The single-arm machine high row is a machine-based exercise targeting the back muscles, including the lats, rhomboids, and middle and lower traps. It approximates the motion of a free-weight row, but uses a selectorized weight-stack or plate-loaded machine. Many such machines also allow you to choose between different grips and grip widths. Machine-based rows are often done for moderate to high reps, such as 8-12 reps per set or more, as part of the upper-body or back-focused portion of a workout.