In Sanskrit ardha means "half," and chandra means "moon," thus, this is the "half moon" posture. This pose is also one the postures that are are sequenced in surya-namaskar (the Sun Salutation).
Position of Readiness
Stand in the tada-asana (Stand erect with your heels together and toes apart). keep the back straight and the arms pressed slightly against the sides with palms facing inward.
Raise arms over the head and fold the hands keeping palms together. Keep your head between the arms.
While inhaling slowly raise the arms straight up keeping the palms pressed lightly together.
Arch your body backwards keeping your arms alongside your neck and head, tilt the head backward and hold.
Keep your knees straight while holding posture
Slowly return to the tada-asana.
Repeat the same 2-3 times.
The ardha-chandra-asana is the basic stretching and balancing pose that mainly benefits the lower back, abdomen and chest. This asana makes the rib cage supple and flexible. It massages, loosens and strengthens the waist and brings balance in the body posture.