To get the most out of your upper back workouts you must train for both muscle width and thickness. Training the latissimus dorsi muscles on the outsides of the upper back will help give you that width that every weight trainer needs to give them that wide look. Pull-ups and cable pulldowns are the primary width builders in an upper back weight training workout routine. The muscles in the middle of the upper back must also be trained for more thickness. Row exercises are the best to build a thicker back.