“Ninja” Respiration Management:

Medical Explanations from the Viewpoint of Anesthesiologists

Abstract

　　In medieval Japan, special operation agents known as “Ninjas” had a profound interest in the management of respiration for successful completion of their mission as well as for their own survival. Examples of their knowledge regarding respiration include being able to estimate the depth of sleep by recognizing the difference between rapid-eye-movement (REM) and non-REM sleep, suppressing their own breathing sounds, adapting special breathing techniques for long distance running, and fostering mental stability through the use of unique breathing patterns. The classic literature notes that ninjas used special breathing apparatuses that allowed them to remain underwater for long durations. For the purposes of the present review, the practicality of these ninja snorkels was investigated in a simple experiment. The findings suggest that the extensive knowledge ninjas held about human respiration was practical and scientifically explainable from the perspective of modern medical science.