Unpacking the Autonomic Nervous System For Health

By Sarah Casey and Michol Dalcourt

Stress. It can make it hard to sleep, hard to focus and hard to keep our cool. Strategies for reducing stress have become more and more popular as we try to grapple with chronic levels of stress and overwhelm in our lives.

At the same time, the science behind stress has become mainstream. Sure, we want to reduce our stress, but we also want to know what’s causing it and how we can prevent it from becoming a chronic issue.

Nervous science

It starts with our body’s autonomic nervous system (ANS), which controls involuntary body processes like breathing, digestion and heart rate. The ANS is divided into two main branches: the fight-or-flight sympathetic nervous system (SNS) and the rest-and-digest parasympathetic nervous system (PNS).

When we encounter physical, emotional or mental stress, our sympathetic system becomes more active, revving up our heartbeat and breathing rate, dilating our pupils and putting us on high alert. An active SNS makes us ready to react quickly and perform at a high level. In past millennia, it might have enabled us to outrun a lion or survive a battle, while in modern day, it helps us crush a presentation for our boss, score a touchdown on the football field or deal with the aftermath of a fender bender.

The parasympathetic system is responsible for calming our bodies back down to our physiological set point—normalizing our heartbeat, our breathing and returning our pupils to normal (where “normal” is, of course, different for every person).

The SNS and PNS can seem like opposing forces pulling our bodily processes in different directions. However, the precise effect is more complex—sometimes both systems are active at the same time. The key to a healthy ANS is having the two branches balance each other out—but not like two sides of a scale, with equal amounts on either side that keep the scale from moving. Instead, ANS balance is more like a teeter-totter with two kids on it, one child flying up while the other moves down and gets ready to push up again. The SNS helps us rise to challenges, and the PNS helps us recover and prepare to meet the next challenge.

Balance is all about flow

The ANS balance is a flowing balance, just like the teeter-totter. At any instant in time, it looks out of balance, but overall, each rider gets roughly equal time flying in the air and pushing from the ground. When these two branches lose their balance, we end up with problems like sympathetic dominance, aka chronic stress. Like when your dad would get on the other side of the teeter-totter—you knew you were going to be stuck up there until he let you down!

Parasympathetic dominance can be a problem, too, if it reduces our blood pressure or heart rate lower than our physiological requirement (that set point we mentioned earlier). Athletes, for example, tend to have a lower resting heart rate than the general population. It can get as low as 35 beats per minute, thanks to the efficiency they develop during training. But if the average senior citizen’s heart rate drops below 60 beats per minute, it can mean his or her body isn’t getting enough oxygen, putting him or her at risk of fainting, falls and even heart failure.

Finding balance doesn’t mean checking out

Stress isn’t all bad. Without it, we would never trigger the micro-tears that help us build muscle or the energy systems that make us more efficient at running. Relaxation isn’t all good, either—sometimes we need to pump ourselves up or we won’t be ready to improvise when we forget the next line of our presentation in the boardroom or ready to react in our favorite sport.

While we can’t always control the balance of stress in our work and home lives, in the gym, we can stimulate SNS or PNS activity with different styles of movement and breath work.

Parasympathetic stimulating activities

Let’s face it, most of us are not suffering from too much chilling out. We’re doing more in less time with fewer resources and feeling like we have less to show for it. No wonder most advice about balancing the ANS has to do with increasing parasympathetic activity!

Parasympathetic activity is directly related to stimulation of the vagus nerve. Since this nerve runs through the diaphragm, belly-breathing techniques—like the ones we wrote about here and the recent breathing blog—are a powerful way to increase PNS activity.

Gentle movement, like practicing tai chi, taking a yoga class, walking 10,000 steps a day or spending the day on household chores, is another fantastic way to support ANS balance. (Who knew housecleaning day was good for your health?) Low-intensity interval movement like this helps improve the circulation of blood and lymph, clearing away waste from our cells and supporting the body as it recovers from stress.   

Sympathetic stimulating activities

If health is about balance, then it can’t be all about relaxation. Besides, who can really relax before a job interview, or their wedding, or a big game? As one expert puts it, “get amped and don’t screw up  is a great mindset strategy for handling nerves.

Because ANS activity is linked to our eyes, eye-activation exercises can be a great way to stimulate the sympathetic nervous system. In fact, NHL goalkeeper Connor Hellebuyck does a (fairly involved) series of eye exercises as part of his pregame ritual. Try these next time you need to amp up your readiness!

1. Near/Far Activation: Head outside and pick something to look at that’s far away but close enough to see clearly. Then hold a thumb up in front of your face at arm’s length. Focus on the thumb for a moment, then shift your focus to the farther-away object for a moment. Switch back and forth 10 to 15 times.

2. Moving Thumb: Hold a thumbs-up position out at arm’s length in front of you. In this exercise, you want to keep your head still and follow your thumbnail with your eyes only. Slowly rotate your thumb from the up position to the side and then to a thumbs-down position and back to the start. Do this 10 to 15 times, gradually increasing the speed of rotation, as needed.

3. Moving Body: From a standing position, pick a point on the wall across the room from you. Stare at that point as you move a few steps to the left, then to the right and back to center while keeping your head still, letting your eyes move to maintain focus on the point on the wall. Repeat this five to 10 times. You also can start this exercise in a chair and change position to standing and then to squatting down.

Photo credit: solvod, Thinkstock; Hermes Rivera, Unsplash; curtis_creative, Thinkstock; Tom Sodoge, Unsplash; ulza, Adobe Stock


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Sarah Casey

Sarah Casey is a writer whose work with Institute of Motion (IoM) helps readers cut through health industry jargon and advice. At IoM, Casey investigates ideas and strategies outside of the fitness/health sphere, to discover new methods to support preventative health initiatives. She’s currently exploring how high-value interactions can improve preventative health education and technology. Casey lives with her husband and two daughters near the beautiful Great Lakes and enjoys vegetable gardening and swimming in the summer, snow shovelling and ice-skating in the winter, and a good mystery novel any day of the year.


Michol Dalcourt

Michol Dalcourt is an internationally recognized expert in human movement and performance. He is the Founder and CEO of the Institute of Motion, inventor of ViPR and Co-Founder of PTA Global. Dalcourt has done extensive work and field research in the area of human performance. He consults with many of the fitness industry’s biggest companies and his highly innovative techniques have been adopted by many of the top international fitness certification bodies.