The Science of Why Yoga Quiets the Mind

The secret is in slow breathing and the regulation of the nervous system.

“woman standing beside body of water” by FERESHTEH AZADI on Unsplash

I have been practicing yoga for a decade, but it took an unexplained injury to push me towards a daily practice

I had spent a brutally cold winter battling sciatic pain in my legs, which doctors eventually chalked up to “muscle tension.” For years, as a professor my days were spent at a desk chair, slouched over a computer. I always prided myself on staying in shape, taking breaks to run or lift weights.

But now it seemed the years of sitting at a computer had taken their toll. I switched to a standing desk which helped considerably. But it was yoga that made the difference.

As I recovered, I carefully worked my way back to an hour-long yoga practice. After a few weeks of practicing each morning, I noticed that time had seemed to slow down in my life, enabling me to live in the present rather than worry about the future.

I was more skilled at recognizing how unrealistic expectations or unfounded worries created stress. My posture, sleep, and mood improved. I felt happier and more at ease.

Inspired by my experience, I started reviewing scientific studies about yoga, digging deep into what researchers were uncovering about its mysteries.

In the coming months, I will be sharing what I discovered and continue to learn. I will be drawing on books and studies I have found useful, interviews with yoga instructors and practitioners, and visits to yoga studios across cities.

It’s about the breath

Even though more than a 1,000 studies have been published on yoga, only a few gold standard studies exist. A main reason is a lack of funding, which limits well-designed clinical trials to just a few dozen subjects.

But based on available evidence that lines up with what we know about the body, the brain, and the nervous system there are a few things we can at least hypothesize about why yoga makes us feel so good.

Yoga as a form of exercise releases endorphins, which are thought to create not only temporary forms of euphoria, but also can help mask pain. Yoga similarly lowers cortisol, a hormone correlated with stress, depression, and anxiety. By regulating cortisol levels, yoga may help practitioners produce more melatonin, which can improve sleep and thereby overall mood.

Fast breathing like when running increases oxygen in our bloodstream. In contrast, the slow breathing of yoga increases carbon dioxide levels. In response, blood vessels in the brain dilate, sending more oxygen to the brain.

But compared to running or lifting weights, it’s yoga’s focus on controlled breathing that makes the practice unique, writes William J. Broad in 2012’s The Science of Yoga.

Almost all forms of yoga emphasize Ujjayi pranayama, a style of slow breathing.

Fast breathing like when running increases oxygen in our bloodstream. In contrast, the slow breathing of yoga increases carbon dioxide levels.

In response, blood vessels in the brain dilate, sending more oxygen to the brain. By enabling our brains to absorb more oxygen, the slow breathing of yoga increases calmness and alertness, writes Broad.

Just flow

But a focus on the breath also has other benefits.

Practicing Ujjayi breathing involves constricting the upper larynx by partially closing it with the part of the throat we close when we drink water, producing a slight hissing sound, explains Gregor Maehle in 2006’s Ashtanga Yoga: Practice & Philosophy.

Listening to the sound of our breath during our practice, draws our attention inward, “withdrawing our senses from the outside world.”

As we become more familiar and comfortable with different poses, we can start to use the musculoskeletal system to create different forms with the body, much like an “artist would use a brush or chisel to create a work of art”…

Our breathing also helps us observe our mood.

Our breath, explains Maehle, may at times sound aggressive, tired, strained, or fast. By drawing our attention back to a smooth, pleasant sounding breath, we can start to recognize negative emotions or thoughts.

Yoga can also be a way to exercise the right side of our brains, argues the orthopedic surgeon Ray Long in his illustrated book The Key Poses of Yoga.

As we become more familiar and comfortable with different poses, we can start to use the musculoskeletal system to create different forms with the body, much like an “artist would use a brush or chisel to create a work of art,” writes Long. “This results in a cognitive shift to visual right brain thinking and evokes a trance-like meditative state.”

Cycling through

A third way that yoga is unique from other forms of exercise, writes Broad, is yoga’s ability to regulate autonomic features of our nervous system, functions that were once considered beyond our reach to control.

Studies show that yoga has the unique ability to either put the brake on our sympathetic system which generates “flight or flight” stress reactions, or boost our parasympathetic system which controls our “rest-and-digest” functions.

By cycling through the fast and slow parts of our nervous system, a yoga practice gives our metabolism and nervous system a healthy workout, promoting greater balance.

A typical hour-long yoga practice will cycle through braking the sympathetic system and boosting the parasympathetic system.

Fast flowing Asanas such as those that start an Ashtanga practice stimulate our sympathetic system. More static poses that we hold for a longer period of time or in positions of relaxation put the brake on the “fight or flight” system and promote the “rest and digest” parasympathetic system.

By cycling through the fast and slow parts of our nervous system, a yoga practice gives our metabolism and nervous system a healthy workout, promoting greater balance.

In other words, writes Broad, yoga seems to not only promote the body’s flexibility, but also our inner flexibility, allowing us to more easily sink into a state of quietude and letting go.

See also:

Instead of Practicing Yoga as a Workout, Focus on the True Benefits

Scholars Trace the Impact of Jon Kabat-Zinn on America’s Mindfulness Movement