Heart-Rate Variability Explained.
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What is Heart-Rate Variability?
The autonomic nervous system* is our brain’s most elementary survival system.
Structurally, it is made up of the midbrain (known as the limbic system, which governs emotion) and brainstem regions (known as the ancient brain, which governs automatic, regulatory functions), along with their collective nerve projections down the spine and out to the body.
Functionally, it has two branches which act in opposition to one another all day, every day:
The sympathetic nervous system (SNS) - when activated this branch elicits the release of chemicals like adrenalin to fuel the brain and body for a short-term burst of action.
The parasympathetic nervous system (PNS) - when activated this branch elicits the release of chemicals like acetylcholine to help regulate basic bodily functions like digestion, wound healing and sleep, all of which are useful for our longterm survival.
At our best, these two systems work closely together to keep us in an optimal state of engagement within ourselves and our environments.
Heart-rate variability (HRV) measures the relative balance between these two systems, and here’s how:
When we inhale we stimulate the SNS, which increases our heart rate. When we exhale we stimulate the PNS, which decreases our heart rate. In healthy individuals inhaling and exhaling produce steady, rhythmical fluctuations in the interval between heartbeats as both systems kick into gear for their role. Accordingly, poor HRV is a lack of steady, rhythmical fluctuation in the interval between heartbeats, meaning the SNS and the PNS are out of sync or ‘shut down’ (commonly seen in trauma victims), as shown below.
Put simply, HRV is the pattern of the heartbeat and the tool through which we can gauge the health of our nervous system. The heart and the nervous system communicate with one another via the vagus nerve.
Why is HRV Important?
Good HRV is a measure of basic well-being. A strong, balanced nervous system gives us the ability to accurately respond to and recover from physical, emotional and mental stress. For example, individuals with good HRV will have a reasonable degree of control over their response to frustrations and disappointments, enabling them to calmly assess what is going on when they feel, let’s say, insulted or left out.
As long as we can manage to stay calm we are not slaves to our impulses and emotions, we can instead choose how we want to respond and keep that response in line with our broader social intentions. So, instead of telling your partner or boss to “go fuck yourself” in a moment of intense emotional arousal, you might perhaps choose to politely excuse yourself, take a few deep breaths and not change the course of your life in a regrettable instant?
Individuals with poorly modulated nervous systems are easily thrown off balance, both mentally and physically. Since the autonomic nervous system organises arousal in both the body and the brain, poor HRV not only has negative effects on thinking and feeling but also on how the body responds to stress. The biological systems that are meant to help us cope with the fluctuations of life fail to meet the challenge.
How to Measure Your HRV?
Technology means pretty much everything is accessible to us through our phones these days, and instant daily information on our HRV is no exception. I use a free app called Elite HRV which requires you to sync it with a compatible monitoring device, generally a chest strap. A list of compatible devices can be found here, they are all available to buy on Amazon and will set you back about €70. I use the Polar H7, which is an entirely optional but worthy investment if you’re passionate about health, fitness and well-being.
Just to note, Fitbit or any similar device does not measure HRV. They measure the number of heartbeats per minute (or heart-rate). HRV and heart-rate are mutually exclusive, one does not predict the other.
How to Improve HRV?
Robust HRV equates to longterm physical and mental health, so even if you don’t get around to measuring yours, you can still make informed lifestyle choices that will strengthen this vital function.
According to the research, the two most effective ways to markedly increase HRV are marathon running or yoga. Both, if you’d like to be overly certain.
The eastern practices of martial arts and Qigong have also proven to be effective. All of these practices train the body to slow the breath and synchronise it with the heart rate, resulting in a state of ‘cardiac coherence’ like that seen in the first illustration above. Yoga, in particular, has proven to be such an effective tool that leading psychiatric programs for suffers from post-traumatic stress disorder - which is marked by very poor HRV - include it for its profound benefits in this area.
If you find this topic interesting (and especially if you plan to invest in a device to measure HRV), Ben Greenfield has a great podcast where you can delve a little deeper and learn more:
*It is also called the ‘involuntary nervous system’, contrasting with the ‘voluntary nervous system’, which is concerned with conscious, voluntary movement involving ‘motor’ regions of the brain communicating with our skeletal muscles.
References
Grossman, P., et al. (2004). “Mindfulness-Based Stress Reduction and Health Benefits: A Meta-Analysis”, Journal of Psychosomatic Research 57: 35 - 43
Khalsa, S. B. (2004). “Yoga as a Therapeutic Intervention: A Bibliometric Analysis of Published Research Studies”, Indian Journal of Physiology and Pharmacology 48: 269 - 85
Kirkwood, G., et al. (2005). “Yoga for Anxiety: A Systematic Review of the Research Evidence”, British Journal of Sports Medicine 39: 884 - 91
Philippot, P., Chapelle, G. & Blairy, S. (2002). “Respiratory Feedback in the Generation of Emotion”, Cognition & Emotion 16, no. 5: 605 - 627
Pilkington, K., et al. (2005). “Yoga for Depression: The Research Evidence”, Journal of Affective Disorders 89: 13 - 24
Sack, M., Hopper, J. W. & Lamprecht, F. (2004). “Low Respiratory Sinus Arrhythmia and Prolonged Psychophysiological Arousal in Posttraumatic Stress Disorder: Heart Rate Dynamics and Individual Differences in Arousal Regulation”, Biological Psychiatry 55, no.3: 284 - 90
Sovik, R. (1999). “The Science of Breathing: The Yogic View”, Progress in Brain Research 122: 491 - 505
Van Der Kolk, B. (2014). The body keeps the score: Mind, brain and body in the transformation of trauma. Penguin: UK