The Negative Effects of Inactivity on Your Nervous System

by Ram

Office at Night by Edward Hopper *

In the Yoga Sutras, Patanjali describes styana (inactivity, sedentary) as one of the several distractions that serve as obstacles on the journey toward perfect health and enlightenment. Data gathered from 33 countries indicate that sedentary lifestyle accounts for six percent of all cases of coronary heart disease, about 7 percent of type 2 diabetes, and 10 percent of breast and colon cancers. That puts inactivity up there with smoking as a possible barrier to increasing life expectancy (see Inactivity 'killing as many as smoking'). 

A sedentary lifestyle is one in which, among other things, you sit for more than 3 hours, sleep for extended periods of time, watch long hours of TV, or simply idle away the time. But humans are designed for movement and physical inactivity is against the evolutionary norms for humans as the human body simply is not built to be inactive. Go back to history and notice that pre-historic men were always active—often quite strenuously—to get food, find shelter and simply survive. They naturally spent a lot of time outdoors walking, hunting, gathering, and performing various other physically oriented tasks. To them this was not a physical exercise or "working out"; it was just normal life.  In today’s world, however, activity/exercise is primarily an intervention—something we do to guard against the negative impacts of a sedentary lifestyle.

Inactivity is not only having an impact on public health but also seems to decrease the life span of the individual. Studies reported in prestigious medical journals suggest that prolonged inactivity is the cause of one in 10 deaths worldwide. Adults in the U.S. spend an average of 55 percent of their day engaged in some kind of sedentary behavior (see Sedentary behaviour and life expectancy in the USA: a cause-deleted life table analysis). Such prolonged inactivity puts an individual at risk for many chronic diseases, particularly cardiovascular disease, Type 2 diabetes, obesity, and high blood cholesterol. It also weakens the musculoskeletal system, increasing the likelihood of osteoporosis and the risk of falls and fractures. Those who maintain a reasonable amount of activity particularly across the middle and later years are twice as likely to avoid early death and serious illness compared to the inactive individuals. 

This reminds me of my earlier post The Power of Mental Exercise, Part 1 where I mentioned that our brain is "plastic," which refers to the brain's capacity to rewire itself through mental activity, learning and experience. When we learn new things, our brains put out new neural branches and form new connections; the brain constantly changes and rewires in response to experience and learning. Plasticity is the reason why stroke patients can relearn skills after sustaining brain damage. Plasticity also explains how a healthy part of the brain might assume the job of a damaged part. Studies have shown that physical and mental exercise rewires and remodels the brain. 

Having realized the ill effects of inactivity on the physical body, researchers took the next and the most obvious step of investigating the effects of inactivity on the brain and cognition. Very little is known about whether inactivity alters the structure of the brain and the subsequent consequences that arise as a result of this alteration. But common sense and our own personal experiences tell us that we feel depressed, dull, or gloomy after prolonged inactivity. Some of us even complain of “fogginess” or “murkiness” after idling away for prolonged periods. 

In order to obtain empirical data on the relation between inactivity and brain health, researchers performed experiments on mice. Scientists gathered two groups of rats and placed one half of them in cages with running wheels to keep the rodents very active. The other group was kept in cages that restricted their total activity so this group would remain sedentary. After three months, the animals were injected with a special dye that colors a specific set of neurons in the rostral ventrolateral medulla, a region of the brain that controls the autonomic nervous system (ANS) activities, including breathing, blood pressure, and other metabolic functions central to our existence. An advantage of monitoring this specific area in mice is that in humans this region of the brain functions similarly. When the ANS functions optimally, information from the neurons travels to the heart in a coordinated and regulated manner. This causes the blood vessels to either widen or contract as demanded by the situation. A disorderly and overly active ANS is problematic as it could turn on the sympathetic part of the system erroneously, which could result in faster heart and breathing rates, and increases in blood pressure. 

When the scientists dissected the brains of rats in the above-mentioned study, they found noticeable structural and functional differences between these two groups. Inactivity not only affected the neurons and brain function but the heart as well. While the neurons in the brains of the active rats were well shaped, had perfect branching, and were functioning normally, inactivity triggered unregulated and unrestricted neuronal branching making them hyper sensitive. This in turn resulted in erratic hyper-activation of the ANS and cardiovascular disease. In effect, these neurons had changed in ways that made them likely to over-stimulate the sympathetic nervous system, potentially increasing blood pressure and contributing to the development of heart disease. The findings are important as they address the mechanism by which inactivity increases the risk of heart disease. Though the study was primarily done in mice, the risks associated with inactivity can be extrapolated to humans as well.

By encouraging you to be physically and mentally active— helpful for preventing a whole host of health problems—we’re doing you a favor. Instead of idling away your time or sitting on the couch watching a TV show, there is no reason you can’t simply get off the couch and do a little bit of yoga, right next to the couch (or anywhere else in your house). This blog has got lots of mini practices that you can do. You could try a practice you find in a yoga book or DVD, or you could just start out with a Reclined Leg Stretch or a Downward-Facing Dog pose and see what happens next.  If you skip just one TV program, you can do a half an hour of yoga without even leaving the house (see Creating a Mini Yoga Practice). On our blog, we’ve got yoga poses you can do at work, at the airport, or anywhere else you can’t roll out a yoga mat. Whatever it is that you do, make sure you are more active and just have fun incorporating a home or office practice. You’ll be surprised at how rewarding it is!

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Falling for Yoga Myths: Yawning and Sighing and the Nervous System

by Nina

Heart and Lungs

I hope you realize by now that there are a lot of myths out there in the yoga world, such as that yoga nidra is an ancient practice or that Sun Salutations have been practiced for thousands of years. So here at Yoga for Healthy Aging, we try to do a bit of fact checking before we go ahead and write about a subject, whether it is medical, scientific, or historical. And when I edit a post, I try to confirm anything that looks a bit, well, suspect. But once in a while, I’m less than meticulous, and that can result in an error or two. After I read what Baxter wrote about the relationship between the breath and the nervous system in his post How Your Breath Affects Your Nervous System, I asked him to take a look at a related post I wrote some time ago called Your Key to Your Nervous System: Your Breath because I was concerned that perhaps my original post had errors in it. Although at the time I had been writing about what I was convinced were facts, Baxter confirmed that some of the information in my post about yawning and the affect of the breath on the nervous system, which I had learned from a yoga teacher, was actually incorrect. Baxter identified this misinformation as a yoga myth—ideas that seems to get perpetuated, despite the fact there is no proof of their validity.

So this post today is an update to my original post, with Baxter’s comments/corrections on my original statements. Well, it’s a journey for us, too, right?

YOGA MYTH: Nina wrote, “Have you ever wondered why you tend to yawn when you’re sleepy? Well, a yawn is a great big inhalation. And because your heart rate tends to speed up on your inhalation, that yawn in the middle of that boring lecture or business meeting is little message to your nervous system: wake up! On the other hand, when you are upset about something, you tend to sigh. That sigh—try one!—is an extra long exhalation. Because your heart rate tends to slow on your exhalation, that sigh while you are feeling emotional turmoil or are just stuck in traffic is a little message to your nervous system: take it easy, buddy, slow down a bit.”

BAXTER’S CORRECTION: Here’s what I found…and it does not seem to confirm your suggestions that it is the heart rate effects that are driving the yawn or sigh. There are four theories about why we yawn, none proven or much studied:

• Physiologic theory: Our bodies induce yawning to draw in more oxygen or remove a buildup of carbon dioxide. At least one studied seems to have disproved this theory.
• Evolutionary theory: Some think that yawning began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities.
• Boredom theory: Although we do tend to yawn when bored or tired, this theory doesn't explain why Olympic athletes yawn right before they compete in their event or why dogs tend to yawn just before they attack. It's doubtful either is bored.
• Brain-Cooling theory: a more recent proposal is that since people yawn more in situations where their brains are likely to be warmer—tested by having some subjects breathe through their noses or press hot or cold packs to their foreheads—it's a way to cool down their brains. Cool brains think more clearly.

Why do we sigh? As it turns out, sighs do seem to work like the brain’s reboot button for regular breathing. According to a 2010 study Take a deep breath: The relief effect of spontaneous and instructed sighs, during mental stress, the volunteers’ breathing became more and more irregular as participants increasingly relied on deliberate breath control, at which point, a sigh occurred, causing automatic regular respiration to kick in again. Furthermore, muscle tension steadily built up before a spontaneous sigh and decreased afterward, supporting the idea that sighing helps release tension.

YOGA MYTH: Nina wrote, “It turns out that by intentionally taking in more oxygen (either by speeding up your breath or by lengthening your inhalation) you can stimulate your nervous system and that by taking in less oxygen (by slowing your breath or lengthening your exhalation), you can calm yourself down. It’s that simple.

BAXTER’S CORRECTION: It is actually likely not that simple, as the effect I described in my post How Your Breath Affects Your Nervous System really more clearly explains what happens: the inhale speeds up the heart rate (not because of O2 levels) and the exhale slows it down (not due to O2 levels, but due to the nerve input from breath cycle to heart). As the heart rate slows more over the course of five minutes of 1:2 ratio breathing, for instance, the slower heart rate is monitored by the brain and leads to even further turning on of the parasympathetic Rest and Digest response. And, in fact, carbon dioxide levels in the blood stream have a much greater influence on the rate of breathing than O2 levels, and are monitored much more closely by the brain moment by moment and lead to adjustments in the ANS tone of whether sympathetic or parasympathetic nerves are stimulated. The importance of “getting more oxygen” in is a myth that has been propagated for a long time by yoga teachers in this country. For further information, see Leslie Kaminoff’s article What Yoga Therapists Should Know About the Anatomy of Breathing.

CONCLUSION: Well, we're all learning this stuff together. Even Baxter went ahead and did a bunch of new research. And, sigh, at least I was right about sighing.

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How Your Breath Affects Your Nervous System

by Baxter

When I read the posts of my fellow YFHA bloggers, I often learn new perspectives that might differ from my own as well as new information that I was previously unaware of. Reading the posts also highlights occasions where I could have been clearer or given better information on a particular topic. As an example, I have written about breath techniques and their effect on the autonomic nervous system, as did Timothy in his awesome follow-up post on the buzzing bee breath, Bhramari Pranayama with Mudras. And we often mention that extending or lengthening the exhalation triggers the parasympathetic nervous system, the Rest and Digest part of our nervous system’s balancing program. This made me realize that I could add a bit more detail to explain how that actually happens.

It turns out the Autonomic Nervous System (ANS) that connects brain to body is a two-way street. If I am anxious and nervous or stressed out by events in my life or simply the thoughts about those events, my brain, via the nerves of the ANS, will likely turn on the Sympathetic part of that system (the Fight or Flight response), which could result in faster heart and breathing rates, and increases in blood pressure, to mention just two of the most obvious physiological changes.

But the cool thing is that the lungs and heart can feed back to the brain and essentially convince the brain that things are calm and peaceful, even when there are still stressful circumstances. One neat way this happens involves the relationship of the heart and lungs and the nerves between them. In each round of breath, during your inhalation, your heart gets stimulated to beat a little faster. Then during the exhalation that follows, your heart gets told to slow down a tad. The overall effect is very little change in the heart rate from minute to minute. But when you make one part of the breath cycle, either the inhale or the exhale, longer than the other, and you do this for several minutes, the accumulated effect is that you will either slow the heart rate down or speed it up from where you started. When you make the inhales longer than the exhales, for example, by using a two-second inhale and a one-second exhale, and you keep this up for several minutes, the heart rate will go a bit faster. This will send a feedback message to the brain that things need to activate more in the brain and body for whatever work there is to be done, stimulating the Sympathetic portion of the ANS.

With the very useful Bhramari breath Timothy expanded on Bhramari Breath with Mudras, we do the opposite. As we hum during the exhalation, the exhales get longer relative to the inhales, as when we do a 1:2 ratio breath practice without the humming. This new respiratory cycle begins to slow down the heart rate, sending a message to the brain that everything is more peaceful and calm than five minutes ago, allowing the brain to support this shift further by activating the Parasympathetic portion of the ANS (the Rest and Digest or Relaxation response) that goes back from brain to body.

Research has shown that the vagus nerve as well as certain chemical neurotransmitters account for these effects of breath patterns on heart rate and subsequently on shifting the balance between the Sympathetic and Parasympathetic parts of the ANS. Keep in mind that the ANS is trying to keep all background systems in balance and responding appropriately to ever-changing circumstances of our day.

I’m providing this information for those of you who want to go a bit deeper in your understanding of how breath patterns affect the nervous system balance and either excite the system or quiet it. Our conscious choice of breathing differently can shift us to a more desirable part of the ANS, either by stimulating the active Sympathetic branch or the quieting Parasympathetic branch.  Most of us need more of the latter, but not always!

For a little more background on how the Respiratory system influences the Cardiac system, which in turn influences the Autonomic Nervous System, see The human respiratory gate as well as Effects of yoga on the autonomic nervous system, gamma-aminobutyric-acid, and allostasis in epilepsy, depression, and post-traumatic stress disorder.

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