The fish comes after the plough in our series and continues the backward/forward pattern of these first asanas (postures).
The fish is an important corrective to slouching and rounded shoulders. Downward pressure on the elbows allows the chest to be thrown completely open, so that with time you will notice that this posture allows you to breathe more deeply than at any other time in your time.
Swami Vishnudevananda saw the posture as a corrective to ‘modern’ posture problems caused by ‘neckties, tightly buttoned shirts’ and ‘foundation garments’. Swami Vishnudevananda, writing in the 1950s in the New Illustrated Book of Yoga:
Owing to improper clothing, our bodily movement is generally restricted to a very limited area, especially the cervical [neck] region of the vertebrae and the shoulder muscles. Neckties, tightly buttoned shirt collars, and poorly cut jackets restrict movements of the cervical [neck] region and stop the free flow of circulation to the upper portion of the body. Women’s tight foundation garments can cause considerable havoc with blood circulation, breathing, and movements of the sacral [base of spine] and lumbar [small of back] region, which can weaken the abdominals. To remove stiffness of the sacral and lumbar regions and shoulder muscles and increase the circulation to these affected parts, Matsyasana or fish pose is invaluable. This also strengthens the thyroid.
The fish is followed by the sitting forward bend.