANS) disbalance. Let us explain what each of these terms means. HRV represents the variability in the time intervals between successive heartbeats while ANS is responsible for key physiological functions in the body, including cardiovascular activity. It regulates heart contractions and heartbeat, as well as blood pressure, which explains its essential role in maintaining cardiovascular functioning and health.

The amount of currently available research on the relationship between CVD and unbalanced sympathetic-vagal outflow to the heart confirms the important influence of the ANS on cardiovascular health. HRV is an established marker of how both branches of ANS (sympathetic and parasympathetic) work. Tracking HRV levels can play a key role in understanding cardiovascular risk factors, as well as the onset of the cardiovascular disease itself.

Today, HRV is an acknowledged index for cardiovascular science and diagnostics. It has become a standard non-invasive metric for evaluating the autonomic nervous system, serving as a convenient and relatively cheap tool for ANS function assessment and tracking. This has led to an increase in the development of devices that can track HRV levels, like smartphone-integrated apps and tools, or wearable devices. Available to the vast population, such consumer tools can have an exceptional impact on HRV monitoring, cardiovascular disease diagnostics and care.

heart anatomy
Photo by jesse orrico on Unsplash

The correlation between HRV and CVD

HRV serves as an indicator of the activity levels of the sympathetic and the parasympathetic branches of the ANS, as well as of the way these two branches modulate together the heart activity. A high HRV is a sign that the heart is operating well, and that it adapts to various stressors quickly and efficiently. In contrast, a low HRV can be an indicator of reduced cardiovascular fitness and of too much stress, when the sympathetic nervous system is constantly activated. Dysfunction of the ANS plays a major role in the development and progression of cardiovascular diseases, including myocardial infarction, heart failure, and sudden cardiac death.

In normal conditions, HRV values are constantly fluctuating throughout the day, as they are highly dependent on the interaction between the two branches of the ANS – sympathetic and parasympathetic. When the body is under stress, the sympathetic branch promotes the release of stress hormones, putting the body in the “fight-or-flight” mode. On the other hand, the parasympathetic branch is activated during more relaxed and less stressful times, turning on the “rest-and-digest” mode. When the sympathetic branch is strongly activated HRV values are low. A low resting HRV can serve in certain cases also as an indicator of cardiovascular risk factors, along with others, such as unhealthy lifestyle habits (like a sedentary lifestyle) and additional health conditions (like diabetes).

It is already well known that patients who exhibit low HRV levels following a CVD-related event (e.g. heart attack) have a more difficult recovery process and higher mortality risk. Therefore, tracking HRV levels can help not only to detect the early onset of CVD but also serve as a prognostic factor for patients with ongoing or past CVD conditions.

From a preventive perspective, routine HRV monitoring is meaningful also for individuals who had no previous history of cardiovascular conditions. Research shows that individuals who show fewer fluctuations in the heart rate and exhibit enhanced HRV values are overall healthier. In these individuals, a sudden change in the HRV values can act as an immediate and direct indicator of declining health status.

In general, a low HRV usually means that the sympathetic branch of the ANS is dominating and preparing the heart and the body to take on more stress than normal, which makes the heart beat faster and with less variability.

However, in cases of strenuous exercise, a decreased HRV is not a bad sign, but only an indicator that the body is dealing with physical exertion. In this case, ANS signals to the heart that the focus should be turned to uttermost parts of the body rather than internal processes.

heart health

Impact of HRV metrics on CVD detection

HRV is one of the most informative indicators of risks linked to cardiovascular disease and therefore, received a lot of attention in the last couple of years. New methods for both tracking and analyzing HRV metrics are being developed to offer healthcare providers a convenient and easily accessible method of detecting and monitoring various health conditions. The final goal is to alleviate the burden on the healthcare system by bringing heart health tracking methods closer to actual patients and raising their awareness about CVD risk factors.

In the last decade, thanks to automated analysis methods, HRV has become a regular part of the routine examination of patients with cardiovascular risks and chronic cardiovascular disease. HRV represents a useful tool for documenting events in various clinical settings, and remarkably low HRV measurements have been clearly linked to the severity of CVD, additionally proving how strong HRV and CVD correlate.

HRV could therefore become a valuable tool for assessing the health of the general population, as well as offer a method for detecting risk factors for cardiovascular disease. Previous studies did prove that HRV measurements can be used to predict increased mortality risk in patients who suffered from a heart attack or heart failure. However, the research available today on the link between HRV, ANS and CVD is still partial, and requires further studies before tools for CVD risk factors can be derived and fully accepted.

heart rate measurement
Image by Apichit Yutithammanurak from Pixabay

Alternative ways to measure HRV

24h-long monitoring is considered to be the optimal length for reliably tracking the changes in HRV metrics. Usually, such long measurements are performed with special ECG devices. However, given the time that such monitoring duration requires, other approaches need to be considered and developed. Particularly, using a smartphone or another wearable device to measure HRV in shorter or selected intervals throughout the day. It is a desirable alternative that is much more convenient and economical and delivers long-term measurement benefits.

Furthermore, the onset of cardiovascular disease can be the result of a combination of various factors, which must always be taken into consideration. HRV, therefore, should not be treated as an exclusive indicator of heart-related health issues, but rather as a valuable addition and a convenient tool for monitoring the efficiency of cardiovascular regulation.

HRV metrics need to be smartly integrated with the existing tools for identifying, tracking, and quantifying risk factors of CVD. However, an overestimation of the HRV as a predictor for lifetime risk of CVD should be avoided. Nevertheless, in combination with regular and specific checkups with medical professionals, HRV has immense potential in helping the general population take better care of their health and build lifestyle habits that enhance both life expectancy and quality

Heart Rate Variability (HRV) Tracking: ECG vs PPG Technologies

Which is better for heart rate monitoring: ECG or PPG? How to measure heart rate variability in most accurately.

The heart is a complex organ. Apart from continuously pumping blood over an entire human lifespan, the heart provides valuable insights into the general state of different processes in the body. Monitoring the heart enables a wide range of mental, emotional, and physical health assessments, like stress management capability or the state of mental and cardiovascular health. Finding new ways to monitor the heart can help detect the early onset of cardiovascular disease, which shows the potential for preventive health. Heart rate variability (HRV) is the most valuable metric for assessing how the autonomic nervous system (ANS).

The contraction activity of the heart muscle relies on electrical impulses and is strongly regulated by the autonomic nervous system (ANS). The ANS controls many body functions through the interchangeable activity of its two branches: sympathetic and parasympathetic. Heart rate variability (HRV) assesses how the body’s capability to take on and manage stress. As a measuring unit of the variability between heart beats, HRV directly indicates how the ANS is functioning.

Modern technology and advancements in the field of medical devices offer new methodological possibilities for non-invasive HRV tracking. The most widely used sensor-based technologies are ECG (electrocardiography) and PPG (photoplethysmography). For those who are looking for the best HRV detection technology to include in apps for wearable devices, this article will outline the similarities and differences between the two, as well as point out the advantages and limitations each of these methods, bring to HRV measuring.

heart rate variability ECG

ECG for HRV recording

Short for electrocardiography, ECG measures the electrical activity of the heart over a period of time through electrodes that are attached to the skin. ECG essentially records the electrical activity of the heart muscle and how it is affected by different factors like the activity of the ANS. It records signals that happen far from the skin’s surface, which ECG electrodes capture instantly and accurately. This makes ECG a non-invasive method for measuring HRV and it is used as the reference standard diagnostic test by many healthcare providers who assess cardiac health. 

The result of an ECG reading is called an electrocardiogram, and its most relevant feature for analyzing HRV is called the QRS complex: a graphical hallmark of the heart’s periodic electrical and contractile activity. Algorithms use the time interval between successive R waves to measure the duration of a heartbeat and calculate HRV values, which make ECG a highly accurate, robust, and sensitive method of measuring HRV. This also means that a substantial reading can be accurately accomplished in a short time frame (e.g. < 5 minutes) as well as during a wider range of activities (e.g. a 24h ECG recorded during habitual daily movements).

PPG for HRV recording

PPG (short for photoplethysmography) is a very simple optical technique for measuring HRV. Unlike ECG, which uses electrodes, PPG applies light reflection to detect the blood volume changes in peripheral arteries which occur with each heartbeat. Recordings are usually measured on parts of the body where blood vessels are close to the skin, like fingertips or earlobes. The recorded pulse waveforms are the basis for measuring HRV through PPG.

Advantages and limitations

Readings obtained through the ECG method have proven to be more accurate and comprehensive than those obtained through PPG. This is mainly because ECG reads the electrical signals produced by the heart activity directly, while PPG provides a more indirect measurement, using light reflection to detect the pulsating activity of the heart. When it comes to ease and accuracy of measuring, PPG can be measured at several positions on the body and offers a wide range of measurement possibilities, while ECG requires more specific anatomical placement of electrodes on the body.

PPG measurements are influenced by the number and proximity of the blood vessels present on the placement spot, which makes the accuracy of PPG change according to the body position. The accuracy of PPG also depends on external factors, like the effect of ambience lighting and in some cases even motion factors. This means that PPG could become less accurate in measuring HRV during exercise and may require additional data processing steps to improve accuracy under challenging conditions.

ECG can produce accurate data faster and in a more direct way than PPG, as it includes electrical readings and does not require settling time. However, ECG also introduces several challenges related to the collection and interpretation of data, as it relies on a physician to be prescribed, performed, and interpreted. This greatly limits access to this tool for diagnosis, care, prevention, or general HRV tracking. An interesting finding is that comparing 5-minute readings from both methods indicated a very high degree of correlation between ECG and PPG as methods for measuring HRV.


ECG and PPG represent two different approaches to measuring HRV in a fast, convenient, and accurate manner. Studies show that PPG is a valuable tool for HRV measuring under ideal conditions and shows great potential in becoming a more practical alternative to ECG for HRV tracking and analyzing. Both methods for measuring HRV offer accessible tools for diagnosing how the ANS is functioning, which can further help early detection of certain conditions and provide insights into the overall health of the body.

Read more about HRV and HR:

What is HRV and how can it leverage digital health?

Heart Rate Variability (HRV) and Heart Rate (HR) Tracking

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Heart Rate Variability (HRV) and Heart Rate (HR) Tracking

What is the key difference between HRV and HR? How and when should we track and improve heart rate variability?

Recent developments in digital health have introduced various wearable devices and apps for acquiring vital biomarkers and obtaining advanced health metrics, ultimately transforming the way we measure data and use it to understand and improve our health. A metric that has recently received a lot of attention is called Heart Rate Variability (HRV), and owes its popularity to the ability to provide valuable, non-invasive insights into our health status and expand the potential of digital biofeedback.

Although often measured alongside the Heart Rate (HR), HRV is a metric that offers more detailed and accurate information than HR alone. To understand how these two vital measurements can be fully and unambiguously interpreted, this article will explain the similarities and differences between HR and HRV, as well as how they can be applied to health tracking and improvement.

What is Heart Rate and how to use it

Measuring HR means obtaining an average beat-per-minute (BPM) value, which tells us how fast the heart is beating. Easy to record and interpret, HR has perhaps been the most widely used metric in medicine for centuries. Most people show an average HR value of somewhere between 60 and 100 BPM in a rested state. Different HR readings can offer insights into the state of our cardiovascular system.

A low HR reading shows measures of < 60 BPM and usually indicates that the body is in a rest-and-digest state. Low HR is also normal in athletes or during sleep. It can also be a sign of a condition called “bradycardia”, which causes fatigue, dizziness etc. A higher HR reading shows measures of >100 BPM and usually means that the body is under physical or psychological strain. High HR is normal in some cases, like during exercise, or it can indicate a condition called “tachycardia”, which is associated with various symptoms and complications.

However, the heart rate is, per definition, a measurement that provides an average value and only shows how many times the heart beats in a minute. An average of 60 BPM could mean that the heart beats once every second, or that it alternates at a 0.6 seconds followed by a 1.4 seconds rate, or at any of the endless range of time intervals between successive beats. In summary, the heart does not beat to a regular pattern, but rather slows or fastens its pace to adapt to several physiological or pathological factors. HR measurements at any given time, therefore, provide limited information about human health or well-being. 

What is HRV and how to use it

heart rate

HRV represents the variability in the time intervals between successive heart beats. In contrast to the HR, the HRV takes into account what happens in each heartbeat. Such variability in the heart activity has its origins in the Autonomic Nervous System (ANS), which comprises two branches and regulates various automatic processes in the body, including digestion, heart rate, breathing, even sexual arousal. . Given its strong connection with the activity of the ANS, measuring HRV has a wide range of applicability. 

By helping us understand the current state of the autonomic nervous system and how well it is functioning, HRV provides insights into all the processes in the body that are equally controlled by ANS. This means that tracking HRV can help us understand the link between cardiovascular activity and the respiratory system, stress management, fitness and recovery, and other health related processes and functions inside the body.

A high HRV at rest usually indicates that the heart is operating well, and that it adapts to various stressors quickly and efficiently. On the other hand, a low HRV at rest can be an indicator of too much stress, a previous intense workout, or several other impaired processes in the body.

HRV therefore represents a metric that is more insightful, widely applicable, and valuable than simple HR recordings. However, quantifying the variability between successive heartbeats requires the calculation of complex scores from the HRV readings and more sophisticated tools for interpretation than simple HR readings.

Vital biomarkers collecting and interpreting

Recent advancements in technology have enabled smartphone apps and wearable devices to collect and interpret HRV metrics in a non-invasive, affordable, and convenient way. This makes HRV readings within everyone’s reach, easy to interpret and implement in your health management habits. HRV and HR have commonly been associated and are even mistakenly considered equivalents. Understanding the difference between HR and HRV and how they can be used is very important, as it can help you reach health related goals and establish better habits more efficiently.

When to measure HR

The best moment to measure HR at rest is in the morning, ideally in bed, after a good night’s sleep and before the first coffee. HR at rest provides basic insight into how well your heart is functioning, whether you exercised enough etc. Once you know your average HR at rest, it is indicative to track it during strenuous conditions (like during exercise), as it reveals how physical exertion affects your heart rate in real time. This type of tracking is a useful basic tool for training your heart and adjusting your routine to match the state of your cardiovascular system.

When to measure HRV

Interpreting HRV metrics offers insights into the way the ANS is functioning, which can help you understand the state of your overall health, as well as your body’s ability to manage stress and recover from physical exertion. However, that also means that HRV is a very sensitive metric and, therefore, some additional planning and interpretation are required when it comes to its measurement, especially when performed in short intervals.

While valid HR can be measured during an activity, HRV is more easily interpreted before and after a certain task or challenge, in more “controlled” conditions (e.g. without interference). For measuring the effect of meditation on stress recovery, it makes sense to compare HRV before and after that activity in absence of additional stressors or relaxants. 

The most important thing to keep in mind is that although HRV and HR are commonly considered to provide similar vital data, they are in fact very different from one another and should be measured individually. HR is a valuable tool for basic medicine and for interpreting the immediate effect of physical and psychological exertion, while HRV offers deeper insights into the functioning of the ANS and all the biological processes it regulates.

If you are interested in knowing more about HRV and uncovering the full potential it has for helping the body learn how to better manage stress, improve fitness, and even help improve mental health, visit our full collection of HRV related articles.

Read more about HRV and HR:

What is HRV and how can it leverage digital health?

If you have questions about how our SDK works, please contact our sales department here.