An exercise machine applicable for strengthening a user's abdominal muscles is described. The exercise machine can include a base frame to provide ground support, a mounting assembly rotably mounted over the base frame, a backrest assembly movably coupled to the mounting assembly via one or more pivot joints for swivel movements along the base frame and a handle assembly adjustably affixed to the backrest assembly to allow a user sitting on the seat pad to induce the swivel movements via the backrest assembly.