Heart Rate Variability

Heart rate variability (HRV) is an essential measure of your health. Tracking your HRV score can be a valuable tool to identify imbalances in your autonomic nervous system. The autonomic nervous system regulates various parts of your body, particularly your cardiovascular system, which includes blood pressure, heart rate, and more. In this article we will explore various aspects of HRV and discuss how a HRV assessment provides important insights into your overall health.

What is HRV?

HRV is a measurement. Not to be confused with a general heart rate measurement, which is simply the number of heart beats across one minute. HRV specifically measures the variations or changes in the length of time between each heartbeat, recorded over a defined period.

Our heart does not beat evenly, which means that the time that elapses between each heartbeat varies. A heart beating 60 times per minute will not usually beat precisely once per second. Instead, some beats are closer together and others are further apart.

HRV Scores

The results you get from having your HRV measurements is called a HRV score. This is the measurement and comparison of the time that lapses between heartbeats over the test period. A higher HRV score is better than a lower one as it can indicate a better level of recovery. We explain this in a little more detail below.

Please note: some medications and medical conditions can produce a higher HRV score.

What we are aiming for is a greater level of variability in a HRV score, as this reflects how well the autonomic nervous system is responding to stimulus from both the internal and external environment. This variability optimises our capacity to adapt to any stressors we encounter in life. Greater variability in your HRV score indicates a more resilient, responsive, and healthy nervous system. When a more consistent (less varied) HRV score is evident, this reflects an autonomic nervous system that is under stress and possibly not functioning at an optimal capacity.

Side note! Longer gaps between each heartbeat in your HRV score simply reflects a lower heart rate, not necessarily greater variability.

Biology

The sinoatrial node of the heart is a collection of cells called myocytes that spontaneously generate an electrical impulse to initiate the muscle contractions of the heart. The sinoatrial node is the ‘pace-maker’ of the heart.

These sinoatrial cells are influenced by the autonomic nervous system. The sympathetic nervous system increases the rate of electrical firings and in doing so increases the heart rate. The parasympathetic nervous system decreases the rate of electrical signals and consequently decreases the heart rate.

In essence, a predictable heart rate reflects a nervous system that is too stressed to influence the rate of electrical signals at the sinoatrial node. When this happens, the sinoatrial node goes into automatic pace-making mode. This will result in a low heart rate variability score.

Why Measure HRV?

Heart rate variability is strongly linked to the body’s independent regulatory systems and therefore is a measure of health. Optimal HRV indicates that the body is performing efficiently and has self-regulatory capability. It also shows that the body can adapt to external changes promptly and appropriately.

On the contrary, a reduced HRV score indicates a potential heart problem that may lead to a heart attack or congestive heart failure. A chronically low HRV scare is very serious. It reflects a nervous system that is not functioning well enough to keep the organism alive.

Regularly monitoring HRV can enable you to take timely action to avoid health complications and improve overall health.

How to Measure HRV

Access to a variety of technologies is available to measure HRV. This is a variety of consumer technologies currently available for the at-home HRV enthusiast, for example: chest straps, smart watches, smart straps, and rings. One of my at-home favourites is WHOOP. This wearable fitness and health coach measures multiple body vitals, such as respiratory rate, blood oxygen, resting heart rate, and skin temperature, to build a more comprehensive picture of an individual’s current health.

You may have also heard of more advanced technology that can be used to measure HRV, including pulse wave profile systems and electrocardiograms (ECG). These systems remain the most sensitive and accurate options. These technologies are significantly more advanced than general heart rate monitors as they can track electrical activity more precisely.

I use a pulse wave profiler tool with my patients at Silverback Chiropractic. It is a great metric to track patient progress throughout their care program.

HRV and The Nervous System

Whilst HRV is an indication of heart function, the heart takes its orders from the nervous system. Our autonomic nervous system is responsible for controlling various aspects of our physiology and consists of two branches. They are:

parasympathetic (deactivating), and
sympathetic (activating).

The Parasympathetic Nervous System

The parasympathetic nervous system controls bodily responses for rest, digestion, and self-healing. It produces a reduction in heart rate so when the body is in parasympathetic mode, the gaps between beats are (on average) longer.

The Sympathetic Nervous System

The sympathetic nervous system is activated by stress. This could be in form of emotional stress or physical stress like exercise. This produces an increase your heart rate and blood pressure.

Variations in our heart rate are determined by these two competing branches of sympathetic and parasympathetic, which are simultaneously sending signals to your heart. If the nervous system is balanced, the parasympathetic system tells your heart to beat more slowly, and the sympathetic system tells your heart to beat faster. This entire process causes fluctuations in your heart rate.

As mentioned earlier, a greater level of variability reflects the autonomic nervous system’s ability to respond to stimuli from both the internal and external environment. This ability of the body to respond to our environment optimizes our capacity to adapt to the immense variety of stress we encounter each day.

Consider it a nervous system tug-of-war. The sympathetic and parasympathetic systems will constantly push and pull at each other to adapt to the environment; consequently, creating a fluctuation of changes in the pattern of the heart rate as required. Isn’t the body amazing!?

In a tug-of-war that is out of balance (for example, when the sympathetic nervous system becomes too dominant) there is an increase of stimulation to the electrical firing at the sinoatrial node. This results in the heartbeat becoming more predictable and as such, creates smaller variations in heart rate. In this situation, a lower HRV score will be present.

Improve Your HRV

An optimal HRV level indicates that the parasympathetic and sympathetic nervous systems are operating appropriately, so your body is managing stress and heightening recovery. In contrast, a lower HRV can reflect a nervous system under too much stress or distress, predisposing or leading to anxiety and depression.

Here are some ways to improve your HRV:

1. Regular Exercise

Regular exercise is the most effective way of improving HRV. Develop an exercise habit of walking, jogging, cycling, team sports or group fitness classes. Physical activity improves heart function and improves your overall health.

2. Drink More Water

Staying hydrated is necessary because it affects the amount of blood in the body. The more fluid in your system, the easier it is for your blood to circulate throughout the body and supply essential nutrients and oxygen. It is recommended that you drink at least 6-8 glasses of water in a day for sufficient hydration. Don’t forget, if you are doing regular high-intensity training or sweating a lot, you will need even more water!

3. Consume Healthy Foods

Eating unhealthy and inflammatory foods will disrupt the function of the heart and will have detrimental effects on your overall health. Consuming a healthy diet, including good fats, adequate protein, and fresh fruits and vegetables will improve your circadian rhythm and nervous system health.

4. Get Enough Sleep

Getting at least 6-8 hours of sleep a day is necessary but it’s not just about getting enough sleep; you should aim to improve the quality of your sleep as well. One way to achieve this is by maintaining consistency in your sleep schedule. A consistent sleep schedule allows you to achieve more REM (rapid eye movement) and enjoy deep restorative sleep. This will assist to improve your circadian rhythm and as a result, your HRV. Set yourself a regular bedtime and wake time with 6-8 hours in between to improve your sleep.

5. Avoid Drinking Alcohol

Studies suggest that drinking alcohol can lower your HRV (reminder: a higher HRV score is what we are aiming for). The lingering effects of alcohol may decrease your HRV for the following 4-5 days after consumption. Avoid drinking alcohol or at least limit your intake if you want to improve your HRV.

To date, there is no technology on the market that will tell you which area listed above is responsible for low HRV. However, you can use your power of observation to assess what areas need attention in your own life. Often people are oblivious of many stressors in their lives until they measure what is going on in the body. Investigating and limiting various sources of physical, chemical, and emotional stress is the best way to improve your nervous system function and overall wellbeing.

Chiropractic adjustments are a great way to increase stimulation of the nervous system and to improve HRV.

HRV technology is a phenomenal tool to directly measure the nervous system function and demonstrate a system that is under stress. It can assist chiropractors to determine if and how that individual will respond to chiropractic care and other physical therapies.

So, I ask you to stop and think for a minute. Are you experiencing health issues that could be linked to different stressors in your life? Would you like to improve your health and wellbeing? If you answered YES to either of these questions, it is time to make an appointment with your chiropractor!

How Can HRV Inform Our Training?

HRV data can provide meaningful insights for planning your exercise and training. Different activities will influence HRV, so depending on your current score you can choose the exercises most appropriate to your situation. Below is a rough breakdown of score ranges and what they mean. Note: HRV is measured in milliseconds (ms).

HRV Reading / Score	Level of health
Below 50ms	Indicates UNHEALTHY HRV levels (low HRV)
Between 50ms – 100ms	Indicates a COMPROMISED state of health
100ms or higher	Indicates a HEALTHY state (high HRV)

When an individual is in the healthy HRV range, they can engage in performance training, such as high intensity exercises, to improve their athletic performance. Individuals that are at compromised levels (50ms to 100ms) would be wise to investigate and understand their individual HRV spectrum and what that means for them regarding physical activity. The closer you are to 100ms the more cardiovascular or resistance training you can engage in. On the other hand, the closer to 50ms you are, the more restorative the activity needs to be. Some great options for people in the lower range include gentle walking and yin-yoga. Massage and physical therapy are highly recommended for those in this lower zone also.

An individual in a sustained unhealthy zone (HRV lower than 50ms for an extended period) are likely experiencing disease or illness and are best to seek professional medical advice and intervention.

Another important factor to note is that no matter where your usual score sits, a slight drop-in HRV after a training session is to be expected BUT a significant drop likely indicates overtraining. High-intensity training will shift an athlete away from a healthy HRV either into or towards compromised health for 12-24 hours, perhaps even 48 if an event was particularly distressing, for example, competing in a 24-hour endurance event. The athlete should approach healthy levels again with appropriate rest and nutrition.

A high-intensity training session will lower HRV temporarily, however, a consistently low HRV suggests the individual is not allowing enough time for recovery.

As you begin to adjust your exercise regime based on these new HRV insights, allow two weeks before reassessing your HRV. It is normal for scores to fluctuate, and it can take two weeks or more for the body to display changes and give a reliable reading.

Developing habits that maintain a high HRV score will support your body to have an efficiently functioning heart and responsive nervous system, which can lead to improved outcomes for morbidity and mortality. Exercise, diet, hydration, and rest are all contributing factors to overall health and their influence is evident in HRV readings. HRV is a powerful measure to inform your training, your body’s response to training and your body’s response to lifestyle factors that affect your health and wellbeing.

Yours in health,

Dr Adam Epskamp

References

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