Matsyasana or fish pose is often times sequenced in the cool down portion of a vinyasa flow class. Matsyasana is a very intricate and deep asana that requires a great deal of preparation to fully open the heart to full potential. Once the heart is open the head can be placed on the floor to line up with Sarasrara or the Crown Chakra. When properly aligned, the head and neck are light. If your core is capable, the legs and arms can be extended to create a challenging back bend and strengthener. Staying for several breathes is a challenge for any yogi.
The benefits to Maysyasana are many. With the throat exposed Vishudha is opened and this is where many get stuck. You can not muscle your way through a chakra and this one is a doozie. Vishudha represents not only our communication but rather a deeper truth that comes from our lips and hearts. This truth is a compilation of the other chakras and if the lower chakras are substantially out of alignment, then obtaining full expression in Matsyasana will never happen, despite your dedication to its perfection; as you are not living your truth = vishudha. If your trapped in Svadishtana (most are) then you are unable to see past your ego and selfish desires to ever comprehend Vishudha and what it means to not only speak your truth but live your truth as well.
Physically, Matsyasana is great for increasing oxygen to the lungs, thus is a great asana for anyone with bronchial issues. Vishudha is not the only thing that opens but also the throat that governs it by stretching the pineal, pituitary, thyroid and parathyroid glands. This will awaken the endocrine system, and stimulate the metabolism. The increased oxygen to the neck and face prove beneficial for acne and other skin and throat conditions. It will strengthen back and gluteals and reduce stress and inflammation.