world boxing champ |GET IN THE RING

hunk! Thunk! Thunk! Left jab. Overhand Rattling left hook. "Take that, you big, ugly, no-talent, go-cry-home-to-Mama ... bag!"

Whether it's dressed up as box-aerobics, cardiobox, slug-mania or one of a dozen other names, the sport of boxing has become a heavyweight in the fitness world. You can now find boxing classes, or some offshoot, in 21 percent of all U.S. health clubs, according to the American Council on Exercise. And that figure is rising.

To discover what all the fuss is about, I went mano-a-mano with 100-bags for one week and learned what so many others before me have already discovered: Boxing delivers a peerless total-body workout--which you don't need to attend a class to get.