An adjustable leg exercise device is provided which is easily configured for either a power hip, power leg, or hack squat exercise and is adaptable for safe use by athletes of different size and strength. The exercise device preferably includes a pair of parallel, spaced-apart, upwardly inclined rails...http://www.google.fr/patents/US4535985?utm_source=gb-gplus-shareBrevet US4535985 - Power hip, hack squat and leg exercise sled
