Hey Readers! This blog post is part 2 of my “Yoga and the Autonomic Nervous System” series. If you have not read part 1 yet, I highly recommend that you go back and read part 1 (link here) before delving deeper into this information. However, I will summarize the information in part 1, so I can be sure we are all on the “same page” with regards to the autonomic nervous system (ANS). The ANS has two divisions – the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). Many people live with ANS dysfunction, or imbalance. Hyperactivity in the sympathetic nervous system tips the autonomic balance to SNS dominance.
But this sympathetic overactivity is very unhealthy to the body and mind and can cause A LOT of physical and mental issues (again, read part 1 for more information on this topic). We need to find time, several times throughout the day, to rest and relax so that our PNS can perform its maintenance operations in the body, counterbalancing the SNS.
In our modern society, we tend to gravitate towards pharmaceuticals and expensive medical procedures/treatments to help "fix" or "cure" our ailments. This is often because we are looking for the quickest way to deal with our issues. And, listen, I totally get it. When you are in pain or experiencing discomfort for any reason, of course it is natural to seek out the fastest acting interventions. However, sometimes medication comes with more side effects than the original reason you began taking it. And expensive medical procedures sometimes don’t even correct your original issue, or they only correct it temporarily.
But, did you know that it might totally be possible for you to reduce pain and increase wellness simply by balancing your ANS through some lifestyle changes? If you are willing to put in the work, consistently, you can affect real, lasting change in your body and mind. And let me be very clear - by no means am I telling you not to take your medicines or not to see your doctor. I am just offering another option that you might consider adding to your current wellness regimen that is backed by science.
Recall from part 1 of this series that the ANS is not within your conscious grasp (compared to your somatic nervous system, which is under your conscious control). Thus, you must use other “tricks” to create optimal conditions for it to function well. Luckily, there are several accessible methods that you can use to down-regulate your nervous system and increase parasympathetic dominance. Yoga is one such trick, as well as diet, sleep, breathing/meditation, and therapeutic massage. In this post, I will discuss how yoga can help to restore ANS balance, based on current scientific research (and my own personal experience sprinkled in as well).
Heart Rate Variability - How is ANS Functioning Typically Measured?
Before we dive deeper into yoga’s effect on the ANS, I want to take a few moments to explain how researchers actually determine changes in the ANS. Most of what we know about ANS functioning comes from measuring heart rate variability (HRV). ANS imbalance can be reflected in measures of HRV, and it is used in most research studies to indicate what is happening in the ANS. Most of the research studies that evaluate yoga’s effect on the ANS use HRV as the outcome variable. Essentially, HRV is the variation in time between each heart beat.
Your heart rate (HR) is not meant to stay at the same speed at all times. Your HR should change based on your activity and emotions. Your body is supposed to modulate your HR and blood pressure (BP) moment-by-moment to keep you alive, and this modulation is governed by the ANS. Having a high HRV means that your body can efficiently change your heart rate depending on your current environment (e.g. do you need to be calm and rested as when cuddling a sweet dog, or do you need to be alert and active as when running from an aggressive dog?). A low HRV will make it difficult for you to bounce back from stress, while a high HRV will allow you to deal with challenges gracefully and easily. Healthy hearts have higher HRV and sick hearts have poor HRV.
Your HR should be able to easily change based on your current environment.
Increased, or high, HRV is associated with parasympathetic nervous system activity. A higher HRV is an indicator of adequate adaptation to a given environment and effective functioning of the ANS. A lower HRV is an indicator of inadequate adaptation of the ANS and poor physiological function in the individual. Additionally, increased parasympathetic activity increases HRV and is associated with good health. Low HRV is associated with poorer health and involves higher sympathetic activity. Reduced HRV is a potential risk factor for: hypertension, heart disease, anxiety, depression, immune system issues, digestive problems, trouble sleeping, weight gain, and chronic pain (see part 1 of this blog series where I discuss ANS imbalance in more detail).
Yoga’s Effect on the ANS
Yoga involves a diverse range of mind-body practices such as meditation and relaxation (i.e. dhyana), breath practices (i.e. pranayama), and physical postures (i.e. asana) that aim to integrate the mind and body. Yoga is often referred to as a “mind-body medicine,” and it is often recommended as a non-pharmacological tool for managing stress.
The scientific literature has repeatedly shown that practicing yoga modifies ANS balance away from sympathetic dominance and towards parasympathetic dominance. These results were observed via increases in HRV in the research subjects who were assigned to a yoga practice experimental group, but not in subjects in the control group (i.e. those who did not engage in a yoga practice). Also, it should be noted that the ANS benefits were seen in both novice yogis AND advanced practitioners. And, in some studies, this ANS re-balancing was not seen in individuals who engaged in other forms of recreational exercise instead of yoga (e.g. team sports, running, weight-lifting, walking etc.). Finally, the increased PNS activity was observed in nearly all ages of participants (e.g. children, teens, adults, etc.).
The shift to PNS dominance after engaging in a yoga practice was associated with the following physiological and psychological benefits in the research studies:
Reduction in blood pressure (BP). Recall from part 1 of this series that when you increase PNS activation, it results in lowered BP. Since yoga increases PNS activity (as measured via HRV), it helps to lower your BP.
Reduction in stress hormones and reported stress levels. When you engage the PNS, it reduces the levels of stress hormones, such as cortisol, in your blood. This leaves you feeling calmer and more at ease. In fact, individuals who participated in a regular yoga practice reported improved quality of life as well as reduced anxiety, stress, and depression. Also, several studies showed reductions in blood cortisol levels after engaging in a yoga practice.
Reduction in reported pain levels. Recall from part 1 of this series that pain activates your SNS. The SNS activity further exacerbates your pain by keeping you in a "fight, flight, or freeze" response. The PNS dominance brought about through yoga helps to get you out of this vicious pain cycle AND gives your body a chance to heal.
Improved sleep. When you are in a sympathetic state, your body is in high arousal and alertness, which can make it very difficult to sleep. Additionally, if you are not activating your PNS enough during the day, your body will not have had a chance to perform maintenance operations, such as digestion, cellular repair, and elimination of waste products. This will also make sleep very challenging because your entire physiology will be "out of whack."
Improved tolerance of stressful or emotional situations. The research showed that those who engaged in a yoga practice recovered much quicker, and easier, after stressful or emotionally charged events, rather than staying "stuck" in an overactive sympathetic state. This improved emotional flexibility seems to stem from increased activation of the PNS from yoga.
Reduced resting heart rate (HR). Your resting HR is how fast your heart contracts each minute to pump blood to your organs and tissues. A high resting HR is associated with cardiovascular issues since your heart is working extra hard each and every minute to move blood around your body. A low resting HR means that your heart is very efficient at transporting blood around your body. When you are in a sympathetic state, your HR naturally increases (again, see part 1 of this series for more information). However, your HR should ideally decrease to a typical level when you no longer need your SNS to be "on." If you have ANS imbalance, your HR may stay elevated because your SNS is stuck in the "on" position. The research has shown that yoga helps to lower your resting HR, likely through PNS activation, leading to a healthier heart.
Improved digestion. As discussed in part 1 of this series, PNS activation causes increased blood flow to internal organs, including your digestive organs. This increased blood flow stimulates maintenance processes, such as digestion and elimination. When your body digests foods and liquids appropriately, you are less likely to experience gas pains, constipation, diarrhea, or other digestive issues. Also, when your digestion is running smoothly, you are able to extract more nutrients from your food, leading to better overall health in your entire body. The improved digestion is correlated with increased PNS activity as seen in those who engaged in a yoga practice.
Inhibition of areas in the amygdala responsible for fear, aggression, and rage. Your amygdala is an almond-shaped mass deep within each cerebral hemisphere of your brain, and it is responsible for experiencing emotions such as anger, fear, and aggression. Imaging and electroencephalograpy (EEG) studies showed that individuals who participated in a yoga practice showed reduced activity in certain parts of the amygdala, leading to better management and more healthy expression of emotions. Activation of the amygdala occurs during sympathetic dominance since your nervous system "thinks" you are in danger. Yoga helps to increase activity in your PNS, which allows for inhibition of the amygdala. This can help to reduce feelings of rage and aggression.
Reduction of PTSD symptoms. Post-traumatic stress disorder (PTSD) is a mental health condition that is triggered by a terrifying, or extremely stressful, event. Symptoms can include flashbacks, nightmares, and extreme anxiety. Research has shown that a yoga practice decreased PTSD symptoms (specifically, re-experiencing, avoiding and numbing, and hyperarousal) when compared to a control group AND to a group that received traditional psychotherapy alone. These effects were maintained 15 months after the yoga intervention. The reduction in PTSD symptoms is correlated with increased PNS activity.
Summary
ANS imbalance is unfortunately a very common issue today. Many people are not even aware that many, if not all, of their health issues stem from dysfunction in the ANS. Most research studies measure ANS functioning via heart rate variability (HRV). A higher HRV is associated with PNS dominance and healthier bodies and minds. A lower HRV is associated with SNS dominance and unhealthy bodies and minds. Yoga is a mind-body practice that aims to integrate breath, mind, and body through the use of physical postures, breath work, concentration, and relaxation. Several research studies have shown that yoga helps to increase activity in your PNS and decrease activity in your SNS. PNS dominance is associated with a wide variety of health benefits, including improved sleep, digestion, emotional processing, and blood pressure. Conversely, SNS dominance is associated with a wide variety of health issues including, weight gain, immunodeficiency, anxiety, trouble sleeping, and hypertension. Yoga may very well be a viable alternative, or addition, to medication and/or surgery. Yes, you have to be disciplined enough to regularly practice yoga in order to reap the ANS benefits. But, you can truly change your nervous system for the long haul simply by practicing yoga. So, get on Google and look for yoga studios in your area. Take a few classes and see how you feel after. Or, search for private yoga teachers in your area. If you are interested in private yoga sessions with me, Jackie, you can securely book through my website (go to top of page and click "book online"), or you can reach out to me directly to find out more about my services and background.
As always, the information presented in this post is derived from my own personal practice and study of yoga, neuroscience, and human movement. If you have specific questions about your nervous system, please consult with your physician. If you have not already, please subscribe to my newsletter by adding your email at the bottom of the page. This way you can "stay in the know" about my latest blog posts, coupons, and other health/wellness information. Special thanks to my incredible husband for doing all of the artwork in this post.
~Namaste, Jackie Allen, M.S., M.Ed., CCC-SLP, RYT-200, RCYT
References:
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Marieb, E.N. (2004). Human Anatomy & Physiology, 6th Edition. Pearson.
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