The practitioner of Hatha Yoga looks at the body as the basis for further spiritual realization and thus, the intensive effort to make it stable, strong and energetic is intended to provide a true platform for spiritual development. A body that is weak, sick, tired or worn out is unable to sustain the concentration of conscious force (tapasya) needed to attain any kind of realization of a consciousness beyond the normal boundaries.
Sri Aurobindo explores the science of Hatha Yoga from this view: “The body, thus liberated from itself, purified from many of its disorders and irregularities, becomes, partly by Asana, completely by combined Asana and Pranayama, a perfected instrument. It is freed from its ready liability to fatigue; it acquires an immense power of health; its tendencies of decay, age and death are arrested.”
Youthful energy, extended life span and vigour are a few of the additional qualities that can ensue from the intensive practice of Hatha Yoga. The Hatha Yogin recognizes that the process of spiritual perfection requires long and patient effort, and the process of dying, and being once again born, and having to re-create the effort after a long period of growth and development of the instrument, is truly a burdensome effort–far better, therefore, if it were to become possible to lengthen the life and health sufficiently to allow far more progress, or even a full realization in the present lifetime!
Sri Aurobindo observes that the wide variety of Asanas, in many cases, quite complex and difficult to master, are able to re-route and regulate the energy flow within the physical system and “…it serves also to alter the relation of the physical energy in the body to the earth energy with which it is related.” Through these means the outer gross body becomes more refined and takes on more qualities of the subtle body, and physical effects, including the possibility of levitation may ensue. This is the basis by which certain special powers begin to manifest for the dedicated Hathayogin. “Moreover, the life ceases to be entirely dependent on the action of the physical organs and functionings, such as the heart-beats and the breathing. These can in the end be suspended without cessation of or lesion to the life.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 27, Hathayoga, pg. 511