For thousands of years, Taoist Masters from Wu Dang, the birthplace of Tai Chi, have developed fundamental exercises to build internal strength through Qi Gong. Yang Sheng focuses on the most fundamental "pre-heaven Qi" and replenishes it.  This is the energy one is born with that is depleted by life's stress and illness.  In China they say "living without 'pre-heaven' Qi is like cooking without rice."  These exercises are directed toward building up one's bank of energy.  It is like making an "elixir of life."  In China this is called "Immortality Training."