For most of us, the concept of “breath control” is silly. I mean, like, I’ve been doing it naturally since I was, like zero years old … now you’re telling me I should work to control my breath? Yep.
Here’s an amazing physiological feat that your breath performs:
Respiratory sinus arrhythmia (RSA) is a naturally occurring variation in heart rate that occurs during a breathing cycle. Heart rate increases during inhalation and decreases during exhalation.
Heart rate is normally controlled by centers in the medulla oblongata. One of these centers, the nucleus ambiguus, increases parasympathetic nervous system input to the heart via the vagus nerve. The vagus nerve decreases heart rate by decreasing the rate of SA node firing. Upon expiration the cells in the nucleus ambiguus are activated and heart rate is slowed down. In contrast, inspiration triggers inhibitory signals to the nucleus ambiguus and consequently the vagus nerve remains unstimulated.
Adults in excellent cardiovascular health, such as endurance runners, swimmers, and bicyclists, are also likely to have a pronounced RSA. Meditation and relaxed breathing techniques can temporarily induce RSA. RSA becomes less prominent with age, diabetes and cardiovascular disease.
This is just obscure science-talk for the notion that slowing down and extending the breath is a good thing – good because increasing the length of one’s exhalation stimulates the vagus nerve which has wonderful effects on a person’s heart rate (slowing it), immune system, and sense of well-being (e.g., in 2005, the Food and Drug Adminsitration approved vagus nerve stimulation for the treatment of depression).
Yoga practitioners use something called ujjayi breathing wherein they constrict the back of the throat, which allows the breath to flow more slowly and evenly. This tends to increase Respiratory Sinus Arrhythmia and its concomitant health benefits.
As Richard Freeman so eloquently describes in the video below, breath control is the heart, soul and root of yoga practice.