The Kriya yoga system consists of a number of levels of pranayama, mantra, and mudra based on techniques intended to rapidly accelerate spiritual development and engender a profound state of tranquility and God-communion. The process of performing Kriya Yoga is claimed to lead to a certain purification of the blood which frees up the life force to withdraw into the spine. Kriya Yoga is a simple, psycho-physiological method by which the human blood is decarbonized and recharged with oxygen. The atoms of this extra oxygen are transmuted into life current to rejuvenate the brain and spinal centers.
Kriya Yoga is described by its practitioners as the ancient Yoga system revived in modern times by Mahavatar Babaji through his disciple Lahiri Mahasaya, c. 1861. Kriya Yoga was brought to international awareness by Paramahansa Yogananda's book Autobiography of a Yogi and through Yogananda's introductions of the practice to the west from 1920. Kriya Yoga is the "Yoga of Action".
As Yogananda describes Kriya Yoga, "The Kriya Yogi mentally directs his life energy to revolve, upward and downward, around the six spinal centers (medullary, cervical, dorsal, lumbar, sacral, and coccygeal plexuses) which correspond to the twelve astral signs of the zodiac, the symbolic Cosmic Man. One half-minute of revolution of energy around the sensitive spinal cord of man effects subtle progress in his evolution; that half-minute of Kriya equals one year of natural spiritual unfoldment."
According to Yogananda, Kriya Yoga was well known in ancient India, but was eventually lost, due to "priestly secrecy and man’s indifference". Yogananda says that Krishna refers to Kriya Yoga in the Bhagavad Gita: "Offering inhaling breath into the outgoing breath, and offering the outgoing breath into the inhaling breath, the yogi neutralizes both these breaths; he thus releases the life force from the heart and brings it under his control."
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