When they are out of balance the energy can become blocked in one or more of the chakra points. This causes the energetic patterns of the body to flow too quickly or too slowly.
The concept of chakras comes from India and is thousands of years old. Extensive references to the chakra system are in the Upanishads, the Hindu holy books written in 1000 BC. Modern medicine has yet to validate the subtle energetic centers of the chakra system, but we're hoping they catch up soon. In the meantime, those who have balanced their chakras know how powerful these energy centers are.