Man does not live by bread alone and our food sheath, the annamaya kosha, is not all there is. Beneath the outermost sheath is the pranamaya kosha: the energy body. Our journey now takes us beneath our physical manifestation so we can investigate the vital energies of the body and learn how yoga affects these energies.
In the East we find many metaphors and concepts concerning energy. Many yoga texts teach us about prana in its various forms. Many scholars believe that the knowledge of yoga and prana filtered into China over 2,500 years ago. Once there, the Chinese built upon the spiritual uses of these sciences and developed a more complete physiological understanding. In the Daoist explorations, prana became known as Chi  and it has many different manifestations. In the West, scientists and doctors had little time for the metaphysical aspects of Eastern energy. But even in the West, there are various interpretations of the word “energy.” There is the energy of our nervous system that is electrical in form. There is chemical energy transported by our blood system. And, as we will see, there are many other forms of energy now being investigated by Western scientists.
We will look more closely at the three major ways of exploring energy beginning with the most ancient philosophy of India, then the Daoist view, and then the evolving Western understanding. Finally, we will look at how we can measure this energy flow using modern instruments. In the second half of our journey, when we visit The Practice of Yin Yoga we will come back to this investigation and discover the various ways to stimulate the flow of energy.