A bi-directional exercise machine has a work arm, first and second cams coupled to the work arm, a resistance mechanism, and a pulley assembly that couples the resistance mechanism to the work arm via the first and second cams so that movement of the work arm is resisted by the resistance mechanism according to first and second resistance profiles provided by the first and second cams, respectfully. A primary pulley cable has a first end coupled to the first cam and a second end coupled to the second cam. When the work arm is in a rest position, the ends of the primary pulley cable extend from cable tracks of the cams, respectively, at a tangent so that the resistance mechanism applies a resistance force on the work arm via the pulley assembly immediately upon movement of the work arm out of the rest position.