If you hold your arm overhead for several minutes the blood will drain from your fingers, hand and forearm into the upper arm and shoulder. Gradually, your arm will become numb. To a lesser degree this is what can occur when your body is held continually in an upright or a sloping position. Gravity is always at work upon your body exerting its pull on many vital organs and glands and causing the blood to flow in a predominantly downward direction. Since most of our daily activities require that we sit and stand in upright positions you can appreciate the efficacy of inverting the body for a brief interval each day.
Inversion is accomplished in our Yoga study through such postures as the Head Stand, Shoulder Stand, Plough, Chest Expansion and others. These exercises have had a marked effect on the blood circulation of many of my students. For example, the thyroid gland, located in the throat area, secretes into the bloodstream a vital substance that regulates weight, promotes the health of the sexual glands and is responsible for the smooth tempo of many important body functions. People who suffer from over-active or under-active thyroids are deficient in the timing of their activities as well as in their metabolic processes. The Shoulder Stand helps to promote the correct functioning of the thyroid by bringing an increased supply of blood into the throat area. Hence the great value of this posture. The Head Stand has been responsible for improvement in hearing and vision as well as for added beauty of the hair and complexion. One of the finest, natural ways to restore and maintain alertness is to allow an increased supply of blood to flow into the brain. Thousands of professional people throughout the world are aware of this and many practice the Head Stand for up to 15 minutes each day! It is also important to note that the Yogi regards the Head Stand ( Sirshasana ) as the major posture to increase the capacity and power of the brain. I always advise students who have had a history of illness with regard to circulation, heart, brain or other organs and glands to obtain their physician’s approval before attempting any of the inverted postures.
To summarize: The heart is always pump ig against gravity to circulate the blood into the vital organs and glands situated above it. With the body in the inverted positions those organs and glands are now below the heart. The effect of this simple maneuver on the entire organism is truly remarkable.