Nestor's exploration of breathing is eye-opening and occasionally mind-blowing. The book weaves between the author's personal experiments (including deliberately obstructing his nasal passages for 10 days), historical breathing practices from cultures worldwide, and cutting-edge scientific research.
What makes this book compelling is the simplicity of its central insight: something we do 25,000 times per day—breathing—may be fundamentally broken for many modern humans. Nestor argues that mouth breathing, rapid shallow breaths, and other modern habits might be connected to numerous health problems: sleep apnea, anxiety, hypertension, poor posture.
The practical takeaways are simple:
- **Breathe through your nose**, not your mouth
- **Slow down**: 5.5-second inhale, 5.5-second exhale (about 5.5 breaths per minute)
- **Exhale fully**—most people don't
Critics on Goodreads (4.14 stars, 114K ratings) flag legitimate concerns: "lacks rigorous scientific methodology," "4 parts good info and 1 part crackpot," "minimal footnotes; bibliography only on website," and "New Age spiritual elements late in book." The critique is fair—Nestor oversells some claims and the later chapters wander into speculation.
But the strength of the work lies in how it balances skepticism with openness. Nestor documents seemingly miraculous results from breathing practices while consulting with scientists and medical professionals. The core claims about nasal breathing are well-documented; the more exotic claims warrant skepticism.
While some chapters warrant further research, the book makes a convincing case that breathing deserves far more attention than it typically receives. The techniques are free and immediately testable. Try the 5.5-second rhythm now—you might feel the difference.
For Nestor's other work on human limits, read *Deep*—his exploration of freediving and the ocean. For another frontier of human physiology, try Pollan's *How to Change Your Mind* on psychedelics.