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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