'Pranayama' regulates the incoming and outgoing flow of breath with retention. It is to be practiced only after attaining perfection in 'asana.' Pranayama is considered the heart of yoga. Usually, the flow of breath is unrestrained and irregular. Observing the variations of breath and conditioning the mind to control the inflow, outflow, and retention of the breath in a regular, rhythmic pattern is 'pranayama.' 'Prana' is an auto-energizing force that creates a magnetic field in the universe and plays with it to maintain and dismantle it for further fabrication. It impregnates each individual as well as the universe at all levels.
It acts as physical and mental energy, where the mind gathers information. It also acts as an intellectual energy with a discriminative faculty where information is examined and filtered. The same 'prana' in different contexts also acts as sexual, spiritual, and cosmic energy. Heat, light, gravity, magnetism, power, vigor, vitality, electricity, life, and spirit are different forms of 'prana.' All that vibrates in the universe is 'prana.' It is the extramundane personality, formidable in all beings and non-beings. It is the principal mover of all activity and the wealth of life.
The self-energizing force in 'Pranayama' is the principle of life, consciousness, and the creation of all beings in the macrocosms. All beings are born through it and live by it. When they die, their breath disintegrates into the cosmic vital force. 'Prana' is the hub of the wheel of life and yoga because everything gets established in it, and a yogic practitioner can get closer to the cosmic energy through 'Pranayama.' It is routed to the genesis of life, bringing the sun's warmth, the moon's gentleness, the beauty of clouds, the power of wind, the amazement of rain, the significance of earth, and all forms of matter into existence. Everything, including the man, takes shade under it. 'Prana' is the fundamental vivacity and the source of all knowledge.
Ayurveda says the human body contains seven constituents and three permeating humors. The seven elements - chyle (rasa), blood (rakta), flesh (mamsa), fat (meda), bones (asthi), marrow (majja), and semen (sukra) sustain the body. They keep the body immune from infection and diseases. The seven elements get churned together in 'pranayama' to produce the nectar of life. The spinal column acts as a whisk to churn the breath to produce energy and stabilize consciousness. And the body becomes the fountain for producing the nectar of life (Amrit), and the lord of the body (parmatma) becomes its generative force.
The generation and distribution of 'prana' in the human body mechanism get compared to the production and functioning of electrical energy. 'Prana' is like the falling water or the rising stream, similar to the energy of falling water or rising steam, which gets to rotate the turbines within a magnetic field to generate electricity. In the human body, the thoracic area is the magnetic field.
The practice of 'pranayama' makes the spindles act as turbines and transmit the drawn-in energy to the remotest cells of the lungs for generating energy. The energy is accumulated in the 'chakras' and gets distributed throughout the body through the transmission lines of the circulatory and nervous systems. 'Pranayama' uses in-drawn energy to maintain the entire human system, comprising the respiratory, circulatory, nervous, digestive, excretory, and reproductive systems, with optimum harmony and efficiency.
In 'pranayama,' the carpet of the mucous membrane of the nostrils filters and cleanses the breath as it enters inhalation. Upon exhalation, sufficient time is given for the system to absorb the in-drawn energy so that the breath may mingle with the blood. The purified blood, filled with chemical properties and hormones, is called a 'constituent full of jewels' or 'the jewel of blood' ("ratna purita dhatu"). Full use of the absorption and re-absorption of energy will allow one to live a hundred years with perfect health of body, clarity of mind, and equipoise of spirit. Henceforth, the effective practice of 'pranayama' is considered to be a great science and art.