If you're looking for an exercise that will work both your upper and middle back then you can't go wrong with rows.
People perform rows most commonly using a bench and dumbbells. Start by bending over with your right knee on the bench and your left leg extended to the ground. Grasp the dumbbell with your left hand while placing your right hand on the bench for balance. Lift the dumbbell up so your elbow is bent at a 90-degree angle. Hold for two to three seconds, and then slowly lower your arm. Complete 10 repetitions before moving the dumbbell to your right hand and kneeling on the bench with your left knee [source: Iron Workout]. You can also complete rows in a standing position. Simply bend at the waist as you perform the exercise [source: Body Building].
Want to really increase the intensity? Trade those dumbbells for kettle bells, or large ball-shaped weights with a curved handle on top. They add an extra dimension of instability to the weight. The swaying motion of the kettle bell will increase the difficulty of the exercise and engage more muscles.