Site logo

Heart Rate Variability

a strong HRV builds stress resilience

Heart Rate Variability | Biohacking your body
12 November 2023 | James Kearslake
Table of Contents
Fun Fact

NASA played a role in developing red light therapy in the 1980s. NASA experimented with red light therapy to promote plant growth in space; its research led to the discovery of its health benefits for humans and contributed to the development of modern red light therapy devices.

What is Heart Rate Variability (HRV)

The heart’s rhythm is a vital indicator of our overall health and wellbeing, and our HRV is key to determining our body’s ability to handle, and move on from stressful situations.

Our lives are full of stressors, internal and external triggers, and our body is adapted to respond to these for our safety. Yet, if we are unable to bring our body down from heightened states of awareness, we live in a prolonged state of fight or flight, which has damaging consequences of our health physically, mentally, and emotionally.

HRV is an indicator of how well our body can respond to stress, and how efficiently it comes down from stress into a state of homeostasis or calm.

Heart rate variability itself is the variation in time intervals between successive heartbeats. While it may seem counterintuitive, a healthy heart doesn’t beat at a constant rate; it exhibits slight variations between each beat.

HRV should not be viewed as an irregularity, but instead a complex and dynamic process that is influenced by varying factors within the human body, including the autonomic nervous system (ANS).

The ANS, consisting of the sympathetic and parasympathetic branches, plays a pivotal role in regulating the heart rate. The sympathetic system revs up the heart rate, while the parasympathetic system slows it down.

HRV is, in essence, a reflection of the balance between these two systems and the heart’s ability to adapt to different situations.

A picture of a muscly man checking his heart rate on his Whoop watch having been for a run in the hills_benefits of tracking heart rate

Why HRV is Important

  1. Stress and Resilience – HRV is a useful indicator of our body’s stress response. A higher HRV suggests that the body is resilient and can adapt to internal and externals stressors well, while a lower HRV can indicate a person’s lack of adaptability, leaving the individual more vulnerable to stress-related health issues.
  2. Cardiovascular Health – HRV is linked closely with cardiovascular health. Research shows that individuals with higher HRV have a lower risk of heart disease, as it indicates a heart that can efficiently respond to the body’s many varying demands.
  3. Athletic Performance – Athletes and sports enthusiasts use HRV to monitor their physical condition. A higher HRV is often associated with better training capacity and improved recovery.
  4. Psychological Wellbeing – HRV is also a marker of psychological wellbeing. Lower HRV correlates with conditions like depression, anxiety, and post-traumatic stress disorder.
A picture of a smartwatch showing tracking of heart rate variability_best heart rate variability trackers

Why High HRV Indicates High Resilience

Heart rate variability (HRV) serves as a window into the body’s ability to cope with and adapt to stress, both internal and external.

A higher HRV indicates a well-regulated autonomic nervous system (ANS), which is key to resilience and adaptability in the face of stressors.

  1. Autonomic Nervous System Balance – The autonomic nervous system consists of two branches; the sympathetic nervous system, or our ‘fight or flight’, and the parasympathetic nervous system, or our ‘rest and digest’. These two systems operate opposing functions and continually regulate the body’s various involuntary functions, including heart rate. A higher HRV indicates a harmonious balance between these two branches, suggesting the body can switch efficiently between states of arousal and relaxation as needed. More on this below
  2. Quick Response to Stress – When faced with a stressor, whether it’s a physical or emotional threat, the body with higher HRV can rapidly adapt. The parasympathetic system, responsible for relaxation, can quickly counteract the sympathetic system’s stress response, preventing prolonged periods of heightened heart rate and blood pressure. This ability to shift gears efficiently, especially when reducing the levels of stress within the body, prevents wear and tear on the body’s vital systems from prolonged stress and inflammation.
  3. Enhanced Recovery – After experiencing a stress trigger, the body with higher HRV recovers more effectively. The parasympathetic system helps restore homeostasis, bringing the body back to a state of calm and balance. This quicker recovery time is vital for minimizing the long-term negative effects of stress on the body, such as chronic inflammation and cardiovascular strain.
  4. Optimal Cognitive Function – A balanced ANS also aids optimal cognitive function. It allows for improved focus, better decision making, and the capacity to navigate challenging situations with greater clarity.
  5. Psychological Resilience – Individuals with higher HRV often exhibit greater psychological resilience. They can manage stress, anxiety, and emotional challenges more effectively, leading to improved mental health and wellbeing.

A higher HRV indicates a body’s ability to adapt to varying situations. This adaptability and resilience offers numerous benefits to our health as it significantly reduces the risk of chronic disease, inflammation and enhances our mental wellbeing and cognitive function.

Healthy HRV Values

Healthcare professionals assess HRV using various metrics and analyses, but typically, they look for the following characteristics in healthy HRV:

  1. Higher Total Power – A healthy HRV reading often exhibits higher total power in the frequency domain analysis, indicating greater variability and adaptability of the heart.
  2. Higher RMSSD – The root mean square of successive differences (RMSSD) is a time domain metric that reflects parasympathetic activity. Healthy HRV typically shows a higher RMSSD value.
  3. Balanced Sympathetic and Parasympathetic Activity – A balance is sought between the sympathetic and parasympathetic branches of the autonomic nervous system. An overactive sympathetic system may indicate stress or discomfort, whereas an overactive parasympathetic system might suggest sluggishness or fatigue.


Best HRV Wearables 2023

WHOOP – best overall for physical performance, recovery, and sleep

Leading in the market is Whoop; it’s technology is worth every penny you spend. It is by far one of the most expensive, but monitors every aspect of your life including movement, recovery, sleep, and can even tell you what intensity your body can train at one that day. It is one of the most reliable wearables for analysing what’s going on inside you, in easy to understand data within the app. Whoop is a ground-breaking piece of kit and is far ahead of their competitors in terms of technology, data, and future potential.

Fitbit Inspire 3 – best for physical performance

Garmin Forerunner 255 – best running watch

Polar H10 – best for a chest wearable

Oura Ring – best for sleep

Apple Watch Series 8 – best for varied functionality

Unhealthy HRV and Underlying Health Conditions

Unhealthy or worrisome HRV values can be indicative of various health conditions:

  1. Heart Disease – A consistently low HRV can be a sign of heart disease. It reflects the heart’s reduced ability to respond to changing demands and may indicate an increased risk of cardiac events.
  2. Stress and Anxiety – Chronic stress and anxiety can lead to lower HRV. Over time, this can contribute to the development of mental health conditions and cardiovascular problems.
  3. Inflammation – Inflammatory conditions, such as autoimmune diseases, may lead to decreased HRV. Inflammation can disrupt the balance of the autonomic nervous system.
  4. Diabetes – Reduced HRV has been associated with diabetes and impaired glucose metabolism.
  5. Sleep Disorders – Conditions like sleep apnoea can negatively affect HRV, as they disrupt normal sleep patterns and induce stress on the body.

Check your HRV

HRV can be calculated by smart watches and mobile apps, however these will always come with less accuracy than calculations determined by healthcare professionals.

For those interested in monitoring their HRV, options include:

  1. Heart Rate Monitors – Wearable devices, such as fitness trackers and smartwatches, can measure HRV. They are often convenient for continuous monitoring.
  2. ECG (Electrocardiogram) – For more accurate and detailed readings, healthcare professionals can perform an ECG. It provides a comprehensive analysis of HRV.
  3. Mobile Apps – Numerous mobile apps are available that use the phone’s camera to measure HRV by tracking changes in the colour of the fingertip.

Improve your HRV

Improving your HRV is an important objective for those looking to build resilience to stress. Particularly for high performers, business people, and fitness enthusiasts, improving your HRV is important to managing the body’s ability to cope with, and come down quickly from stressful situations.

The key to improving our HRV is balancing the autonomic system (ANS), which encompasses both the sympathetic and parasympathetic nervous systems. Over time, effective management of both branches leads to improved variability of heart rate.

As with all physiological improvements, lifestyle choices and habits are the determinants of the health of our body. To improve HRV, you need to be making the right lifestyle choices:

  1. Physical Activity – Consistent exercise, especially aerobic and cardiovascular workouts, have significant benefit to our HRV.
  2. Healthy Diet – Nutrition is one of the founding principles to positive health. Keep your nutritional intake natural with lots of fruit, vegetables, proteins, and good fats, and you will see significant improvements to your overall cardiovascular system and HRV. The mediterranean diet is known being for the healthiest for the heart and brain, so if in doubt, go Greek.
  3. Adequate Sleep – Prioritise a consistent sleep schedule. You need to be aiming for 7-9 hours of quality sleep per night, depending on your individual needs. Personally, 7 is never enough for me, and 9 too much. Find your magic number and stick to it. Mine is 8.25.
  4. Limit Caffeine – Caffeine is great for your cardiovascular system and cognitive function when consumed in responsible quantities. Too much caffeine and your body’s sympathetic nervous system, or fight or flight, will be unnecessarily activated with nowhere to expend its adrenaline. A build or adrenaline or cortisol causes chronic inflammation in the system, and over the long-term has a damaging effect to overall health including your HRV. I have one strong coffee each morning, and a green tea at lunchtime.
  5. Avoid Alcohol – Life is for living, so nobody is saying go sober. But alcohol is extremely damaging for the body and mind so it should be seen as a recreational activity that you allow as a treat. It should not be consumed daily. Those who only drink alcohol every few weeks will experience greater shifts in their overall health, training, recovery speed, and cognitive function. These overall improvements give your body the best chance of improving its HRV.
  6. Activate Parasympathetic Nervous System – Engage in activities that activate the parasympathetic nervous system, or ’rest and digest’, like yoga, meditation, deep breathing exercises, or a hot bath. Improving our ability to activate the parasympathetic nervous system helps our body efficiently enter rest and digest after stressful events. More below on the parasympathetic nervous system
  7. Social Connection – Building and maintaining strong social relationships positively influences our mental and emotional wellbeing which also benefits our HRV.

The Importance of a Healthy Parasympathetic Nervous System

Maintaining a healthy parasympathetic nervous system (PNS) is critical.

The PNS calms our system, preventing the body remaining in a heightened state of alertness, being flooded with adrenaline and cortisol, and helps bring us back to a state of homeostasis. Homeostasis the body’s natural point of balance, where our internal biological processes are operating optimally for our overall health, wellbeing, and cognitive performance.

  1. Stress Management – A robust PNS enables the body to respond to stress more effectively, mitigating the harmful physiological effects of chronic stress. It fosters resilience and reduces the risk of stress-related illness.
  2. Heart Health – The PNS helps control heart rate and blood pressure. A well-functioning PNS can prevent excessive wear and tear on the cardiovascular system, reducing the risk of heart disease and high blood pressure.
  3. Digestive Health – The PNS plays a central role in digestion. An active PNS helps regulate gastrointestinal function, promoting better nutrient absorption and digestive health, as well as supporting the critical healthy gut-brain axis by maintain a healthy vagus nerve.
  4. Mental Wellbeing – A healthy PNS directly results in positive mental health. It helps alleviate and prevent anxiety, depression, and other general mood disorders.
  5. Recovery – The PNS facilitates recovery after physical exertion and stress, helping the body enter its recovery state more efficiently.
  6. Longevity and Quality of Life – Research suggests that individuals with higher HRV, indicative of a well-functioning PNS, tend to live longer and enjoy a higher quality of life in their later years.

HRV is as a strong indicator of overall health and adaptability to stress.

By effectively managing both branches of the autonomic nervous system and promoting a healthy parasympathetic nervous system, individuals not only improve their HRV, but also enhance their overall wellbeing, reduce the risk of chronic diseases, and lead a happier, more fulfilling life.

Prioritising a balanced ANS and nurturing a resilient PNS is key to those looking to live long, healthy, and happy lives, while remaining successful and cognitively astute into old age.

Final Thoughts

Heart rate variability is a valuable metric that is key to understand early on.

The sooner you can identify your HRV and begin making improvements, the sooner you will directly improve your ability to perform under stress at work, in business, and when dealing with other stressful live events that unfold.

More than ever, with the constant economic and geopolitical challenges that we have seen since 2020, one’s ability to handle stress and uncertainty is crucial to maintaining your physical and mental health.

If budgeting allows, we recommend everyone invest in the Whoop as the product of choice. The data points that you will get from Whoop, for every aspect of your life, will be a defining moment in your self-awareness of your health and wellbeing.

Thanks to its detailed analysis of your fitness, recovery, HRV, and sleep, as well as other key metrics in your life, you will be immediately inspired to make lifestyle changes that significantly enhance the quality of your life.

Whoop is an investment in every person’s future, especially for those looking to build longevity, remain healthy, and prevent cognitive decline as we enter our old ages.

Who is James Kearslake?

Having been biohacking my mind and body long before it became fashionable, I’ve always lived by the benefits of nature’s resources to improve cognitive and physiological performance. Using my years of experience, products, and wellness practices, I’m now helping others elevate their cognitive performance to help build the life they want. I save you the time I’ve spent learning, so you can focus your time on building.

Proudly AI Supported

I proudly use AI to support development of my articles. As a heavily dyslexic person, writing can be a time consuming process with words often jumbled up and sentences the wrong way round. AI has become my crutch; allowing me to share the immense interest in my mind, while making content creation quicker and more accurate. AI is my benefit.

Did you find this useful?
If so, please do share it with others who may also benefit from it.

Affiliate Policy

We only ever recommend products we know offer value to our readers and that we use ourselves.

When recommending these products, we often include affiliate links so that we earn a small commission on sales made, at no expense to you as the reader.

Affiliate commissions are similar to an advertising fee which retailers pay to website owners, and is often the only way website owners can earn money through the content they create. Therefore, we hope you can support us by using our affiliate links if you decide to purchase products after reading our content, as it helps keep the website operating.

Thank you for always sticking by us, and don’t forget to join our newsletter to get ground-breaking content direct in your inbox.

Join thousands of Humans
achieving peak performance

For Body & Mind

we share interesting content,
that develops body and mind.

We are Humans

where are all humans are equal

We are Humans logo

join the community here: