The Bangles used by women are normally in the wrist part of ones hand and its constant friction increases the blood circulation level.
Also the pulse beat in this portion is mostly checked for all sort of
ailments. Or so it is believed. Further more the electricity passing out
through outer skin is again reverted to one's own body because of the
ring shaped bangles, which has no ends to pass the energy outside but to
send it back to the body. This way a women gains her strength which is
presumably wasted otherwise. So the ancient Hindus gave shape to this
item called Bangles and later it got molded in to many shapes and
designs to add more attraction and beautification.