Ardha Matsyendrasana - The Half-Spinal Twist Pose

"Ardha" means "half" in Sanskrit. Since the full posture is difficult to be practiced, the half-posture, which is easier, is followed widely. This posture was first promoted by the great Yogi Matsyendranath, one of the founders of Hatha Yoga, and hence the name.
Sequence:

1. Sit erect.
2. Stretch out your legs.
3. Place the right heel in the perineum. Keep the right thigh straight.
4. Place the left foot flat on the floor, crossing the right knee.
5. The left heel should rest close to the right side of the right knee.
6. Pass the right arm over the left side of the left knee and line it up with the left calf.
7. Grasp the left big toe with the index finger, middle finger and thumb of the right hand.
8. Slide the left hand across the small of the back and grasp the root of the right thigh.
9. Turn round your head, neck, shoulders and the whole trunk to the left and bring the chin in line with the left shoulder.
10. Look as far behind you as you can. Keep the head and spine erect.
11. Maintain this position until strain is felt.
12. Release in the reverse order.
13. Repeat on the other side.

Benefits:

* Ardha Matsyendrasana is considered to be the best of the twisting postures as it rotates the spine around its own axis besides giving two side-twists to the spine throughout its length with the greatest efficacy, using one's own arm and knee as a lever.
* As the spine is twisted spirally, each movable vertebra rotates in its socket, as a result of which the spinal column, particularly the lumbar vertebrae, becomes more flexible.