Bhujangasana, the cobra, is the sixth of the 12 basic postures of hatha yoga. It is also the first of three back-strengthening exercises done as part of a normal yoga class. The main benefits of the cobra are to build strength and flexibility in the back. The resting posture before and after the three back-strengthening exercises is done by laying on the stomach, rather than the back.

Physical Benefits
Builds strength in the muscles of the upper back
Increases flexibility in the lower back
Massages the internal organs, especially the digestive organs
Removes rounded shoulders
Helps relieve menstrual problems
Energetic (Pranic) Benefits
Stimulates swadhisthana and manipura chakras
Mental Benefits
Improves concentration