The three principal nadis of the energetic body are the ida, pingala and sushumna. These nadis originate in the muladhara (root) chakra and travel up the spine. Ida and pingala are mirror images of each other. The ida nadi is known as the left channel because it flows to the left as it leaves the root chakra and runs to the left nostril. Pingala flows to the right, from chakra to nostril. Sushumna is the center channel and it travels straight up the spine through the center of all the chakras.
Ida nadi controls all mental processes as it transports prana to the nervous system, which calms the mind and relaxes the body. It is associated with introversion, feminine energy, the right (creative) side of the brain, and the left side of the body. Ida nadi energy must be balanced by the pingala energy, which is linear and logical. A major focus of Hatha yoga is balancing these nadis. For example, someone with a free-flowing ida nadi who has a blocked pingala nadi may be nurturing, but might lack the vigor to reach their potential in earthly or spiritual development.
One of the most effective ways of balancing the nadis in yoga practice is through a form of pranayama called nadi shodhana, or alternate nostril breathing. With the fingers of one hand, the nostrils are alternately closed off while the practitioner competes one cycle of a breath in and out through the open nostril.