Description and Benefits
This posture is one of the 4 major inversions, which include handstand (adho mukha vrkasana), forearm stand (pincha mayurasana), headstand (sirsasana), and shoulder stand. Of the four, shoulder stand is the most accessible and the most problematic. Almost anyone can get into it, especially if they use momentum. However, the neck is very vulnerable and therefore this asana needs to be approached with respect and preparation. Esentially, you are standing on the shoulders with the back of the head completing the tripod made by the backs of the arms. The hips eventually (for some) will stack directly over the shoulders with the feet making a vertical line from the hips. The energy is up through the feet rather than sinking into the ground.
If done correctly, the benefits include reversal of gravity’s effects on the circulatory, skeletal, and lymphatic systems and organs. Some say this posture reverses the effects of aging. The thyroid gland, which is housed in the neck, is said to be balanced, creating eveness of metabolism, energy, and toxin removal.
All the muscles that run along the back of the body, especially the muscles around the backs of the shoulders, the upper back, and the neck extensors are strengthened. Therefore, this pose helps to improve posture and spinal alignment. A prerequisite to doing this posture correctly is to be able to clasp the hands behind the back with straight arms and palms together. This combination of strength and flexibility allows for the weight of the body to be supported evenly between the back of the head, upper arms, which are parallel,and backs of the shoulders, with the shoulder blades slightly retracted. The neck should remain in neutral alignment, which means all the cervical vertebrae are off the floor, especially the C7, which is the big weight-bearing one that attaches your neck to the rest of your spine. (Kind of important!)
Suggestions and Modifications
I highly recommend modifying this pose if you have any injury or misalignment in the neck, if you lack the afforementioned flexibility in the shoulders, and/or if you are beyond 3 months pregnant.
Modification #1: Wall assist
Lie on your back with the hips touching the wall and your feet up. Walk up the wall with your feet until you can begin to draw your upper arms and shoulder blades together and place the hands under the hips. This is a great place to test the hands together with straight arms thing (maybe you can do it here). The feet up on the wall allows you to work on the alignment while having the weight of the lower body more supported.
Modification #2: In the middle of the room
You can do a half shoulder stand. In this version you just lift your hips up half way, support them with your hands but keep the upper back on the floor. The legs will end up being angled back instead of straight up and down.
Modification #3: In the middle of the room or on the wall
Tuck your hands or a block under your hips and bring the legs straight up in the air. This is the most modified and the best for neck injury and late pregnancy.
Essentially you are doing maha or tri bandha (all three locks engaged at once, mula ,jalandhara, and uddiana bandha). The head and neck are in jalandhara. This tri lock is said to increase the experience of pratyahara, sense withdrawal, which is the fifth limb of astanga yoga. In essense it allows for prana to stay in instead of flowing out. Interestingly, this asana also is said to balance the 5th chakra, that is, the throat chakra. The throat chakra, when balanced, manifests as honestly speaking your truth and living consistently with your ethics. Shoulder stand falls into the cooling or grounding category, partially because of the maha bandha discussed above but also because of the strong connection between the head and the ground. This is why you will see it in the traditional closing sequence of astanga yoga.
I like the posture because of the sense of lifting upwards and lengthing the spine while still having the ability to watch and hear the breath. I definitely feel my heart rate and breath rate slow down. If you are uncomfortable in the posture, however, it will have the opposite effect! Make sure that you find a modification that allows you to breathe fully without any discomfort.
Often you will see fish pose (matsyasana) after shoulder stand. Fish incorporates extension of the neck and spine. The neck extension is a direct counter to shoulderstand, while the spinal extension is a counter for the poses that often accompany shoulder stand, such as plow.