What is waist training? Do waist trainers work? Traditionally "waist training" referred to the use of steel boned corsets to develop an exaggerated hourglass shape. By cinching a corset tighter and tighter, the waist trainer corset was able to pull in a woman's floating ribs and even do a bit of rearranging of her internal organs to effectively reduce the circumference of her waist. The effect is semi-permanent, requiring continued corseting even after the goal reduction has been achieved. Not sure which one to buy? Check out our 6 best waist trainers for beginners.