Hey Wayne, the practice of asanas are to achieve great health and balance of body with its connection to mind and spirit. The Siddhas would correct certain things about their bodies, or achieve certain energetic (pranic) currents through the mastery of asanas.
For example, the asana Siddhanasa, is designed for meditation. Mastery of that asana encourages deep meditations and the raising of kundalini (especially because the ball of the foot is at the perineum).
Kundalini, if you dont know, is the dormant energy at the base of the spine (like a coiled serpent). When one reaches certain states of samadhi (super consciousness) the serpent uncoils and travels up the spine through all of the chakras or (energy/pranic centres) until it passes through the top of the skull.
Part of practicing asanas is helping to align the physical spine and body to a more “perfect” state to allow for a more cohesive conductivity. The chakras are not actually in the spine itself. They are along the pranic path called the sushumna, which is an energetic tube connecting the bottom chakra to the top (base of the spine or coccyx, to the back of the neck or medulla). This energetic tube is influenced by the alignment of our physical spine and vice versa. This is why it is important to sit up straight in meditation.
Now, not only is there a sushmna pathway, but there is also a ida and pingala. These are like right and left channels. One is hot, one is cold. The idea is to balance these. This can be achieved with alum vilanom pranayama (sp?).
And BTW, I must say that Pranayama is a great tool for raising the kundalini, and clearing the nadis. The nadis are your astral nerves, and there are 72,000 of them. Pranayama, and yoga asanas help clear the nadis to increase your spiritual sensitivity.
Think of it this way, if your nadis are clogged, and your life is not balanced, it will be very hard to achieve enlightenment. There are also karmas bound to us which keep us from ascending. It is said that pranayama helps to burn up karmas.
Meditation helps you gain control and insight of your thoughts, so that you can transcend them, and reach samadhi. It all works together. Mastering the mind is by far the most difficult task anyone could do, but it is essential in reaching the deepest states of bliss. There are two main types of meditation, one of them is one pointedness (or unbroken focus on one single thing), or non focus (just being). srry can’t remember the sanskrit names for these.
The whole idea here is awakening to the soul, and unifying into the absolute. The absolute being you know… the universe… god… it is inexplainable (you must experience it, and if you practice you will, and it is amazing, and you will understand how you can’t explain it). And the soul, being your true essence, (just being).
This is the meaning of yoga = “union”.
Anyways… Just remember, lead a balanced life, and practice your sadhana(spiritual practice) regularly(dont stop). The best results are obtained from sticking to it and never quitting. Your sadhana may include: hatha yoga(ie. asanas), meditation, pranayama, and many other things. As you practice these, and study yogic texts, many things will come into place via the siddhis obtained. The siddhis obtained can be very subtle at first, and strong later on, and they can get in the way of the mind being free if one is attached to them, or even attached to getting spiritual results.
So the moral of the story is, don’t get attached to results. Just do! Just practice. Don’t worry about a thing! Relax! Be! But still take action! and Do! Be fully immersed in it by not thinking of the outcome!
Hope that helped! Oh also, read this! google search “sivananda pranayama” and read the free online book, it is awesome! Autobiography of a Yogi is also a great book. I highly recommend it.