This is what we call one of the “anti-gravity” postures. Studies show that gravity is the single most powerful physical stress on the body. In this case, instead of hanging upside down, we’re using the back and shoulder muscles to elongate and decompress, and counter the effects of gravity on your spine. This is a great pose to do anytime you have been seated in your car or at a desk for extended periods of time (30 minutes or more).
This is a very basic, but very beneficial pose. I recommend that you do not lean too far back – no more than a 45-degree angle – to the vertical standing position. When you reach up to the sky, also be sure that your heals are firmly grounded. Your feet should also be slightly webbed at the toes.