A novel method and device for exercising the rotary torso muscles of the human body, wherein the device is an exercise machine on which a user's body is supported in a generally supine position. The machine is comprised of a frame structure with a rotatable upper torso support (including a head and back rest), a rotatable lower torso support (including a seat) and feet stabilizing rollers, aligned longitudinally. The device further comprises a knee cushion for rotating the lower torso support and a peg upon a weight support arm for holding free weights that impart resistance against the rotation of the upper and lower torso supports. In an alternate embodiment, additional resistance to the rotation movement is provided by a belt mechanism which wraps around a disk connected to the axle of the upper torso support and up through the weight support arm upon which free weights are placed.