Many body systems naturally use electro-magnetic energy.

Western scientist studying acupunture points have found that those points are strategic condutors of electro-magnetic energy (known as 'qi' in the east).

When these points are stimulated the electro-magnetic signals travel at a much faster rate through your body.

Most probably one of the reasons that stimulating acupuncture points is so effective for pain relief is that this augmented flow of electro-magnetic energy improves your body's production of pain killing substances such as endorphins.