A tough, fast-paced program; Karen blends interval step-aerobics with solid muscle toning. You’ll maximize calorie burning and maximize the excitement during her seven sprints. They’re 1-½ to 5-½-minute high-intensity segments alternated between medium-intensity aerobics (just slowing down, never stopping). Squats, propulsions and non-stop large limb movements; it’s challenging because you’re blending intensity with maximum control. You also get classic upper body and ab floorwork. Great cuing (she’s the 1992 IDEA Instructor of the Year). Requires 2 to 8 lb. dumbbells.