Abstract: An exercise device and methods for strengthening the muscles of lower back and abdomen. The device may be configured to impart extension to the spine of a user. The device may include a reclinable chair having a backrest pivotally attached to a seat. The backrest may be pivotally declined backwards in relation to the seat by a user during exercise. The device may include a decline control mechanism that is selectively operable to resist the decline of the backrest, to limit the maximum angle of decline of the backrest relative to the seat, or both.