A weightlifting assistance device, for being mounted on the dedicated squat rack, where the said device is formed from a base, a connector, a top, fixation frames (17, 18), a fixation means designed for the said rack and a gas spring: - where one or more linear guide bushings are locked into the base on one of their side, and extend parallelly toward the connector, where all guide bushings end; - where each linear guide, which emerges from the corresponding liner guide bushing, ends connected to the movable top, allowing the said top to travel from the connector upward for the travel path defined by the used gas spring; - where the bottom fixation frame extends from the base and the top fixation frame extends from the connector, where both frames (17, 18) end into the fixation means and space apart all linear guides from the said fixation means, and - where the movable top is equipped with barbell holder, allowing the said barbell holder to be locked within the said top at the desired position by using a locking means; characterized in that - said gas spring is selected to be a locking gas spring that is formed from the outer cylinder, the piston rod and the release pin capable to activate a valve mechanism via the force exerted to the release pin, and where the said force is transmitted via the valve actuator towards the valve that locks or unlocks the said locking gas spring; - wherein said gas spring outer cylinder is nested within the base and the connector in a manner that the piston rod and the socket (13.1) mounted to the said piston rod, are loosely inserted into the movable top in a way that the release pin, positioned within the piston rod top, is in direct mechanical contact with the movable top and the barbell holder inserted into; and - when the outer force is exerted to the barbell holder in the base direction, it unlocks previously stored mechanical energy within the locking gas spring and enables the said assistance device to produce counterforce by extending the piston rod and movable top with the barbell holder attached thereto in the opposite direction of the applied outer force for times during which the said outer force is exerted, otherwise in absence of the outer force the locking gas spring is locked. - where one or more linear guide bushings are locked into the base on one of their side, and extend parallelly toward the connector, where all guide bushings end; - where each linear guide, which emerges from the corresponding liner guide bushing, ends connected to the movable top, allowing the said top to travel from the connector upward for the travel path defined by the used gas spring; - where the bottom fixation frame extends from the base and the top fixation frame extends from the connector, where both frames (17, 18) end into the fixation means and space apart all linear guides from the said fixation means, and - where the movable top is equipped with barbell holder, allowing the said barbell holder to be locked within the said top at the desired position by using a locking means; - said gas spring is selected to be a locking gas spring that is formed from the outer cylinder, the piston rod and the release pin capable to activate a valve mechanism via the force exerted to the release pin, and where the said force is transmitted via the valve actuator towards the valve that locks or unlocks the said locking gas spring; - wherein said gas spring outer cylinder is nested within the base and the connector in a manner that the piston rod and the socket (13.1) mounted to the said piston rod, are loosely inserted into the movable top in a way that the release pin, positioned within the piston rod top, is in direct mechanical contact with the movable top and the barbell holder inserted into; and - when the outer force is exerted to the barbell holder in the base direction, it unlocks previously stored mechanical energy within the locking gas spring and enables the said assistance device to produce counterforce by extending the piston rod and movable top with the barbell holder attached thereto in the opposite direction of the applied outer force for times during which the said outer force is exerted, otherwise in absence of the outer force the locking gas spring is locked.