Benefits
"The abdominal organs are toned by being contracted on one side and stretched on the other.  Due to the lateral twist of the spine, backaches, lumbago and pain in the hip joints disappear rapidly.  The neck muscles become more powerful and the shoulder movements become easier.  The prostate and bladder do not become hypertrophied if one practices this asana regularly.  It helps one to achieve Paripurna Matsyendrasana, where the spine is given the maximum lateral twist." Light On Yoga by B.K.S. Iyengar