Ah, the wonderful ways in which we can lose weight without having to do anything; witness the era of vibrating machines. Invented in the late 19th century, by the 1950s, the heyday of vibrating belts had happy housewives jiggling their fat away. And believe it or not, the fad persists, which is the unexpected part. The latest in fat-melting mechanics is the Power Plate, a vibrating platform that its manufacturer promises will help tone muscles in a jiffy, not to mention everything else from enhanced metabolism to reduced cellulite. Sadly, no solid medical evidence has ever been presented to prove the claims.