Breath by James Nestor is an interesting book subtitled The New Science of a Lost Art. I came across Nestor from his book Free Divers and in this work he delves into the importance of breathing correctly, with his personal experience of how breathing incorrectly can impact health and how to do it better.
Breath through the nose - Nestor details the harm that came to his body from ten days of only mouth breathing, and then recovery after he switched to breathing in primarily through the nose. Problems stemming from mouth breathing include: sleep apnea, snoring, hypertension, cavities, periodontal disease, and bad breath. The book covers how many people have some form of breathing difficulty or resistance and focusing on breathing in through the nose can alleviate that. The nose cleans, heats, and moistens air for easier absorption. Nestor notes how forcing nose breathing at night can be accomplished by something as simple as a postage-sized piece of cloth medical tape over the center of the mouth.
Build lung capacity – Along with how we breath in air, the book covers the importance of building lung capacity, through both physical exercise and breathing exercises. A slow and full exhalation of air is important as we need to get stale air out, and big, heavy breaths deplete our bodies of carbon dioxide, something beneficial to us in balance with oxygen. Slower, longer breaths is noted as what should be done, with Nestor extolling the benefits of breathing in through the nose for 5.5 seconds and out (can be through the mouth) for 5.5 seconds, totaling up to 5.5 breaths a minute. Doing this as a daily breath practice is described as a sort meditation for people who don’t want to meditate, and something that can be developed into a breathing habit.
Breath less – Nestor covers how hypoventilation training, breathing less, something that's been done by world class athletes back to Czech running star Emil Zatopek in the 1950s. Exhaling very long breaths, trying to keep the lungs roughly half full, trains them to do more with less. Also, this helps maintain that balance of carbon dioxide to oxygen, and can be an effective thing to do for people suffering from respiratory diseases.
Chew more – It’s detailed how in prehistoric times, people breathed better, in part because their brains were less developed so the sinus cavities more developed. Additionally, they subsisted on a raw diet that required much more chewing, which developed the jaw, allowing full breath. As people evolved, nasal congestion became more prevalent due to small sinuses, a lack of space through which to breathe. Nestor covers how something as simple as chewing gum (he notes the hard sugar-free gum Falim) can help develop the jaw. This along with breathing exercises can help alleviate nasal congestion and make breathing easier.
Try advanced techniques – Nestor covers Breathing+ techniques like Tummo or over breathing, exhaling all your air out, then holding the breath, to jump-start how you breathe.
There’s a number of interesting ideas in the book, with perhaps the most basic and effective that of breathing in (very importantly, through the nose) for 5.5 seconds and out 5.5 seconds, totaling up to 5.5 breaths a minute.