The 5th asana of the 12 basic positions of the yoga Vidya is the fish (Matsyasana). It helps to relax the shoulders and the back muscles, strengthens the upper back, stretches the chest and acts activating and opening.
I lay on a mat on my back and place my hands under my thighs. During the next inhaling I lift my chest upwards as high as possible and lower my head down backwards. I hold the position for a few deep breaths and go back into the starting position.