Central to all the practices of yoga is the movement of prana, the life force or vital energy. Prana is in matter, but it is not matter, it is in air but not oxygen, it is a subtle form of energy that is carried in air, food, water and sunlight, and animates all forms of matter.
Through the practice of asanas and Pranayama, more prana is taken in and stored in the body, bringing great vitality and strength. In addition to the physical body, yogis perceive man as possessing two other bodies that encircles it – the astral body and the causal body. Prana is the vital link between the astral and physical body, but it is mainly in the nadis of the astral body that it flows, as energy, when it is known as ‘apana’.
Prana itself is an afferent impulse, whose nature is to move upward; apana is efferent and moves downward. When the two are united at the Muldhara Chakra, the Kundalini energy awakens.