This patent discloses a machine to assist a person in strength training. The strength training machine may have a bar supported between two uprights. A motor and mechanisms may cause the bar to move up and down at a constant rate. A person may position themselves above, below, or to a side of the bar. As the bar moves, a person may push or pull against the resistance provided by the moving bar. The motor and mechanisms may prevent the bar from moving in response to the person pressing or pulling against the bar, no matter how hard the person presses or pulls on the bar.