Ardha chandrasana
Half Moon Pose, Ardha Chandrasana
Ardha means half and chandra means moon. From Triangle, the weight shifts onto the front foot and the back leg lifts to hip height, so the body balances in one flat plane with the top arm reaching to the ceiling, exactly as shown here.
It strengthens the standing leg and ankle and trains balance. Most people find it easier with a block under the lower hand and the gaze down at the floor at first, turning the head up only once the hips feel steady.
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