Samurai mastered breathing techniques to lower their heart rate and remain calm during battle.

The practice of controlled breathing in Japanese martial arts is often referred to as 'Kokyu-ho' or 'Ibuki.' These techniques focus on deep diaphragmatic breathing to stimulate the vagus nerve, which is the primary component of the parasympathetic nervous system. When the vagus nerve is activated, it releases acetylcholine, a neurotransmitter that naturally slows the heart rate and induces a state of 'mushin' or 'no-mind.'Historical accounts and modern physiological studies suggest that trained warriors could maintain a resting heart rate of approximately 40 to 50 beats per minute even under extreme stress. In contrast, an untrained individual's heart rate typically spikes to 120–180 beats per minute during a life-threatening confrontation. At these high rates, fine motor skills deteriorate and tunnel vision sets in, making precise swordplay nearly impossible.Research conducted by institutions like the HeartMath Institute has validated these ancient methods, showing that rhythmic breathing creates 'cardiac coherence.' This state synchronizes the heart, lungs, and brain to improve decision-making and reaction times. Today, these exact principles are taught to Navy SEALs through 'box breathing' and to Olympic athletes to manage performance anxiety and maintain peak physical efficiency.