Nadi is the Sanskrit term for the sacred rivers that conduct prana (life force) throughout the body.
They are the yogic representation of the nervous system. There are 72,000 nadis in the human body. The flow of prana through these channels is what animates the physical body.
One of the purposes of yoga practise is to purify the nadis. When they are bent, blocked or broken our energy can not flow freely. Examples of blockage might include physical or emotional tension stored in the muscles.
One way to work towards this is to concentrate on specific breathing techniques (pranayama) such as alternate nostril breathing (nadi shodhana).
In the classic text on Hatha Yoga “The Hatha Yoga Pradipika” the importance of learning to restrain or control the breath is described:
When the breath is unsteady, the mind is unsteady. When the breath is steady, the mind is steady, and the yogi becomes steady
Another way to work towards free flow in the nadis is to open the channels through the regular practise of physical postures (asana).
There are three main nadis’s in the human body:
Shushumna runs up the spine
Ida starting at the left of the spine and cork screwing up through the left nostril stimulates left brain function, promotes quieter more reflective mood, activates parasympathetic nervous system Qualities: female /passive /moon /night
Pingala starting at the right of the spine and corkscrewing up through the right nostril. Stimulates right brain function, promotes action Qualities: masculine/dynamic/sun/day
When the prana is flowing freely in the nadi’s all three sacred rivers join together at Ajna Chakra, the third eye centre. This is Hatha Yoga- the union of sun and moon.