The concept of Heart Rate Variability (HRV) has become trendy. A wellness and performance measure that has grown in interest as it has become accessible to more people. With a growing range of wearables now providing this measurement to zealous health and wellness followers.
So what is this trend all about?
We know our heart rate is the number of times our heartbeats 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 heart beat faster. And that it beats slower when we are resting and even slower when we are sleeping.
But few of us have heard about HRV or Heart Rate Variability,
So what is it, and more importantly — why does it matter?
For many years HRV monitoring was a vital measure confined to doctors and their ECGs and elite sportspeople. But recently, it has become more mainstream with a growing population of people interested in monitoring their overall health, including recovery, performance and sleep.
So how is heart rate variability a gauge of our health and wellbeing?
What is Heart Rate Variability?
You may think that if your heart rate is 60 beats per minute, it’s beating once every second. But that’s not correct!
The heart is not a metronome, ticking along like a clock. Although we are not aware of it, the heart isn’t beating in a perfect rhythm. The gaps between each beat vary by small amounts, and also the rhythms and patterns change.
There will be differences in time between any two beats within that minute. For example, there may be 0.9 seconds between two beats and 1.15 seconds between two others.
Your Central Nervous system (CNS), made up of your brain and spinal cord, controls these subtle difference. Then using your network of nerves — the Peripheral Nervous System (PNS), to send messages to the rest of your body.
The brain is constantly getting input messages from the senses.
After processing these inputs, it activates the nerve network (PNS), which relays information from your brain and spinal cord to your internal organs, arms, legs, fingers and toes.
The Peripheral Nervous System
The Peripheral Nervous System (PNS), contains your:
• Somatic nervous system, which guides your voluntary movements and the
• autonomic nervous system (ANS) which controls other activities without you thinking about them.
The ANS is the primitive part of the nervous system. It works behind the scenes, regulating essential functions like heart rate, blood pressure, breathing, and digestion.
The ANS has two competing systems that drive the Heart Rate Variability or HRV:
1. The sympathetic nervous system, the fight-or-flight mechanism and
2. the parasympathetic nervous systems, 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 creates the HRV.
Why HRV is Important
HRV is a measure of how “well” we are. In simple terms, are we physically or mentally stressed, or are we 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 reflects one’s capacity to adapt to life’s stress and environmental demands.
Personal HRV is the body’s indicator of vitality or depletion. Is your tank full or empty!
Typically system depletion does not occur over a short 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.
What Affects HRV?
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. If the system is more relaxed, the difference between beats is generally higher.
The observation may seem counterintuitive, but the larger the variability, the more “ready” the body is to operate at a high level.
HRV levels are age-related. Also, note that HRV is a lot more complex than heart rate or blood pressure.
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. You need to establish a baseline and 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.
Low HRV, relative to one’s age, is a strong 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.
However, variability is not always that simple to interpret. People with a high HRV generally have better cardiovascular fitness and are more resilient to stress.
But higher HRV is not always better since 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. The elevated levels are clarified by closely examining an electrocardiogram (ECG) to explain the high levels.
HRV can provide personal feedback about your lifestyle. It can help motivate taking steps toward a healthier life.
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. Not only to the environment but also your emotions, thoughts, and feelings.
Physical Fitness 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. When the system is ready for optimal performance, the difference between beats is generally higher.
The gold standard is to analyse a long strip of an electrocardiogram (ECG) done in the doctor’s office.
HRV wearables offer a non-invasive way to signal autonomic nervous system imbalances.
A growing number of companies have launched apps and wearable heart rate monitors that do something similar. The accuracy of these methods is still questionable, but the technology is 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 measurement of HRV involves measuring the amount of 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’re creating 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).
A standard HRV for adults could range anywhere from less than 20 to greater than 200 milliseconds. The best way to know your average HRV level is to use a wearable unit and measure the HRV at a set time. Within a few weeks, this will establish your baseline.
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. But 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 that 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.
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 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 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.