A great source for Yoga Postures by Mark Giubarelli.
Yoga Positions – Padma Bhujangasana
Translation: Lotus in Cobra Pose
From Ardha Padmasana take the other leg up so that you enter full Lotus pose. Lean forward and down placing the hands in front of you. Roll forward and arch the spine in a backbend.
Look forward or up. If you look up this yoga posture it would have Urdhva Mukha in front of its name. This means Upward facing.
Straighten the arms or keep them slightly bent. Straightening them can help reduce the strain in them but the spine must be flexible.
Look forward or up. Looking up can cut circulation off. In yoga it is felt as a pressure that interrupts the flow of water. It may be more beneficial to look forward or do a combination of looking up and then forward. Push into a mild boundary while looking up if you hold this pose for a long time for better blood flow.
Tips One hip has a tendency to raise up a little higher than the other. Make modifications so that a somewhat evenness can be attained in there horizontal alignment.
Force has a tendency to fall on the outside of the hands. This occurs In many of these prone backbends. To correct this raise the pinky finger up and the force will move to the inner part of the hands. Then allow it to return back to the mat and find an evenness with the weight distribution on the palms and fingers.
The Leg adductors are stretched. Some of these are , the pectineus, adductor brevis and adductor longus, the gracilis and adductor magnus. Many of the muscles and ligaments in the knees and ankles are also stretched.
Yoga Teacher Tips
This is a very advanced yoga posture. It can still be taught in class. The best way to approach hard postures while keeping other students happy is to offer postures that are progressively difficult offering those who are less flexible the option of staying in the previous posture while guiding more advanced students further. This way everybody is happy and a multi-level class can be taught.