In the latest (August 2002) issue of "Alternatives for the Health-Conscious Individual" by Dr. David Williams, he talks about some interesting research in vibrations. He says that researchers have found that vibrations or energy currents in the range of 20 to 50 Hz stimulates bone growth. The production of the body's natural anti-inflammatory compounds is increased. Joint pain and swelling improves. Bone fractures heal faster, and weakened bones begin to strengthen and rebuild. http://www.geocities.com/missionstmichael/Purring.html