The Gravitron 2000 upper-body exercise system is a machine designed for performing lift-assisted pull-up, chin-up, and bar dip exercises. The 180 pound weight stack, divided by 10 pound increments, provides a wide range of assistance levels. The exclusive linear tracking mechanism eliminates the joint stress associated with systems that use a pivotal mechanism. Regular use of the Gravitron 2000 upper-body exercise system develops and strengthens the major muscle groups of the upper body, including the: biceps, brachialis, brachioradialis, deltoid, triceps, pectoralis major and minor, latissimus dorsi, rhomboids, teres major, and trapezius.