An exercise device providing a sling of flexible material forming a cradle supported by a frame so that the cradle is initially taut. The frame is basically a "U" shape fabricated from tube stock. The cradle may be fabricated of canvas with two opposing edges formed as channels into which the frame is...http://www.google.ca/patents/US5125650?utm_source=gb-gplus-sharePatent US5125650 - Flat stomach machine
