Machine External Rotation

Sit at the machine with your working arm resting on the pad, elbow bent to 90 degrees and tucked against your side, gripping the handle out in front of you. Keeping your elbow anchored on the pad, rotate your forearm outward and back against the machine's resistance. The pad keeps your elbow from drifting in a way you'd otherwise have to manage yourself with a cable or dumbbell, so you can focus purely on the rotation. Control the return back to the start rather than letting the stack pull your arm back across your body.