Kriya Yoga works by the Pranyama of the practitioner, or the life force is directly controlled. Through the control of life force the Yogi is able to overcome all the obstacles that hinders the union with the divine lord.
Kriya Yoga is the specific Yoga that was revived in modern times by Lahiri Mahasaya in the year of 1861. Paramhansa Yogananda made the Kriya Yoga publicly popular through his book 'Autobiography of a Yogi'. The Kriya Yoga consists of a number of Yogic techniques that are considered to enhance the practitioner's spiritual development and to help to enter into a state of profound tranquility and sense of spirituality.
Paramhansa Yogananda was the master of Kriya Yoga, which was the part of the spiritual path that includes other Yoga practices also. The disciples of Kriya Yoga follow the line shown by the gurus or the spiritual teachers. The Kriya technique is generally taught after about one year of study and practice of the other techniques that are the component of path of Kriya Yoga. Kriya Yoga teachers are called 'acharyas' who teach the technique of Kriya yoga directly.
In Yogananda's own word Kriya Yoga is described as "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."