Device and methods for strengthening and toning the abdominal and gluteal muscles. A seat is mounted in a fixed position on a base, and a back is pivotally mounted for movement about an axis toward the rear of the seat, with springs or elastic cords yieldably urging the backrest to pivot in an upward direction toward a raised position. To strengthen and condition the upper, lateral and oblique abdominal muscles and gluteal muscles, an exerciser rests upon the seat, with his back against the backrest, and the elastic cords or springs assist him in raising his back and also allow him to extend to the full range of backward motion while absorbing the impact of that motion. To exercise the lower abdominal muscles and gluteal muscles, the exerciser reclines on the seat, with his legs on the backrest and the elastic cords or springs assisting him in raising his legs and absorbing the impact of lowering them.