As per. "The Aquarian Teacher" (Bhajan):

"This exercise opens the lungs, brings the hemispheres of the brain to a state of alertness and consolidates the magnetic field, stimulates and stretches the lower and mid-spine, helps elimination, stretches the sciatic nerve and brings circulation to the upper torso. Develops flexibility of the lower spine and sacrum and charges the magnetic field. Balances the sexual energy and draws the prana to balance apana so that the Kundalini energy can circulate to the higher centers in the following exercises. Sat Kriya circulates the Kundalini energy through the cycle of the chakras, aids in digestion and strengthens the nervous system."