The Flow of Prana
The foundation of all life, of the whole universe, is the subtle life force energy that yogis call "prana." This mystical energy flows through our bodies and generates our every action – from gross physical movements to minute biochemical processes.
Prana comes into the body from the food we eat, the air we breathe, and from absorbing the energies of the earth and heavens. Prana travels through thousands of tiny channels called nadis to every cell in the body. The three main nadis in the body are the ida, pingala and sushumna, which all start at the base of the spine and travel upwards to the head. The ida and pingala nadis crisscross each other as they spiral upwards and connect to opposite nostrils, while the sushumna travels straight up the spine to the crown of the head. The chakras are located where the ida and pingala cross each other and intersect with the sushumna. The chakras connect with the thousands of minor nadis and are thus responsible for the distribution and circulation of prana throughout the whole body.
Normally, prana is restricted from flowing through the sushumna by locks above each chakra. These locks primarily function to stop the activation and flow of kundalini, the transcending potential energy coiled at the base of the spine, from entering the sushumna and rising to the crown chakra.
Hatha yoga was developed to circulate, cultivate, and control prana, and to activate and channel kundalini up the sushumna nadi to the crown chakra. Asana cultivates and circulates prana in the body and strengthens the nadis. Pranayama, the use of various breathing techniques, controls and cultivates the prana and purifies the nadis. Bandhas are energetic locks that contain the prana in the torso and concentrate it in the three main nadis. Mudras regulate and channel prana into the chakras and arouse the kundalini prana. By cultivating, controlling, and activating prana and kundalini, hatha yoga aims to liberate the mind and expand consciousness.