December 20

What is Heart Rate Variability and Why Does It Matter?


With a growing range of wearables measuring Heart Rate Variability (HRV), the common question is, "What is Heart Rate Variability?"  A wellness and performance measure that has grown from use by elite athletes to the man in the street.

HRV monitoring was a measure confined to elite sportspeople for years. But recently, it has become mainstream, with a growing group adding this to their arsenal of measures to monitor their overall health, including recovery, performance, stress, and sleep.

So, is HRV useful for the average person?

We all know about heart rate and know that it is the number of times our heart beats in a minute. We know it must be important. Doctors check it when we visit them. Nurses monitor it when we are in the hospital.

We know that excitement, or exercise, makes our heartbeat faster. Conversely, it beats slower when we are resting and even slower when we are sleeping.

What is Heart Rate Variability?

But few of us have heard about Heart Rate Variability.

So, what is it, and more importantly — why does it matter?

How is this variability a gauge of our health and well-being?

While you may think that if your heart rate is sixty beats per minute, it's beating once every second. However, that’s incorrect!

The heart is not a metronome, ticking along like a clock. Although we are not aware, it is not beating in a perfect rhythm. There are tiny varying gaps between each beat. 

These differences reflect the balance between the sympathetic nervous system (fight and flight) and the parasympathetic system (rest and recovery).

Nervous System

CNS Stimuli

When your body gets an external stimulus, your nervous system processes it and transmits information to the brain and other body parts.

Human Nervous System

The nervous system has two main parts: 

  1. the central nervous system (CNS) made up of your brain and spinal cord
  2. the peripheral nervous system (PNS) comprises the nerves connecting the CNS to the rest of the body. 

After processing these inputs, your central nervous system (CNS) activates your nerve network to send messages throughout your body.

Peripheral Nervous System

The Peripheral Nervous System

The Peripheral Nervous System (PNS) also has two parts: 

  1. somatic nervous system, which guides your voluntary movements while
  2. the autonomic nervous system (ANS) works behind the scenes, regulating essential functions like heart rate, blood pressure, breathing, and digestion.

The Autonomic Nervous System

The ANS is the primal part of the nervous system. With two competing systems that drive the heart rate variability:

  1. the sympathetic nervous system, the fight-or-flight mechanism 
  2. the parasympathetic nervous system, the rest-and-relaxation response.

The brain is constantly processing inputs from these systems in an area of the brain called the hypothalamus. The hypothalamus then signals the body functions to either jump into action or take it easy and relax.

The conflicting responses of fight or flight, or rest and restore in the sympathetic and parasympathetic nervous systems, create the HRV.

Nervous System Summary

In summary, when the human body detects an external stimulus, the nervous system is crucial in transmitting information to the brain and other body parts.

The CNS and PNS work together to ensure the body respond appropriately to the stimulus.

The sympathetic nervous system and the parasympathetic are two important divisions of the PNS that control voluntary and involuntary functions, respectively. Working together to balance the “fight or flight” and “rest and recover” responses.

Why HRV is Important

HRV measures how “well” our heart thinks we are. Are we physically or mentally stressed or primed and ready for optimal performance?

Heart Rate Variability is an Indicator

HRV is an important indicator of both physical resiliency and behavioural adaptability.  It is your heart's indicator of your vitality or depletion. Reflecting one’s capacity to adapt to our life’s stresses and demands.

Measuring the levels of your emotional and physical tanks.

HRV has significant daily variations. It is also personal and, therefore, meaningless to compare to anyone else. 

To establish your HRV baseline you need to get an average HRV over some time, usually a month or more. This should be measured daily, preferably at the same time of the day with you in the same state of mind.

This average value is your HRV baseline.

It is important to note that the HRV baseline varies by age, sex, and training status. 

An optimal, age-related level of HRV is associated with good health. It indicates self-regulatory capacity and adaptability or resilience.

Every person’s HRV is different, so there is no point in comparing yours with others.

Like VO2 Max, HRV declines with age. Note that these Normal Values are averages, and your baseline is likely to differ. Also, HRV is far more complex than heart rate or blood pressure.

What is HRV by age

HRV by age - Sun Scientific

Once your baseline is set, you need to track your HRV against this baseline using average numbers to get helpful information. It is normal to notice daily and seasonal differences in your HRV.

Normal Heart Rate Variability for Adults

A standard HRV for adults could range anywhere from less than 20 to greater than 200 milliseconds. 

Note that single and random HRV measures are useless. Measuring at the same time every day is essential, for instance, first thing in the morning. Also, HRV amplitude is age-related. Younger people have a wider range of natural beat-to-beat variations than older people.

The amount of HRV can and often varies with specific emotional states. However, the heart’s rhythm pattern is the primary indicator of the emotional state. Studies have also found that changes in the heart rhythm pattern are independent of heart rate.

This means one can have a coherent or incoherent pattern at high or low heart rates. Thus, the rhythm is most directly related to emotional and physiological states rather than the heart rate.

The affect of stress on HRV?

Typically, system depletion does not occur over a brief period unless exposed to extreme trauma. In the absence of a clinical disorder such as diabetes, reduction in HRV tends to occur over months and years. 

The cumulative effect of emotional stress is a significant source of chronic depletion.

The ANS balance responds negatively to a poor night of sleep or a hectic drive to work. But positively to the exciting news of a family engagement or eating a delicious, healthy meal.

As life goes on, our body receives and manages all kinds of stimuli.

Excess lifestyle burdens, including stress, poor sleep, unhealthy diet, dysfunctional relationships, isolation or solitude, and lack of exercise, disrupt the balance. When this happens, the fight-or-flight response shifts into overdrive.

Levels of HRV.

If the system is more in the fight-or-flight mode, the variation between subsequent heartbeats tends to be lower. The difference between beats is generally higher if the system is more relaxed.

The observation may seem counterintuitive, but the larger the variability, the more “ready” the body is to operate at a high level. 


Low HRV, relative to one’s age, maybe a predictor of future health problems, including all causes of death for older people.

In addition, low levels of HRV can be a marker of a damaged emotional and psychological capacity.

High HRV

However, variability is not always that simple to interpret. People with a high HRV generally have better cardiovascular fitness and are more stress-resistant.

Higher HRV is not always better as it can also result from disease or an abnormal physical condition. When certain heart conditions elevate HRV measurements, this can increase the risk of death, particularly among the elderly. These elevated levels can be explained by examining an electrocardiogram (ECG).

HRV can provide personal feedback about your lifestyle. It can help motivate people to take steps toward a healthier life.

Wellness and HRV

Widely considered one of the best metrics for physical fitness, Heart Rate Variability determines the body’s readiness to perform.

Lower relative HRV indicates that the body is under some stress. The difference between beats is generally higher when the system is ready for optimal performance.

With lifestyle changes, you can see a connection to HRV changes. As you benefit from more mindfulness, meditation, sleep, and especially physical activity into your life.

For those who love data and numbers, this could be a way to track how your nervous system is reacting. Reacting to the environment and your emotions, thoughts, and feelings.

Ways to measure HRV

The gold standard is to analyse a long electrocardiogram (ECG) strip done in the doctor’s office.

Commercially available HRV wearables (including Apple watch and Whoop) offer a non-invasive way to signal HRV.

The accuracy of these methods is still questionable, but the technology is fast improving. With the current options, chest strap monitors provide a more accurate measure of HRV than wrist devices.

Measuring the patterns in the Heart Rhythm

The most common HRV measurement involves measuring the variation over a given period. Although the amount of HRV is a crucial factor to measure, the rhythms and patterns in the HRV are more reflective of emotional states.

So, when looking at HRV, it’s possible to assess;

  1. how much variability is occurring (the amplitude of the wave) and
  2. the pattern of the heart rhythm (coherent or incoherent).

Your heart rhythm patterns reflect your emotions. When stressed or expressing negative emotions (fear, anger, hate, frustration), heart rhythm patterns are chaotic and look like a dangerous mountain with uneven jagged peaks.

Scientists call this pattern an “incoherent heart rhythm pattern”. You may have noticed that when you’re stressed, your creative thinking is impaired, you have trouble sleeping, and your immune system gets disturbed.

However, when expressing positive emotions like love, joy, gratitude, compassion, etc., you create a state of coherence (“coherent heart rhythm pattern”).

Your heart rhythm patterns look smooth, ordered and stable like a smoothe, harmonious set of waves. It helps your body’s systems synchronise and work better. It enhances your ability to think clearly, learn, remember, reason and make optimal decisions (peak performance).

HRV and Biofeedback

There has been substantial support for heart rate variability biofeedback (HRVB) as a treatment for various disorders and performance enhancement (Gevirtz, 2013).

These disorders vary from asthma, COPD, IBS, fibromyalgia, cardiac rehabilitation, hypertension, chronic muscle pain, depression, anxiety, PTSD to insomnia.

HRVB is also known as respiratory sinus arrhythmia (RSA) biofeedback or resonance frequency feedback (RFF). The procedure consists of feeding back beat by beat heart rate data during slow breathing manoeuvres. The participant tries to maximise RSA, create a coherent curve of peaks and valleys, and match RSA to heart rate patterns.

RSA is the heart pattern that occurs when heart rate increases during inhalation and decreases during exhalation.

In Conclusion

In general, a high HRV represents a robust physical and mental state and the converse for a low HRV.

But if you use HRV as a health indicator, do not get too confident if you have a high HRV or too concerned if your HRV is low. Think of HRV as an objective way to tap into how your body and mind responds to your daily experiences.

Latest generation wearable devices make applying and correlating measures to physical and emotional wellbeing look simple. This assumption is an oversimplification as many factors influence the results’ levels and interpretation.

There are questions about the accuracy, reliability and usefulness of tracking HRV. Although HRV has been linked to physical fitness, the correlation between changes in HRV and how the autonomic nervous system functions needs more research.

HRV has gained widespread acceptance as a clinical tool for evaluating cardiac autonomic changes in patients (Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996). Thus despite its limitations, HRV has proven to be an essential tool for identifying patients at risk for adverse cardiovascular events.

Performance athletes

Performance athletes use heart rate and HRV data to indicate how well they are coping with a specific training program or phase. Whether it has the desired results and whether there is increased fatigue. It can be effectively used as a helpful indicator to assess load on a specific training day.

Patterns and longer-term trends are essential. By performing trends analysis, we can better understand the big picture. Observe how different training phases and loads affect our physiology beyond the acute day to day changes in HRV.

HRV data can be an additional aid for a user or coach in conjunction with other non-autonomic (e.g., muscular fatigue) and subjective (e.g., stress, sleep) parameters.

Biofeedback can significantly increase HRV through using breathing techniques to synchronise the heart rate and create a coherent HRV pattern.

HRV is a helpful tool for anyone wanting to have a measurable basis for their wellbeing and fitness. It has a growing following and will grow in importance as a lifestyle accessory with improvements in technology and research.


Apollo Neuro, Apple Watch, biofeedback, heart rate variability, HRV Garmin, HRV polar, HRV Suunto, Whoop

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