Physical and Therapeutic Benefits of pose

This pose has been nicknamed the "King of Poses" because it is hailed for the many benefits it presents.

Physically the pose helps to stimulate blood flow to the brain. This helps with clarity of thought and reflexes due to increased oxygen in the brain. Because this pose is an inversion, it helps to move toxins out of the body by bringing the legs over the heart center. These benefits can only be experienced when breathing is stable and relaxed, so remember to come out of the pose if you experience pain or lightheadedness.

As mentioned above, the increased oxygen helps with clarity of thought and helps to release tension in the mind. This can be a very relaxing pose and changes the practicer's perspective when they are inverted. Even in modifications of the pose, the most important element is having the legs above the heart and brain. In order to experience the clarity of thought, and both physical and mental benefits.

http://www.indovacations.net/Yoga/salamba-sirsasana.htm