When you see someone perform Eka Pada Rajakapotasana IV, you're witnessing many hours of practice and refinement of other poses to prepare for this one. The pose requires deep hip and spinal extension, supple shoulders, and a steady core. Barbara Benagh created this sequence to prepare your body for this master pose.
Read the full article from YJ's May 2010 issue: Bird by Bird
For a collection of 5 Master Class practices check out Yoga Journal's Advance Your Practice DVD.