Swami Vivekananda
The most obvious manifestation of this Prana in the human body is the motion of the lungs. If that stops, the body will stop; all the other manifestations of force in the body will immediately stop, if this is stopped.
The most obvious of all motions in the body is the motion of the lungs, the flywheel which is setting all the other forces in motion. Pranayama really means controlling this motion of the lungs, and this motion is associated with the breath. Not that breath is producing it; on the contrary it is producing breath. This motion draws the air by pump action. The Prana is moving the lungs, and that motion of the lungs draws in the air.
So Pranayama is not breathing, but controlling that muscular power which moves the lungs, and that muscular power which is going out through the nerves to the muscles, from them to the lungs,making them move in a certain manner, in the Prana, which we have to control in the practice of Pranayama.
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