The stability ball is one of the most versatile pieces of fitness equipment, and is used by, physical and occupational therapists; yoga and pilates instructors; chiropractors, and other health and fitness professionals, for exercising, strengthening, rehabilitating, specific sports training, and more. It is also used as a replacement to the traditional office chair, as the simple act of sitting on the disc activates core abdominal and trunk muscles, strengthening and toning them throughout the day.