This exercise is suitable for the strengthening of the upper back.
Face the wall. Grab the handles of the plastic cord fixed to the wall bars or to any other adequate equipment, knees slightly bent, bend your torso slightly forward, back is straight. Stand in such distance from the wall so that the cord can be firm all the time. Your arms should be the extension of your torso then pull the cord to the side with bent elbows in such way that you try to close your shoulder blades and you approach your elbows to the back. Try to focus the muscle work to the back muscles during the whole exercise.