Kundalini 
Kundalini noun  (Sanskrit derived from the root  kunda-, a coiled-up serpent, and  -ini power.)
: the yogic life force that is believed to lie coiled at the base of the spine. Used in this connection first  in 1897.
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Kundalini is the energy that sits dormant in the first chakra at the base of the etheric spine. This energy is released during orgasm through the second chakra, as the body attempts to create a child. Also during life-threatening situations, the kundalini energy may be released. This is how people suddenly have the superhuman strength to save themselves or a loved-one. Most of us have heard about the grandmother who had to lift a car to save her grandchild. Her kundalini was released, giving her the power to do what she needed to do. Long ago, some yogis discovered that the kundalini can be used to move very quickly into higher states of consciousness. It is through the energy of  the chakras, that the kundalini is activated and begins to rise.

      The kundalini is coiled up like a very tight spring, and when released there is sometimes an explosion of power. Properly directed, the kundalini will travel up a tube in the energy body that lies close to the spine. Without proper direction, the release of kundalini can be very uncomfortable and possibly damaging. (This is why it is very important to study kundalini yoga with an experienced guide.)

     On it's way up, the kundalini both cleans and strengthens the energy body and chakras. You may feel a warm sensation moving up  your back.   If your head feels like it's burning,  you may be pushing too hard, too fast.

      Be sure to consult with your teacher.You could think of kundalini yoga as a way of tapping into a natural storage of power that we all have to fuel your practice. Like the gasoline you put in your car, kundalini by itself is relatively harmless but when combined with will power, it can become volatile if not handled with respect

 
The 
caduceus 
symbol of coiling snakes
is thought to be an ancient symbolic
representation of Kundalini physiology

     This is the dominant spiritual energy in all human beings and it is destined to be awakened. After awakening, this energy is the dynamic force behind meditation. It is an elemental, creative force of the astral body which, like a serpent, rests coiled at the base of the spine. The male and female forces are represented in the balanced Ida and Pingala subtle channels. Everyone uses Kundalini power to think with and to maintain consciousness, but it very seldom rises up the central spinal channel of Sushumna beyond the first center. Various disciplines areused to  arouse the "sleeping serpent" to ascend to the higher centers.