The physical aspect is the sum total of energy. Energy can neither be created nor destroyed. It's form can change to another, but it will not disappear, because "It" remains constant. The deeper aspects of the Upanishad, this energy in all human beings is inactive. The process of sadhana, understanding and imbibing the Vedas is when this energy is awakened.
The historian N. Bhattacharyya provides a working definition of the benefits of sdhan as follows:
... religious sdhan, which both prevents an excess of worldliness and molds the mind and disposition (bhva) into a form which develops the knowledge of dispassion and non-attachment. Sdhan is a means whereby bondage becomes liberation.
Iyengar in his English translation of and commentary to the Yoga Sutras of Patanjali defines sdhan in relation to abhysa and kriy:
Sdhan is a discipline undertaken in the pursuit of a goal. Abhysa is repeated practice performed with observation and reflection. Kriy, or action, also implies perfect execution with study and investigati ...more