Cleansing and purification :: Meltdown

Nauli kriyas
If you look around you, you’ll notice what happens as we get
older. The middle of the body begins to lose shape and collapse.
Gravity is pulling us downward. Unless we are practicing some
type of opposing technique, the whole solar plexus area, a major
nerve center of the body, will become squashed. Not to mention
the toxins that get trapped, the poor digestion that results, and the
lack of oxygen to the abdominal region. Naulis, in conjunction
with the bandhas, bring everything upward, inviting vitality back
into the middle of the body. These techniques keep the gastro-intestinal or alimentary system balanced and functioning smoothly. Naulis massage the internal organs, acting as an internal cleansing technique. Keeping you pure and clean, naulis remove sluggishness of the stomach, intestines, and liver, bringing back upward the evercaving-in abdominal
region which is crushing and suffocating internal organs as gravity
pulls us down. Don’t let the fire go out. Keep the channels of the body pure and
open the pathway for the oxygen to keep feeding the fire. It’s best
to practice on an empty stomach in the morning.

from : ashtanga yoga manual