Mitchell says, hippety-hoppety, get yourself a rope. Jumping rope is good for your muscles, your legs and your heart. Jumping rope, hippety-hoppety, is the best exercise there is. Even if you only do it for five minutes a day. Hippety-hoppety Dr. Kenneth Cooper, author of Aerobics, who invented a point scale to measure exercise effectiveness, rates rope-jumping as the equivalent of jogging a mile or skiing for a half hour. If your joints are feeling creaky, hippety-hoppety, use IT--that's Interval Training. Begin with 15-second bouts of skipping and gradually work yourself up to 500 (!) graceful leaps and pirouettes. ""Observe the principle of progressive overload""--that means jumping until you begin to pant. But first, give up smoking. Mitchell, as enthusiastic about his rope-jumping as Christopher Robin was about his, suggests that it will also take off ugly pounds and inches. If not, you can always use the rope to hang yourself.