Bridge :: Sethu Bandhasana
Moving into and out of this pose helps develop strength in the abdomen and lower back muscles and improves suppleness of the spine and wrists. The knees remain directly above the feet and the buttocks and inner thighs contract to cause the pelvis to lift up without spreading the legs apart. The body forms a bridge as the spine goes into extension.
More advanced yogis may lower themselves into this pose from the shoulder stand. That requires a lot of strength and flexibility in the back. An alternative is to lift up into this pose from the ground.
There are two things of note going on here. One, is that the shoulders should be INTERNALLY rotated in the shoulders. A common error is to externally rotate. Another common error is flexing the wrists. Notice that my wrists are straight, my palms are pressed together and my fingers are interdigitated.
My elbows don't touch the ground because of the size of my triceps and the shape of my elbow joint.
Another very important and less obvious thing to note is that the weight of my upper body is not in my neck or my head, but rather on my upper back and the rear aspect of my shoulders. Please avoid allowing any of your body weight to go into your head or neck for the safety of your cervical spine.
This pose will really compress the thyroid gland. Some pressing of this gland is good as it will stimulate fresh blood into the area.