The present invention provides a cost-effective, mobile, adjustable, versatile, reliable and easy-to-use exercise sitting apparatus that permits a user to develop, strengthen, stretch, increase the flexibility of and/or rehabilitate, and to eliminate or reduce pain (if present) associated with, a wide variety of muscles and/or body parts, such as the abdominal, lower back, external oblique and/or hip flexor muscles. The user of the exercise sitting apparatus may be of normal health, disabled, suffering from a disease or recovering from an illness, injury, accident or surgery. The exercise sitting apparatus comprises a platform, a turntable assembly, a slide plate assembly, a supporting structure and a base. It can be used virtually anywhere, for example, in a home, an office, a gym, a hospital, a rehabilitative facility, a back pain center, a nursing home or the like.