Cincinnati Fitness & Boxing's 7,000-square-foot space once held the clatter and clang of a steel mill. Today, the sound of metal on metal has been replaced with the sounds of glove against pad, but much of the industrial charm remains. High windows above exposed brick and cinderblock walls cast light onto two full-sized rings, where welter weights and heavy weights alike learn from instructors as tough as steel. Their ranks include professional boxers, kickboxers, and MMA instructors, all of whom have the experience to carve rock-hard biceps out of any arms. One of their teachers, Marty Slone, once even sparred 100 rounds straight, a staggering accomplishment done to benefit the Juvenile Diabetes Research Foundation.