The word matsya in Sanskrit means fish. The body resembles fish in this posture.
Lie down on your back. Then go into Padmasana while lying down. Let knees remain on the ground. Raise your head making an arc with chest. In this position a sort of bridge will be created between your head and waist. Grasp the toes of your feet with hands. Leave toes put your elbows on ground and with their support raise upper portion of body. Staying in this position move your neck from left to right clockwise and anti-clockwise.
This asana relieves the stiffness caused in neck. It invigorates pituitary glands. The neck, face, lungs and heart get nourishment. Muscles of waist and abdomen get proper exercise and constipation is relieved.