Updated: Aug 23, 2021
and can be found by visiting this link Longer Exhalations Are an Easy Way to Hack Your Vagus Nerve Respiratory vagus nerve stimulation (rVNS) counteracts fight-or-flight stress. Posted May 09, 2019
This post is a follow-up to "Diaphragmatic Breathing Exercises and Your Vagus Nerve," from that earlier series of posts. I'm excited to update what was primarily speculation a few years ago with some new scientific literature (Gerritsen & Band, 2018 and De Couck et al., 2019). These studies corroborate that longer exhalations are an easy way to hack the vagus nerve, combat fight-or-flight stress responses, and improve HRV.
What is HRV? Heart rate variability represents the healthy fluctuation in beat-to-beat intervals of a human or animal's heart rate. During the inhalation phase of a breathing cycle, the sympathetic nervous system (SNS) facilitates a brief acceleration of heart rate; during exhalation, the vagus nerve secretes a transmitter substance (ACh) which causes deceleration within beat-to-beat intervals via the parasympathetic nervous system (PNS).
HRV is used to index the robustness of someone's vagus nerve responses and vagal tone (VT). Higher HRV is associated with stronger vagus nerve function, lower chronic stress levels, better overall health, and improved cognition. Although clinical research on HRV doesn't always discuss the vagus nerve, it's well established that HRV is an effective way to index vagal tone and gauge the robustness of someone's physiological ability to counteract SNS-driven fight-or-flight stress responses.
L-O-N-G Exhalations are Key
Nota bene: I grew up in a household with a neuroscientist father, Richard Bergland (1932-2007), who was also the author of The Fabric of Mind. My dad idolized Nobel-prize winner Otto Loewi (1873-1961), who discovered the first neurotransmitter (acetylcholine), which is the chief neurotransmitter of the PNS. What we now refer to as acetylcholine or ACh was originally coined "vagusstoff" (German for "vagus substance") by Loewi around 1921.
In a simple but elegant experiment on frogs (that came to Loewi as a Eureka! moment in a dream), he found that a tranquilizing substance squirted directly out of the vagus nerve onto the heart, which caused a frog's heart rate to slow down immediately. (See, "How Does 'Vagusstoff' Calm Us Down?")
As a tennis player, my father used the same breathing techniques he used in his neurosurgery operating room to stay calm. He taught me the basics of how to use deep, slow breathing techniques to hack the vagus nerve and slow down my heart rate, just like a frog in Loewi's lab.
Dad kept his neuroscience lessons on the tennis court simple. He'd say, "If you want to maintain grace under pressure, visualize squirting some vagusstoff into your nervous system by taking a deep breath—with a big inhale and a long, slow exhale—as you bounce the ball four times before every serve."
Without going into too much detail, my father taught me that by increasing the duration of my exhale after taking a deep breath, I could trigger my vagus nerve to squirt out some stress-busting "vagusstoff" on demand. This "stuff" was like a self-made tranquilizer that would relax my nerves and help me avoid choking or double-faulting during match points.
Later, as a student at Hampshire College, I practiced yoga regularly and was guided by an instructor who also emphasized the importance of focusing on the inhalation/exhalation ratio during yogic breathing exercises. Although he didn't mention anything to do with neurobiology or psychophysiology, it was clear that many of my instructor's breathing techniques emphasized longer exhalations, just like my father had taught me.
Based solely on life experience, I saw a parallel and had a hunch that these centuries-old methods of shifting the inhalation/exhalation ratio that often had long-winded Sanskrit names such as "bhastrika pranayama" were ancient vagal maneuvers unwittingly designed to hack the vagus nerve long before Otto Loewi discovered vagusstoff.
It's reassuring to have fresh research corroborate that each of us can trigger a "relaxation response" (Benson et al., 1975) simply by focusing on the inhalation-to-exhalation ratio of our breathing and consciously extending the length of each exhale while doing breathing exercises as we go about our day-to-day lives.
One gadget-free way to track the timing of your inhalation-to-exhalation breathing cycles per minute is to use a 4:8 ratio of four-second inhalations and eight-second exhalations. This breathing cycle takes 12 seconds which equates to five inhalation/exhalation cycles per minute. Based on road-tested outcomes, I really like the 4:8 ratio because it's easy to use my right hand to count up to five with each digit and use the fingers on my left hand like an abacus to keep track of each one-minute cycle.
Anytime you want to hack your vagus nerve to reduce stress or improve decision-making, a simple self-talk script could be: "I'm stressing out. In order to calm down so I can perform better on this decision-making task, I'm going to take two minutes (right now!) to do 10 rounds of vagus nerve breathing based on a 4:8 inhalation-to-exhalation ratio."
During the four-second inhalation phase, I'd recommend breathing in through your nose—as you relax the back of your eyes and visualize filling up your lower diaphragm with oxygen—and slowly count to four. Then, I'd recommend exhaling through pursed lips (as if you're blowing out lots of candles on a birthday cake) as you slowly count to eight.