Nadis — The Rivers of Life Force
The 72,000 nadis are the subtle energy channels through which prana flows in the body, the three principal being Ida (lunar, feminine), Pingala (solar, masculine), and Sushumna (central — the channel of liberation).
The Tantric understanding of the subtle body includes 72,000 nadis (channels through which prana flows). The three principal nadis are: Ida (the left channel — cool, lunar, feminine, associated with the right brain and parasympathetic nervous system), Pingala (the right channel — hot, solar, masculine, associated with the left brain and sympathetic nervous system), and Sushumna (the central channel running through the spine from Muladhara to Sahasrara — the channel of spiritual evolution). In ordinary consciousness, prana flows primarily through Ida and Pingala, maintaining the oscillation between activity and rest, masculine and feminine, thinking and feeling. When the two are balanced and prana enters Sushumna, the higher states of consciousness become accessible. Pranayama practices (particularly Nadi Shodhana — alternate nostril breathing) work to balance Ida and Pingala, enabling kundalini to enter Sushumna.
When Ida and Pingala are balanced, prana enters Sushumna — and in that moment, the gate to liberation opens.
The Hatha Yoga Pradipika teaches Nadi Shodhana — alternate-nostril breathing — precisely to balance the lunar Ida and solar Pingala so that prana can enter the central Sushumna.
Hatha Yoga Pradipika