Improve Heart Rate Variability - What You Need To Know To Optimize

What is Heart Rate Variability (HRV)?

Heart rate variability (HRV) is the variation in the time intervals between consecutive heartbeats and is regulated by the autonomic nervous system (ANS), the part of your nervous system that regulates involuntary and unconscious physiological processes such as heart rate, blood pressure, and digestion.

The ANS consists of two branches: the sympathetic known for the 'fight or flight' response and the parasympathetic known for 'rest and digest'. It's best to think of HRV as a reflection of your body's ability to adapt to different stress responses —whether it's gearing up for action (sympathetic) or relaxing and recovering (parasympathetic).
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Why Optimize HRV?

Typically higher HRV scores are attributed to greater markers of well-being. Learning about and optimizing your HRV can therefore have a significant impact on various aspects of your life, including sleep quality, stress reduction, overall recovery, resilience enhancement, and even achieving a state of flow. By understanding and improving your HRV, you can take proactive steps to boost your overall well-being and change your day-to-day habits.
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Key Terms to Know:

• Artifacts: Data recording errors, such as irregular heartbeats, which may skew HRV readings. Some tracking devices and the type of measurement they use may include more artifacts than others.
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• Resonance: To achieve a state of coherence and be within the natural frequency of the human body. This is typically done by breathing at a frequency of 0.1 Hz (equivalent to 6 breaths a minute or consistent inhales of 4 seconds and exhales of 6 seconds).
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• Coherence: A state of mind, heart, and emotional alignment, associated with optimal well-being.
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• Vagus Nerve: The 10th cranial nerve - an extremely important nerve that starts at the top of the spine and transcends down into your digestive system. It is responsible for regulating various bodily functions, including heart rate and digestion.
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• Vagal Tone: The activation and activity of the Vagus nerve. Many breath work practices the centered around increasing the vagal tone.
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• Hertz (Hz): Measurement unit for frequency bands in HRV analysis. The number of hertz is equivalent to the number of cycles per second.
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How to Measure HRV

Most HRV devices are wearables you see on the market today use Photoplethysmography to measure HRV (PPG). PPG is a simple process that involves using a small infrared sensor to track blood volume changes through the skin. These changes are measured via changes in heart rate and pulse rate and are key to providing insights into HRV.

There are two main different types of HRV measurements: frequency domain measurements and time domain measurements.
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Frequency Domain Measurements:

Frequency domain is a complex analysis technique that shows how much of a signal lies within one or more frequency bands (ranges). Within HRV there are four different types of frequency bands: ultra-low frequency, very low frequency, low frequency, and high frequency. Devices in today's market do not measure the ultra-low frequency and very low frequency bands, however, it is important to know that all bands are active simultaneously and some are more dominant and more present than others.
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Low-Frequency Measurements

The low-frequency band has a wavelength range of 0.04-0.15Hz and is influenced by both parasympathetic and sympathetic activity. The dominance of the low-frequency band can be easily manipulated through breathwork and meditation techniques, such as Buteyko or Box breathing, and is likely a representation of autonomic balance. It takes up to 2 minutes to take an accurate reading of the low-frequency band.
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High-Frequency Measurements

The high-frequency band has a wavelength range of 0.15 to 0.4Hz and is primarily associated with parasympathetic activity and cardiac control. Lower high-frequency band scores are associated with lower levels of stress and anxiety while the opposite is true for higher high-frequency band scores. It takes up to 1 minute to take an accurate reading of the high-frequency band but the longer the measurement time the better.
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Time Domain Measurements:

Time domain measurements are measurements of the time intervals between heartbeats, measured in milliseconds. There are two main time domain measurements: SDNN and RMSSD:
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SDNN (Standard Deviation of NN Intervals)‍

‍SDNN is the standard deviation of inner beat intervals of normal sinus beats. This means that the measurement measures the time interval between consecutive heartbeats but removes abnormal beats (artifacts) from its measurement to get a more accurate reading. SDNN measurements can be taken within 5 minutes but are best when taken over 24 hours. The SDNN is great for reflecting overall HRV scores and is used as an HRV measure in Apple Watch devices.
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‍*SDRR - A measurement of the inner beat intervals for all sinus beats, including artifacts such as abnormal or false beats. It is important to be aware of the SDRR when purchasing HRV devices to prevent inaccurate measurements.
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RMSSD (Root Mean Square of Successive Differences)‍

‍The RMSSD is a measure of parasympathetic activity and vagal tone, offering great insights into overall recovery and stress levels. It can't be influenced via movement or breath and is frequently used by health-tracking devices such as the Oura ring and Whoop.
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Moving the Needle

Although devices such as the Oura Ring and Whoop are great for overall recovery scores, they are unable to provide the real-time HRV frequency domain band measurements.

To overcome this, I have opted to use both my Oura ring and the Polar H10 heart rate strap. The Polar H10 is a brilliant device that can be paired with its Elite HRV app to access all the HRV data you could need and provide a clear snapshot of your physiological processes. I like to wear it for the first 5 minutes of my day, when sitting in bed as well as during my daily breathing and meditation exercises so I can see the fluctuations in my HRV.

For a comprehensive guide and review of the Polar H10 and how it works, feel free to read the article here.

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Lifestyle Interventions

Although measuring and being aware of your HRV is a great tool for optimizing your health and well-being, I'm a big believer that you should master and dial in on the basics of health before adding in other practices and therapies.

1. Sleep - Optimizing your sleep is the easiest thing you can do to optimize your health and well-being. Not only will it help your energy and well-being but is a key factor in increasing HRV. For more information on how to optimize your sleep, check out my Sleep Advantage course here.
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2. Exercise: It may seem obvious but engaging in regular physical activity will help to improve overall fitness and enhance your HRV.
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3. Cold Therapy - Incorporating cold exposure techniques like cold showers or cold plunges, is a great way to stimulate the autonomic nervous system and improve resilience. For more information on cold plunges and how to build your own, feel free to check out the video here.
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4. Breathwork: From box breathing and the Buteyko method to resonance breathing and the Wim Hof method, there are several breathing techniques out there that can help you build your vagal tone and increase your resilience to stressors.
   
   I'm personally a huge fan of the Buteyko method and would highly recommend checking out Patrick McKeown's 'The Oxygen Advantage'.
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Conclusion

In conclusion, understanding and optimizing heart rate variability can have profound effects on your health, well-being, and performance. By implementing lifestyle interventions, monitoring HRV trends, and choosing the right tracking device, you can take proactive steps toward achieving optimal an HRV and unlocking your full potential.

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For a more in-depth explanation and complete HRV guide, watch the video here.